Passing Traits to Offspring - Middle School Life Science

1. Using a Punnett square, what fraction of offspring are heterozygous from $AA \times aa$?

   $1$ (all are $Aa$). All offspring get $A$ from one parent and $a$ from the other.

2. Identify the genotype type: Is genotype AA homozygous or heterozygous?

   Homozygous. Same alleles make it homozygous.

3. What is a dominant allele in a simple dominant-recessive model?

   An allele expressed in a heterozygote. Dominant alleles mask recessive ones when paired together.

4. Using a Punnett square, what is the probability of $aa$ offspring from $Aa \times Aa$?

   $\frac{1}{4}$. One of four boxes in the Punnett square is $aa$.

5. What is the phenotype of an organism?

   Its observable trait or appearance. Phenotype is the physical expression of the genotype.

6. Using a Punnett square, what is the genotype ratio for the cross Aa × Aa?

   $1$ AA : $2$ Aa : $1$ aa. Punnett square shows $\frac{1}{4}$ AA, $\frac{2}{4}$ Aa, $\frac{1}{4}$ aa.

7. Which genotype(s) produce the recessive phenotype when $A$ is dominant over $a$?

   Only $aa$. Two recessive alleles needed for recessive trait.

8. What is an allele?

   An alternative form of a gene. Different versions of the same gene create variation in traits.

9. In simple dominance with $A$ dominant, what phenotype ratio results from $Aa \times Aa$?

   $3$ dominant : $1$ recessive. $AA$ and $Aa$ show dominant; only $aa$ shows recessive.

10. What does homozygous mean?

    Two identical alleles for a gene. Both alleles are the same version of the gene.

11. Using a Punnett square, what fraction of offspring are expected to be aa from Aa × Aa?

    $\frac{1}{4}$. One box out of four in the Punnett square contains aa.

12. What fraction of gametes from an Aa parent carry allele A in a simple model?

    $\frac{1}{2}$. Each allele has equal chance during gamete formation.

13. What is the model called that uses a grid to predict offspring genotypes from parent alleles?

    Punnett square. A grid showing all possible genetic combinations from parents.

14. What is an allele in a heredity model?

    An alternative form of a gene. Alleles are different versions of the same gene, like brown vs blue for eye color.

15. What is the genotype of an organism?

    Its allele combination for a trait. Genotype refers to the genetic makeup, not physical appearance.

16. What is a phenotype?

    The observable trait produced by genotype and environment. Genotype interacts with environment to produce traits.

17. Identify the phenotype ratio for Aa × Aa when A is dominant over a.

    3 dominant : 1 recessive. Three show dominant phenotype, one shows recessive.

18. What is the term for different versions of the same gene (for example, for eye color)?

    Alleles. Different forms of a gene that produce trait variations.

19. What are the possible gametes made by a heterozygous parent with genotype Aa?

    A and a. Each gamete gets one allele during meiosis.

20. What is the difference between genotype probability and phenotype probability in a Punnett model?

    Genotype: allele combo chance; phenotype: trait chance. Genotype probability is for specific allele combos; phenotype is for trait expression.

21. What is the purpose of a Punnett square model?

    To predict offspring genotype and phenotype probabilities. Shows all possible genetic combinations from parents.

22. Identify the expected genotype ratio for the cross AA × aa.

    $100\%$ Aa. All offspring get A from one parent and a from the other.

23. What does it mean if an organism is homozygous for a gene?

    It has two identical alleles for that gene. Homozygous means both inherited alleles are the same, like AA or aa.

24. What is fertilization modeled to explain in inheritance?

    How two gametes combine to restore two alleles. Fusion creates offspring with complete genetic information.

25. Which gametes can a heterozygous parent (Aa) produce for that gene?

    A and a. Heterozygotes produce equal amounts of both allele types.

26. What genotype term describes two different alleles for a gene (for example, $Bb$)?

    Heterozygous. Having two different alleles for the same gene.

27. What is an allele?

    An alternative form of a gene. Different versions of the same gene create variation in traits.

28. What does recessive mean in a simple dominance model?

    An allele expressed only when two copies are present. Hidden by dominant alleles unless homozygous.

29. What do the terms dominant and recessive describe in simple Mendelian models?

    Which allele is expressed in a heterozygote. Dominant masks recessive in heterozygotes.

30. What do the letters in a Punnett square represent?

    Alleles carried in gametes and offspring combinations. Letters show which alleles parents pass and possible offspring combinations.

31. What is the term for a version of a gene that can produce different forms of a trait?

    Allele. Different versions of the same gene create variation in traits.

32. Using a Punnett square, what fraction of offspring show the recessive phenotype in $Bb \times Bb$?

    $\frac{1}{4}$. Only $bb$ offspring (1 of 4 boxes) show recessive trait.

33. Identify the expected genotype ratio from a cross $AA \times aa$.

    $100\%$ $Aa$. All offspring inherit $A$ from one parent and $a$ from the other.

34. What is the term for a cell with two sets of chromosomes (two alleles per gene)?

    Diploid. Having two complete sets of chromosomes (2n).

35. What is fertilization in a heredity model?

    Fusion of two gametes to form a zygote. Fertilization combines genetic material from both parents' gametes.

36. What is fertilization in a heredity model?

    Fusion of two gametes to form a diploid zygote. Fertilization restores the full chromosome number in offspring.

37. Using a Punnett square, what fraction of offspring show the dominant phenotype from Aa × Aa?

    $\frac{3}{4}$. Three boxes (AA, Aa, Aa) show dominant trait, one (aa) shows recessive.

38. In a Punnett square, what do the letters placed on the outside represent?

    The alleles in the parents' gametes. These show which alleles each parent can pass on.

39. What is the difference between dominant and recessive alleles in a model?

    Dominant is expressed in Aa; recessive needs aa. Dominant masks recessive in heterozygotes; recessive appears only when homozygous.

40. What is a Punnett square used to model?

    Possible offspring genotypes from a genetic cross. Shows all possible genetic combinations from parent crosses.

41. What is a gene?

    A DNA segment that codes for a trait or protein. Genes are hereditary units that determine specific characteristics.

42. Using a Punnett square, what is the probability of recessive phenotype from $Aa \times aa$ when $A$ is dominant?

    $\frac{1}{2}$. Half the offspring inherit $aa$ from the $aa$ parent.

43. What is the term for an allele that is masked by a dominant allele in a heterozygote?

    Recessive allele. Only expressed when paired with an identical allele.

44. What is the name of the model used to predict offspring genotypes from parental alleles?

    Punnett square. This grid shows all possible offspring genotype combinations.

45. What model statement best describes Mendel's law of segregation?

    Allele pairs separate during gamete formation. Each parent contributes only one allele per gene to each gamete.

46. What is a genotype?

    The allele combination an organism has. Genotype refers to the genetic makeup, not the visible trait.

47. Using a simple dominance model, what is the phenotype ratio for $Aa \times Aa$ when $A$ is dominant?

    $3$ dominant : $1$ recessive. $AA$ and $Aa$ show dominant; only $aa$ shows recessive.

48. What is the name of the process that makes gametes with half the usual number of chromosomes?

    Meiosis. Cell division that reduces chromosome number from diploid to haploid.

49. What process makes gametes and separates allele pairs into different cells?

    Meiosis. Cell division that halves chromosome number for sexual reproduction.

50. What is the probability of aa offspring from a cross Aa × Aa?

    $\frac{1}{4}$. One in four offspring inherit both recessive alleles.

51. Which sex cell type is a gamete that carries genetic information from the male parent?

    Sperm cell. Male gamete that fuses with egg cell during fertilization.

52. What genotype term describes having two different alleles for a gene (for example, $Aa$)?

    Heterozygous. One dominant and one recessive allele create this mixed genotype.

53. What does a Punnett square model show?

    Possible offspring genotypes from parental gametes. This grid predicts offspring traits by combining parent gametes.

54. What does it mean if an organism is homozygous for a gene?

    It has two identical alleles (for example, AA or aa). Both alleles are the same version of the gene.

55. What is the term for an organism's allele combination for a trait (for example, $Bb$)?

    Genotype. The genetic makeup showing which alleles an organism has.

56. What is the term for sex cells that carry one allele for each gene and form by meiosis?

    Gametes. Sex cells (sperm and egg) with half the genetic material.

57. What is the key rule of allele separation during gamete formation (meiosis)?

    Each gamete receives only one allele per gene. This is Mendel's Law of Segregation during meiosis.

58. What is the genotype of an organism?

    The allele combination an organism has. Genotype represents the genetic makeup, written as letter combinations like Aa.

59. What model best represents that offspring receive one allele from each parent?

    A Punnett square showing one allele per gamete. Shows gametes with single alleles combining at fertilization.

60. What is phenotype?

    The observable trait produced by genotype and environment. What you see results from genes plus environment.

61. Identify the expected genotype ratio from a monohybrid cross Aa × Aa.

    $1$ AA : $2$ Aa : $1$ aa. Classic Mendelian ratio from heterozygous parents.

62. What is the definition of a test cross used with dominant phenotypes?

    Cross with homozygous recessive to infer genotype. Reveals whether dominant phenotype is AA or Aa.

63. What is phenotype?

    The observable trait produced by genotype and environment. What you see, like brown eyes, determined by genes plus environment.

64. In a Punnett square, what do the letters along the top and side represent?

    The alleles in each parent's gametes. Each gamete contributes one allele to offspring.

65. Identify the expected phenotype from a cross $AA \times aa$ if $A$ is dominant.

    All offspring show the dominant phenotype. All offspring are $Aa$, so all express the dominant trait.

66. What does the law of segregation state about allele pairs during gamete formation?

    Allele pairs separate so each gamete gets one allele. During meiosis, allele pairs split up into separate gametes.

67. Using a model, what are the possible gametes from a heterozygous parent Aa?

    A and a. Heterozygous parents can produce gametes with either allele they carry.

68. What is fertilization in the model of inheritance from parents to offspring?

    Fusion of two gametes to form a zygote with full chromosomes. It restores the diploid chromosome number.

69. What do the terms genotype probability and phenotype probability mean in Punnett models?

    Chance of allele pair vs chance of expressed trait. Genotype is genetic makeup; phenotype is physical trait.

70. What is a gene?

    A DNA segment that codes for a trait or protein. Genes are instructions in DNA that determine specific characteristics.

71. What fraction of offspring are expected to be $Aa$ from a cross $AA aa$?

    $1$ (all offspring are $Aa$). All offspring inherit $A$ from one parent and $a$ from the other.

72. What is a dominant allele in simple Mendelian models?

    An allele expressed with one copy in a heterozygote. Dominant alleles mask recessive ones when paired together.

73. What are the possible gametes from a heterozygous parent with genotype $Aa$?

    $A$ and $a$. Each gamete gets one allele from the pair.

74. What is the phenotype of an organism?

    Its observable traits. Physical characteristics result from genotype expression.

75. Identify the offspring genotype outcome pattern for a test cross $Aa \times aa$.

    $\frac{1}{2}$ Aa and $\frac{1}{2}$ aa. Half inherit A from heterozygous parent, half inherit a.

76. What probability of alleles does each parent contribute to one offspring for one gene?

    Each parent contributes $\frac{1}{2}$ of the alleles (one of two). Each parent gives one allele per gene pair.

77. Which offspring genotypes are possible from a cross $AA\times aa$?

    All offspring are $Aa$. Homozygous parents produce uniform offspring.

78. In a Punnett square, what fraction of alleles for a gene does each parent contribute to an offspring?

    Each parent contributes $\frac{1}{2}$ of the alleles. Each parent's gamete contributes one allele, making half the total.

79. Which offspring phenotype is possible from a cross $AA\times aa$ with complete dominance?

    Only the dominant phenotype. All $Aa$ offspring express dominant trait.

80. Which option states the probability of offspring genotype aa from $Aa \times Aa$?

    $\frac{1}{4}$. One out of four boxes shows aa genotype.

81. What is a gene?

    A DNA segment that codes for a trait. Genes are hereditary units on chromosomes.

82. Which model tool is used to predict offspring genotypes from parent alleles?

    A Punnett square. This grid shows all possible offspring combinations.

83. Identify the probability of a recessive phenotype from Aa × aa when A is dominant.

    $\frac{1}{2}$. Half the offspring inherit two recessive alleles.

84. What is a gene?

    A DNA segment that codes for a trait. Genes are specific DNA sequences that determine inherited characteristics.

85. What does homozygous mean?

    Having two identical alleles for a gene. Both alleles are the same version of the gene.

86. What is the definition of genotype in a trait model?

    The allele combination an organism has. Genotype represents the genetic makeup, not the visible trait.

87. What is fertilization in inheritance models?

    Fusion of two gametes to form a zygote. Gametes unite to restore the diploid chromosome number.

88. What does it mean if an organism is heterozygous for a gene?

    It has two different alleles for that gene. Heterozygous means the two inherited alleles differ, like Aa.

89. Identify the genotype ratio for Aa × Aa (complete dominance).

    1 AA : 2 Aa : 1 aa. This is the classic Mendelian monohybrid cross ratio.

90. What does it mean if a trait shows incomplete dominance in a model?

    Heterozygote shows an intermediate phenotype. Neither allele is fully dominant, creating a blended trait.

91. Identify the probability of recessive phenotype from $Aa\times Aa$ with complete dominance.

    $\frac{1}{4}$. Only $aa$ genotype ($\frac{1}{4}$) shows recessive trait.

92. What is a gamete in a heredity model?

    A sex cell with one allele for each gene. Gametes carry half the genetic information, one allele per gene pair.

93. What is the role of gametes in inheritance models?

    They carry one allele for each gene to offspring. Gametes are sex cells that combine genetic information from both parents.

94. What is the phenotype of an organism?

    The observable trait produced by genes and environment. Phenotype is what you can see or measure, resulting from genes plus environment.

95. What is the purpose of a Punnett square model?

    To predict possible offspring genotypes and probabilities. It shows all possible genetic combinations from a cross.

96. What does it mean if an organism is heterozygous for a gene?

    It has two different alleles for that gene. The two alleles differ (e.g., $Aa$).

97. What is a gene?

    A DNA segment that codes for a trait. Genes are hereditary units on chromosomes.

98. What is the term for a segment of DNA that contains instructions for a trait?

    Gene. A gene is a DNA segment that codes for a specific trait.

99. What genotype term describes having two identical alleles for a gene (for example, $AA$)?

    Homozygous. Both alleles are the same, either both dominant or both recessive.

100. What is a carrier in a recessive-trait model?

     A heterozygote that can pass a recessive allele. Has recessive allele but shows dominant phenotype.

101. Identify the offspring genotype ratio for Aa × Aa using a Punnett square.

     $1$ AA : $2$ Aa : $1$ aa. Cross produces $\frac{1}{4}$ AA, $\frac{2}{4}$ Aa, $\frac{1}{4}$ aa.

102. What is a gene?

     A DNA segment that codes for a trait. Genes are hereditary units that determine specific characteristics.

103. Identify the genotype produced by combining gametes A and a.

     Aa. One allele from each parent combines to form heterozygous offspring.

104. Using a Punnett square, what is the genotype ratio for $Aa \times Aa$?

     $1\ AA : 2\ Aa : 1\ aa$. The cross produces $\frac{1}{4}$ $AA$, $\frac{1}{2}$ $Aa$, $\frac{1}{4}$ $aa$.

105. What is a gene in a heredity model?

     A DNA segment that codes for a trait. Genes are the basic units of heredity that determine specific characteristics.

106. What is the probability that a parent passes a particular allele in a simple model?

     $\frac{1}{2}$ for each allele in a heterozygous parent. Each gamete gets one allele randomly.

107. What is a phenotype?

     The observable trait produced by genotype and environment. Phenotype is what you see, influenced by both genes and environment.

108. What is a Punnett square used to model?

     Possible offspring genotypes and their probabilities. This grid shows all possible genetic combinations from parent crosses.

109. Using a Punnett square, what is the genotype ratio for $Aa \times Aa$?

     $1$ $AA$ : $2$ $Aa$ : $1$ $aa$. Classic Mendelian ratio from heterozygous cross.

110. What is a genotype?

     The allele combination an organism has. Written as letter pairs like $Aa$ or $BB$.

111. Using a Punnett square, what fraction of offspring show the dominant phenotype from $AA \times aa$?

     $1$ (all show the dominant phenotype). All offspring have at least one dominant $A$ allele.

112. What is the probability that a parent passes a specific allele in a gamete?

     Each allele has probability $\frac{1}{2}$ of being passed. Random segregation gives equal chance to each allele.

113. What does dominant mean in a simple dominance model?

     An allele expressed when at least one copy is present. Capital letters show dominance over lowercase.

114. What is the definition of recessive allele in Mendelian models?

     An allele expressed only with two copies. Recessive traits appear only in homozygous individuals.

115. Which statement matches Mendel's law of segregation?

     Allele pairs separate during gamete formation. Each parent contributes only one allele per gene to offspring.

116. In a Punnett square, what does each parent contribute for a single gene to each offspring?

     One allele. Each gamete carries one allele, combining at fertilization.

117. Using a Punnett square, what is the probability of heterozygous offspring from $AA \times aa$?

     $1$ (or $100\%$) are $Aa$. All offspring get $A$ from one parent, $a$ from other.

118. What genotype is heterozygous?

     Two different alleles (Aa). Heterozygous means having non-matching alleles for a gene.

119. What is the term for the observable expression of a trait (for example, brown eyes)?

     Phenotype. The physical trait results from the genotype's expression.

120. What is a dominant allele in a simple dominance model?

     An allele expressed when at least one copy is present. It masks the recessive allele in heterozygotes.

121. Identify the offspring phenotype ratio for Aa × Aa when A is dominant.

     $3$ dominant : $1$ recessive. AA and Aa show dominant trait; only aa shows recessive.

122. Using a Punnett square, what fraction of offspring are $aa$ from $Aa \times Aa$?

     $\frac{1}{4}$. One box out of four shows $aa$ genotype.

123. Using a Punnett square, what offspring genotype ratio results from $Bb \times Bb$?

     $1\,BB : 2\,Bb : 1\,bb$. Each parent contributes $B$ or $b$ with equal probability.

124. What does it mean if an organism is heterozygous for a gene?

     It has two different alleles (for example, Aa). Heterozygous means having one dominant and one recessive allele.

125. What is an allele?

     An alternative form of the same gene. Alleles are variations of a gene that produce different traits.

126. What fraction of offspring are expected to be $aa$ from $Aa \times Aa$?

     $\frac{1}{4}$. One out of four boxes in the Punnett square shows $aa$.

127. What is the definition of a gene in a heredity model?

     A DNA segment that codes for a trait. Genes are specific DNA sequences that determine inherited characteristics.

128. What is the term for an organism's allele combination for a trait (for example, $Aa$)?

     Genotype. The genetic makeup determines which alleles an organism carries.

129. What is a recessive allele in a simple model of inheritance?

     An allele expressed only when homozygous. Both copies must be recessive to show the trait.

130. Using a Punnett square, what fraction of offspring show the recessive phenotype from $Aa \times Aa$?

     $\frac{1}{4}$. Only $aa$ offspring show recessive trait (1 of 4 boxes).

131. What does each box in a Punnett square represent?

     One possible allele combination for an offspring. Shows the genotype from combining one gamete from each parent.

132. What does heterozygous mean?

     Having two different alleles (Aa). One dominant and one recessive allele create a mixed genotype.

133. Which statement describes meiosis in inheritance models?

     It makes gametes with one allele per gene. Meiosis halves chromosome number, creating haploid gametes.

134. Using a Punnett square, what is the probability of heterozygous offspring from $Aa \times Aa$?

     $\frac{1}{2}$. Two of four boxes show $Aa$ genotype.

135. What is genotype?

     The allele combination an organism has. Genotype refers to the genetic makeup, like AA, Aa, or aa for a trait.

136. What is a dominant allele in simple Mendelian inheritance?

     An allele expressed in a heterozygote. It masks the recessive allele when both are present.

137. Identify the correct phenotype ratio for $Aa \times Aa$ when A is dominant.

     $3:1$ (dominant:recessive). Three show dominant trait, one shows recessive.

138. What is a gamete, and how many alleles for a gene does it carry?

     A sex cell; it carries $1$ allele per gene. Gametes (sperm/egg) carry half the genetic information.

139. What does it mean if an organism is homozygous for a gene?

     It has two identical alleles (AA or aa). Homozygous means both alleles are the same type.

140. Which phenotype is expected if genotype is $Aa$ and $A$ is dominant over $a$?

     Dominant phenotype. Dominant allele $A$ masks recessive $a$ in heterozygotes.

141. Identify the genotype: If an organism has alleles A and a, what is its genotype notation?

     Aa. Capital letter first, lowercase second by convention.

142. What is genotype?

     The allele combination an organism has for a trait. Like AA, Aa, or aa - the genetic makeup for a specific trait.

143. Identify the genotype ratio from a cross $Aa \times Aa$.

     $1\,AA : 2\,Aa : 1\,aa$. Results from combining $A$ and $a$ gametes in all possible ways.

144. Identify the phenotype in a simple model if genotype is $Aa$ and $A$ is dominant.

     Dominant phenotype. The dominant $A$ allele determines the visible trait.

145. What fraction of offspring are expected to be heterozygous from $Aa \times Aa$?

     $\frac{1}{2}$. Two out of four boxes in the Punnett square show $Aa$.

146. What is meiosis mainly modeled to explain in inheritance?

     How gametes get one allele per gene. Cell division that halves chromosome number for reproduction.

147. Identify the phenotype for genotype Aa if A is dominant over a.

     Dominant phenotype. A is dominant, so Aa individuals show A's trait.

148. Identify the genotype produced by crossing gametes A and a in a Punnett square cell.

     Aa. Combining A from one parent and a from the other produces heterozygous Aa.

149. What is the definition of dominant allele in Mendelian models?

     An allele expressed when at least one is present. Dominant alleles mask recessive alleles in heterozygotes.

150. What is the term for the observable trait produced by genotype and environment (for example, brown eyes)?

     Phenotype. The physical expression of genes influenced by environment.

151. What is the definition of an allele in genetic models?

     A different version of the same gene. Alleles are variations that produce different forms of the same trait.

152. What is the purpose of a Punnett square model?

     To predict offspring genotype and phenotype probabilities. Shows all possible offspring combinations.

153. What is genotype?

     An organism's allele combination for a trait. Genotype is the genetic makeup that determines potential traits.

154. What does recessive mean in a simple inheritance model?

     An allele expressed only when two copies are present. Recessive traits only appear when no dominant allele is present (aa).

155. What is the difference between genotype and phenotype?

     Genotype = alleles; phenotype = observable trait. Genotype is genetic makeup; phenotype is physical expression.

156. What does it mean if an organism is homozygous for a gene?

     It has two identical alleles for that gene. Both alleles are the same (e.g., $AA$ or $aa$).

157. What is the expected genotype ratio from a cross $Aa Aa$ (list as $AA:Aa:aa$)?

     $1:2:1$. Punnett square yields 1 $AA$, 2 $Aa$, and 1 $aa$ offspring.

158. What is a gamete, and how many alleles for a gene does it carry?

     A sex cell; it carries one allele per gene. Sperm or egg cells carry half the genetic info.

159. Which statement best describes why siblings can have different traits from the same parents?

     Gametes carry different allele combinations by chance. Random assortment creates unique combinations each time.

160. What is the purpose of a Punnett square model?

     To predict offspring genotype and phenotype probabilities. Shows all possible genetic combinations from parent crosses.

161. What is a Punnett square used to model?

     Possible offspring genotypes from parents. Shows all possible genetic combinations from a cross.

162. What genotype term means two different alleles for a gene?

     Heterozygous. Different alleles like $Aa$.

163. Which statement best describes Mendel's law of segregation?

     Allele pairs separate during gamete formation. Each parent passes only one allele per gene to offspring through gametes.

164. Which genotype(s) produce the dominant phenotype when $B$ is dominant over $b$?

     $BB$ and $Bb$. Dominant allele $B$ is expressed in both genotypes.

165. Identify the phenotype ratio from a cross $Aa \times Aa$ if $A$ is dominant.

     $3$ dominant : $1$ recessive. Three genotypes ($AA$, $Aa$, $aa$) produce two phenotypes when $A$ dominates.

166. What is a gene?

     A DNA segment that codes for a trait. Genes are specific DNA sequences that determine inherited characteristics.

167. What is the probability of dominant phenotype offspring from a cross Aa × aa?

     $\frac{1}{2}$. Half the offspring (Aa) show dominant phenotype.

168. What is meiosis in a model of passing genetic information?

     Cell division that makes haploid gametes. Meiosis reduces chromosome number by half to create sex cells.

169. Identify the genotype of an organism with alleles $A$ and $a$.

     Heterozygous ($Aa$). Different alleles ($A$ and $a$) make it heterozygous.

170. Using a Punnett square, what fraction of offspring show the dominant phenotype in $Bb \times bb$?

     $\frac{1}{2}$. $Bb$ offspring show dominant trait; $bb$ show recessive.

171. What does it mean if an allele is recessive?

     It is expressed only when two recessive alleles are present. Hidden by dominant alleles unless paired with another recessive.

172. What is a recessive allele in a simple dominant-recessive model?

     An allele expressed only when homozygous. Recessive traits only appear when no dominant allele is present.

173. What is the expected phenotype ratio for complete dominance in Aa × Aa?

     $3$ dominant : $1$ recessive. Three genotypes (AA, Aa, Aa) show dominant; one (aa) shows recessive.

174. What is a gene?

     A DNA segment that contains instructions for a trait. Genes are the basic units of heredity.

175. What is meiosis in the model of inheritance from parents to offspring?

     Cell division that makes gametes with half the chromosomes. It reduces chromosome number from diploid to haploid.

176. What process explains why offspring receive one allele for a gene from each parent?

     Meiosis produces gametes with one allele per gene. Gametes carry half the genetic information.

177. Identify the phenotype for genotype aa when A is dominant and a is recessive.

     Recessive phenotype. Two recessive alleles (aa) produce the recessive trait appearance.

178. What is a chromosome?

     A DNA-protein structure carrying many genes. Chromosomes package and organize genetic information for inheritance.

179. Identify the probability of recessive genotype $aa$ from $Aa\times aa$.

     $\frac{1}{2}$. Half the offspring inherit $a$ from both parents.

180. Which model statement is correct: each parent contributes $\frac{1}{2}$ of an offspring's chromosomes, or $\frac{1}{4}$?

     Each parent contributes $\frac{1}{2}$. Each parent gives one set of chromosomes to offspring.

181. Identify the genotype produced by crossing AA and aa (complete dominance).

     All offspring are Aa. Each parent contributes one different allele to all offspring.

182. What does dominant mean in a simple inheritance model?

     An allele expressed when at least one copy is present. Dominant alleles show their effect even with just one copy (Aa or AA).

183. What is a recessive allele in simple Mendelian models?

     An allele expressed only with two copies. Recessive traits only appear when no dominant allele is present.

184. Which allele(s) can a heterozygous parent $Aa$ place in a gamete?

     A or a. Each gamete gets only one allele from each gene pair during meiosis.

185. What does it mean if an allele is dominant?

     It is expressed in the phenotype when at least one is present. Dominant alleles mask recessive ones, like A masking a.

186. Which process makes gametes with half the usual chromosome number?

     Meiosis. Gametes are haploid, containing one set of chromosomes.

187. What is phenotype?

     The observable trait produced by genotype and environment. Phenotype results from both genetic and environmental factors.

188. What is fertilization in genetic inheritance models?

     Union of two gametes to form a zygote. Gametes fuse to restore the diploid chromosome number.

189. What is the term for an allele that masks another allele in a heterozygote?

     Dominant allele. Expressed even when paired with a different allele.

190. What is a zygote in a heredity model?

     A fertilized egg with $2$ alleles per gene. Gets one allele from each parent, restoring the full genetic set.

191. What is a Punnett square used to model?

     Possible offspring genotypes and phenotypes. It predicts genetic outcomes from parental crosses.

192. What is phenotype?

     The observable trait produced by genes and environment. Phenotype is what you see, influenced by both genetics and environment.

193. What does heterozygous mean?

     Having two different alleles for a gene. The two alleles are different versions of the gene.

194. What is a dominant allele in a simple model of inheritance?

     An allele expressed in a heterozygote. It masks the recessive allele's effect when paired together.

195. What does it mean if an organism is heterozygous for a gene?

     It has two different alleles (for example, Aa). The two alleles are different versions of the gene.

196. Which probability is correct for aa offspring from Aa × Aa?

     $\frac{1}{4}$. One out of four offspring will be homozygous recessive.

197. What genotype is homozygous?

     Two identical alleles (AA or aa). Homozygous means having matching alleles for a gene.

198. What does it mean if an allele is recessive?

     It is expressed only with two recessive copies. Recessive traits appear only in homozygous recessive individuals.

199. Identify the model statement that best explains why siblings can differ in traits.

     Different allele combinations form by random gamete union. Random fertilization creates genetic diversity.

200. What is the name of the process in which an egg and sperm join to form a zygote?

     Fertilization. Combines genetic material from both parents to restore diploid number.

201. What is the term for an allele that masks another allele when both are present?

     Dominant allele. This allele's trait appears even with just one copy present.

202. What genotype term means two identical alleles for a gene?

     Homozygous. Same alleles like $AA$ or $aa$.

203. Identify the genotype of an offspring that receives allele $A$ from one parent and $a$ from the other.

     $Aa$. Combines one allele from each parent to form the offspring genotype.

204. What fraction of an offspring's alleles for a gene comes from each parent?

     Each parent contributes $\frac{1}{2}$ of the alleles. Sexual reproduction ensures equal genetic contribution from both parents.

205. Which phenotype is predicted for Aa if A is dominant over a in a simple Mendelian model?

     The dominant phenotype. Dominant allele A determines the phenotype over recessive a.

206. Using a Punnett square, what fraction of offspring are heterozygous in $Bb \times Bb$?

     $\frac{1}{2}$. Two of four boxes ($Bb$) have different alleles.

207. Identify the correct genotype for a recessive phenotype when $A$ is dominant over $a$.

     $aa$. Recessive traits only appear with two recessive alleles.

208. Identify the probability of heterozygous offspring from $Aa\times Aa$.

     $\frac{1}{2}$. Two of four boxes show $Aa$ genotype.

209. What is a gamete, and how many alleles for a gene does it carry?

     A sex cell; it carries one allele per gene. Sperm or egg cells have half the genetic information.

210. Identify the genotype of an offspring that must show a recessive trait.

     aa. Recessive traits only appear with two recessive alleles.

211. What fraction of offspring are expected to be aa from a cross Aa × Aa?

     $\frac{1}{4}$. Punnett square shows 1 aa out of 4 possible outcomes.

212. What is the definition of a gamete in inheritance models?

     A sex cell with one allele for each gene. Gametes are haploid, carrying half the genetic information.

213. What is a recessive allele in simple Mendelian inheritance?

     An allele expressed only when homozygous. Hidden by dominant allele; needs two copies to show.

214. Which gametes can a parent with genotype $Aa$ produce in a simple model?

     $A$ and $a$. Each gamete gets one allele due to segregation.

215. What does homozygous mean?

     Having two identical alleles (AA or aa). Both alleles are the same, either both dominant or both recessive.

216. Which option states the probability of a dominant phenotype from $Aa \times Aa$?

     $\frac{3}{4}$. AA, Aa, and Aa all express the dominant phenotype.

217. What is the difference between genotype and phenotype?

     Genotype = alleles; phenotype = observed trait. Genotype is genetic makeup; phenotype is the physical expression.

218. What is the term for the process that separates allele pairs into different gametes?

     Meiosis. Cell division that halves chromosome number to form gametes.

219. What is the term for the joining of egg and sperm that restores a diploid chromosome number?

     Fertilization. Fusion of gametes that combines genetic material.

220. What does each parent contribute for each gene in most sexual reproduction models?

     One allele. Sexual reproduction combines one allele from each parent.

221. What is the term for a cell with one set of chromosomes (one allele per gene), like a gamete?

     Haploid. Having one complete set of chromosomes (n).

222. What is the definition of phenotype in a trait model?

     The observable trait expressed. Phenotype is the physical manifestation of the genotype.

223. What is meant by segregation in models of inheritance?

     Allele pairs separate into different gametes. During gamete formation, paired alleles split up.

224. What does it mean if an allele is dominant?

     It is expressed when at least one copy is present. Dominant alleles mask recessive alleles in heterozygotes.

225. Which word names a sex cell that carries one set of chromosomes?

     Gamete. Sperm and egg cells are haploid reproductive cells.

226. Using a Punnett square, what is the probability of $aa$ offspring from $Aa \times Aa$?

     $\frac{1}{4}$. One of four boxes in the Punnett square shows $aa$.

227. What is a Punnett square used to model?

     Possible offspring genotypes from parental gametes. The square shows all possible genetic combinations from parent gametes.

228. What is an allele in a genetics model?

     An alternative form of a gene. Alleles are different versions of the same gene, like brown vs. blue eye color.

229. Identify the correct genotype ratio predicted by a Punnett square for $Aa \times Aa$.

     $1:2:1$ (AA:Aa:aa). One AA, two Aa, and one aa from monohybrid cross.

230. What is fertilization in inheritance models?

     Fusion of two gametes forming a zygote. Combines genetic material from both parents.

231. What does heterozygous mean?

     Two different alleles for a gene. One of each version creates genetic variation.

232. What genotype term describes two identical alleles for a gene (for example, $BB$ or $bb$)?

     Homozygous. Having two copies of the same allele for a gene.

233. Which model best shows that siblings can inherit different allele combinations?

     Multiple Punnett square outcomes from the same cross. Each box represents a different possible offspring combination.

234. Identify the law that states alleles separate into different gametes.

     Law of Segregation. Mendel's first law explains gamete formation.

235. In a Punnett square, what do the letters on the outside represent?

     Possible gametes (alleles) from each parent. Each parent's alleles that can be passed on.

236. What is an allele?

     An alternative form of the same gene. Different versions create genetic variation.

237. What is genotype?

     The allele combination an organism has. Written as letter pairs like $AA$, $Aa$, or $aa$.

238. What is a recessive allele in a simple dominance model?

     An allele expressed only when two copies are present. It's masked by dominant alleles in heterozygotes.

239. Identify the offspring genotype ratio for a cross $Aa\times Aa$.

     $1\,AA:2\,Aa:1\,aa$. Results from combining $\frac{1}{2}A:\frac{1}{2}a$ from each parent.

240. What is fertilization in a heredity model?

     Fusion of two gametes to form a zygote. Sperm and egg unite, combining their genetic information.

241. Which genotype produces the recessive phenotype when $B$ is dominant over $b$?

     $bb$. Two recessive alleles needed for recessive trait expression.

242. What is the term for an allele that is masked by a dominant allele in a heterozygote?

     Recessive allele. Needs two copies to show its trait; hidden by dominant alleles.

243. What is a gene?

     A DNA segment that codes for a trait. Genes are hereditary units that determine specific characteristics.

244. Identify the phenotype ratio (complete dominance) for a cross $Aa\times Aa$.

     $3$ dominant : $1$ recessive. Three genotypes ($AA$, $Aa$, $aa$) show dominant trait.

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