Biology Flashcards: Relate Genes To Trait Inheritance

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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.

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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: 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 2: 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 3: How many different gamete types can $AaBb$ produce by independent assortment?

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

Flashcard 4: 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 5: How many different gamete types can $AaBbCc$ produce (assume independent assortment)?

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

Flashcard 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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 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 locus?

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

Flashcard 15: 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 16: What is a phenotype?

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

Flashcard 17: 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 18: 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 19: 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 20: 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 21: What is Mendel’s law of segregation?

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

Flashcard 22: 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 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 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 25: 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 26: Which term describes a cross involving one gene with two alleles?

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

Flashcard 27: Which term describes a cross involving two different genes?

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

Flashcard 28: 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 29: 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 30: 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.