Biology Flashcards: Relate Genes To Trait Inheritance

What this deck covers

This deck focuses on Relate Genes To Trait Inheritance, giving you a quick way to review the definitions, rules, and examples that matter most for Biology.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Which term describes a cross involving one gene with two alleles?

Answer: Monohybrid cross. Focuses on inheritance of a single trait.

Flashcard 2: What fraction of offspring are expected to be heterozygous in $Aa \times Aa$?

Answer: $\frac{1}{2}$. Half the offspring inherit one allele from each parent.

Flashcard 3: Identify the genotype of the tester parent in a standard Mendelian test cross.

Answer: Homozygous recessive. The known genotype that reveals the unknown parent's genetics.

Flashcard 4: What is a dominant allele in simple Mendelian inheritance?

Answer: An allele expressed in the heterozygous phenotype. Usually written in uppercase and masks recessive alleles.

Flashcard 5: What is the expected phenotypic ratio from $AaBb \times AaBb$ with independent assortment?

Answer: $9:3:3:1$. Classic ratio for two independent traits with complete dominance.

Flashcard 6: In X-linked inheritance, which parent passes an X chromosome to all daughters?

Answer: The father. All daughters inherit father's X and one maternal X chromosome.

Flashcard 7: What is an autosomal recessive inheritance pattern typically characterized by in pedigrees?

Answer: Trait can skip generations; affected individuals may have unaffected parents. Recessive traits often appear to skip generations in pedigrees.

Flashcard 8: What fraction of offspring are expected to show the recessive phenotype in $Aa \times Aa$?

Answer: $\frac{1}{4}$. Only homozygous recessive individuals show the recessive trait.

Flashcard 9: What is a locus?

Answer: A gene's specific physical location on a chromosome. Each gene occupies a specific position on its chromosome.

Flashcard 10: What is an autosome?

Answer: Any chromosome that is not a sex chromosome. Non-sex chromosomes that follow standard Mendelian inheritance patterns.

Flashcard 11: What is a sex-linked trait?

Answer: A trait controlled by a gene located on a sex chromosome. Inheritance patterns differ from autosomal traits due to sex chromosomes.

Flashcard 12: Which human blood group system demonstrates multiple alleles and codominance?

Answer: ABO blood group. Classic example with three alleles showing both dominance patterns.

Flashcard 13: What is an allele?

Answer: An alternative version of a gene at the same locus. Different forms of the same gene, like $A$ and $a$.

Flashcard 14: What is a carrier in autosomal recessive inheritance?

Answer: A heterozygote with the recessive allele but no disease phenotype. Has one recessive allele but shows the dominant phenotype.

Flashcard 15: State the formula for number of gamete types from a genotype with $n$ heterozygous loci.

Answer: $2^n$. Where $n$ is the number of heterozygous gene pairs.

Flashcard 16: What is multiple alleles inheritance?

Answer: A gene has more than two alleles in the population. Population contains additional allelic variants beyond two.

Flashcard 17: What process can separate linked alleles and create recombinant gametes?

Answer: Crossing over during meiosis. Recombination frequency depends on physical distance between linked genes.

Flashcard 18: What fraction of offspring are expected to be heterozygous in $Aa \times Aa$?

Answer: $\frac{1}{2}$. Half the offspring inherit one allele from each parent.

Flashcard 19: In X-linked inheritance, which parent passes an X chromosome to all daughters?

Answer: The father. All daughters inherit father's X and one maternal X chromosome.

Flashcard 20: What are the possible genotypes for blood type A in the ABO system?

Answer: $I^AI^A$ or $I^Ai$. Type A can be homozygous or heterozygous with $i$ allele.

Flashcard 21: What is a phenotype?

Answer: The observable trait produced by genotype and environment. The physical expression of genes influenced by environmental factors.

Flashcard 22: What is codominance?

Answer: Both alleles are fully expressed in the heterozygote. Both traits appear simultaneously without blending.

Flashcard 23: Identify the required genotype for a recessive phenotype to be expressed.

Answer: Homozygous recessive (two recessive alleles). Recessive traits need both alleles to be recessive for expression.

Flashcard 24: What is a test cross used to determine?

Answer: Whether a dominant-phenotype individual is homozygous or heterozygous. Cross with homozygous recessive reveals the unknown genotype.

Flashcard 25: What genotype produces blood type AB in the ABO system?

Answer: $I^AI^B$. Codominance allows both A and B antigens to be expressed.

Flashcard 26: What is the expected phenotypic ratio from $Aa \times Aa$ with complete dominance?

Answer: $3:1$ (dominant:recessive). Classic ratio when dominant allele masks recessive in heterozygotes.

Flashcard 27: What is a gene in the context of inheritance of traits?

Answer: A DNA segment that encodes a functional product affecting traits. The unit of heredity that codes for proteins or RNA molecules.

Flashcard 28: Which term describes a cross involving one gene with two alleles?

Answer: Monohybrid cross. Focuses on inheritance of a single trait.

Flashcard 29: What is a Punnett square used to predict?

Answer: Expected offspring genotype and phenotype probabilities. A grid showing all possible offspring combinations from a cross.

Flashcard 30: Which human blood group system demonstrates multiple alleles and codominance?

Answer: ABO blood group. Classic example with three alleles showing both dominance patterns.

Flashcard 31: What is a carrier in autosomal recessive inheritance?

Answer: A heterozygote with the recessive allele but no disease phenotype. Has one recessive allele but shows the dominant phenotype.

Flashcard 32: What does it mean if an organism is heterozygous for a gene?

Answer: It has two different alleles at that locus. The alleles differ, written as $Aa$ or $Bb$.

Flashcard 33: What is epistasis?

Answer: One gene masks or modifies the expression of another gene. Gene interactions where one gene affects another's expression.

Flashcard 34: What is the expected phenotypic ratio from $AaBb \times AaBb$ with independent assortment?

Answer: $9:3:3:1$. Classic ratio for two independent traits with complete dominance.

Flashcard 35: What fraction of offspring are expected to be homozygous recessive in $Aa \times Aa$?

Answer: $\frac{1}{4}$. Only one-fourth inherit both recessive alleles.

Flashcard 36: What is a Punnett square used to predict?

Answer: Expected offspring genotype and phenotype probabilities. A grid showing all possible offspring combinations from a cross.

Flashcard 37: What is epistasis?

Answer: One gene masks or modifies the expression of another gene. Gene interactions where one gene affects another's expression.

Flashcard 38: What is a gene in the context of inheritance of traits?

Answer: A DNA segment that encodes a functional product affecting traits. The unit of heredity that codes for proteins or RNA molecules.

Flashcard 39: In a test cross, all offspring show dominant phenotype; what is the parent genotype?

Answer: Homozygous dominant. Uniform dominant offspring indicate parent lacks recessive alleles.

Flashcard 40: What is incomplete dominance?

Answer: Heterozygote shows an intermediate phenotype. Neither allele is completely dominant over the other.

Flashcard 41: Identify the genotype of the tester parent in a standard Mendelian test cross.

Answer: Homozygous recessive. The known genotype that reveals the unknown parent's genetics.

Flashcard 42: What is a sex-linked trait?

Answer: A trait controlled by a gene located on a sex chromosome. Inheritance patterns differ from autosomal traits due to sex chromosomes.

Flashcard 43: What fraction of offspring are expected to show the dominant phenotype in $Aa \times Aa$?

Answer: $\frac{3}{4}$. Includes both homozygous and heterozygous dominant genotypes.

Flashcard 44: What is multiple alleles inheritance?

Answer: A gene has more than two alleles in the population. Population contains additional allelic variants beyond two.

Flashcard 45: What is the expected genotypic ratio from $Aa \times Aa$?

Answer: $1:2:1$ ($AA:Aa:aa$). Shows the actual allele combinations in offspring.

Flashcard 46: What is a genotype?

Answer: The allele combination an organism has for a gene. The genetic makeup, typically written as letter combinations like $AA$ or $Aa$.

Flashcard 47: In a test cross, dominant phenotype parent yields $1:1$ phenotypes; what is its genotype?

Answer: Heterozygous. Mixed offspring ratios indicate the parent has both allele types.

Flashcard 48: What is the expected phenotypic ratio in incomplete dominance for $Aa \times Aa$?

Answer: $1:2:1$. Each phenotype is distinct, including the intermediate form.

Flashcard 49: What is the expected phenotypic ratio in incomplete dominance for $Aa \times Aa$?

Answer: $1:2:1$. Each phenotype is distinct, including the intermediate form.

Flashcard 50: What is a polygenic trait?

Answer: A trait influenced by multiple genes, often with continuous variation. Multiple genes contribute additive effects to phenotype expression.

Flashcard 51: What genotype produces blood type O in the ABO system?

Answer: $ii$. Homozygous recessive produces no A or B antigens.

Flashcard 52: What process can separate linked alleles and create recombinant gametes?

Answer: Crossing over during meiosis. Recombination frequency depends on physical distance between linked genes.

Flashcard 53: What genotype produces blood type AB in the ABO system?

Answer: $I^AI^B$. Codominance allows both A and B antigens to be expressed.

Flashcard 54: How many different gamete types can $AaBb$ produce by independent assortment?

Answer: $4$. Each heterozygous gene contributes two possible alleles to gametes.

Flashcard 55: What is a Y-linked (holandric) trait?

Answer: A trait controlled by a gene on the Y chromosome, passed father to son. Exclusively paternal inheritance through the male lineage only.

Flashcard 56: In X-linked inheritance, which parent always passes an X chromosome to sons?

Answer: The mother. Fathers pass Y chromosomes to sons, X chromosomes come from mothers.

Flashcard 57: What is incomplete dominance?

Answer: Heterozygote shows an intermediate phenotype. Neither allele is completely dominant over the other.

Flashcard 58: How many different gamete types can $AaBbCc$ produce (assume independent assortment)?

Answer: $8$. Three heterozygous genes: $2^3 = 8$ different combinations.

Flashcard 59: What is the expected genotypic ratio from $Aa \times Aa$?

Answer: $1:2:1$ ($AA:Aa:aa$). Shows the actual allele combinations in offspring.

Flashcard 60: What fraction of offspring are expected to be homozygous recessive in $Aa \times Aa$?

Answer: $\frac{1}{4}$. Only one-fourth inherit both recessive alleles.

Flashcard 61: What is a phenotype?

Answer: The observable trait produced by genotype and environment. The physical expression of genes influenced by environmental factors.

Flashcard 62: How many different gamete types can $AaBb$ produce by independent assortment?

Answer: $4$. Each heterozygous gene contributes two possible alleles to gametes.

Flashcard 63: In a test cross, dominant phenotype parent yields $1:1$ phenotypes; what is its genotype?

Answer: Heterozygous. Mixed offspring ratios indicate the parent has both allele types.

Flashcard 64: Which sex chromosome carries most human sex-linked genes?

Answer: The X chromosome. Contains more genes than the smaller Y chromosome.

Flashcard 65: What is Mendel's law of independent assortment?

Answer: Alleles of different genes assort independently in gametes. Different traits are inherited separately if genes aren't linked.

Flashcard 66: What fraction of offspring are expected to show the recessive phenotype in $Aa \times Aa$?

Answer: $\frac{1}{4}$. Only homozygous recessive individuals show the recessive trait.

Flashcard 67: What does it mean if an organism is heterozygous for a gene?

Answer: It has two different alleles at that locus. The alleles differ, written as $Aa$ or $Bb$.

Flashcard 68: Why are X-linked recessive traits more common in males than females?

Answer: Males have one X chromosome, so one recessive allele is expressed. No second X chromosome to mask recessive alleles in males.

Flashcard 69: State the formula for number of gamete types from a genotype with $n$ heterozygous loci.

Answer: $2^n$. Where $n$ is the number of heterozygous gene pairs.

Flashcard 70: What is an autosomal recessive inheritance pattern typically characterized by in pedigrees?

Answer: Trait can skip generations; affected individuals may have unaffected parents. Recessive traits often appear to skip generations in pedigrees.

Flashcard 71: What is linked inheritance?

Answer: Genes close together on the same chromosome tend to be inherited together. Physical proximity reduces crossing over frequency between genes.

Flashcard 72: What is linked inheritance?

Answer: Genes close together on the same chromosome tend to be inherited together. Physical proximity reduces crossing over frequency between genes.

Flashcard 73: What is an autosomal dominant inheritance pattern typically characterized by in pedigrees?

Answer: Trait appears in every generation; affected individuals often have an affected parent. Dominant traits typically show vertical transmission through generations.

Flashcard 74: What is Mendel's law of segregation?

Answer: Allele pairs separate during gamete formation. Each gamete gets only one allele from each pair.

Flashcard 75: In a test cross, all offspring show dominant phenotype; what is the parent genotype?

Answer: Homozygous dominant. Uniform dominant offspring indicate parent lacks recessive alleles.

Flashcard 76: How many different gamete types can $AaBbCc$ produce (assume independent assortment)?

Answer: $8$. Three heterozygous genes: $2^3 = 8$ different combinations.

Flashcard 77: What is a recessive allele in simple Mendelian inheritance?

Answer: An allele expressed only when homozygous. Usually written in lowercase and requires two copies for expression.

Flashcard 78: What is a test cross used to determine?

Answer: Whether a dominant-phenotype individual is homozygous or heterozygous. Cross with homozygous recessive reveals the unknown genotype.

Flashcard 79: What is Mendel's law of segregation?

Answer: Allele pairs separate during gamete formation. Each gamete gets only one allele from each pair.

Flashcard 80: Identify the required genotype for a recessive phenotype to be expressed.

Answer: Homozygous recessive (two recessive alleles). Recessive traits need both alleles to be recessive for expression.

Flashcard 81: What is a dominant allele in simple Mendelian inheritance?

Answer: An allele expressed in the heterozygous phenotype. Usually written in uppercase and masks recessive alleles.

Flashcard 82: What is a locus?

Answer: A gene's specific physical location on a chromosome. Each gene occupies a specific position on its chromosome.

Flashcard 83: What does it mean if an organism is homozygous for a gene?

Answer: It has two identical alleles at that locus. Both alleles are the same, either $AA$ or $aa$.

Flashcard 84: What is Mendel's law of independent assortment?

Answer: Alleles of different genes assort independently in gametes. Different traits are inherited separately if genes aren't linked.

Flashcard 85: What is a polygenic trait?

Answer: A trait influenced by multiple genes, often with continuous variation. Multiple genes contribute additive effects to phenotype expression.

Flashcard 86: What is codominance?

Answer: Both alleles are fully expressed in the heterozygote. Both traits appear simultaneously without blending.

Flashcard 87: What fraction of offspring are expected to show the dominant phenotype in $Aa \times Aa$?

Answer: $\frac{3}{4}$. Includes both homozygous and heterozygous dominant genotypes.

Flashcard 88: What is an allele?

Answer: An alternative version of a gene at the same locus. Different forms of the same gene, like $A$ and $a$.

Flashcard 89: What is pleiotropy?

Answer: One gene affects multiple distinct phenotypic traits. Single genes can influence seemingly unrelated characteristics.

Flashcard 90: What is a genotype?

Answer: The allele combination an organism has for a gene. The genetic makeup, typically written as letter combinations like $AA$ or $Aa$.

Flashcard 91: What genotype produces blood type O in the ABO system?

Answer: $ii$. Homozygous recessive produces no A or B antigens.

Flashcard 92: Which term describes a cross involving two different genes?

Answer: Dihybrid cross. Examines inheritance patterns of two separate traits simultaneously.

Flashcard 93: What is a recessive allele in simple Mendelian inheritance?

Answer: An allele expressed only when homozygous. Usually written in lowercase and requires two copies for expression.

Flashcard 94: What is the expected phenotypic ratio from $Aa \times Aa$ with complete dominance?

Answer: $3:1$ (dominant:recessive). Classic ratio when dominant allele masks recessive in heterozygotes.

Flashcard 95: Which term describes a cross involving two different genes?

Answer: Dihybrid cross. Examines inheritance patterns of two separate traits simultaneously.

Flashcard 96: What does it mean if an organism is homozygous for a gene?

Answer: It has two identical alleles at that locus. Both alleles are the same, either $AA$ or $aa$.