Mendelian Genetics - AP Biology

1. What is a dominant allele?

   An allele expressed in heterozygotes. Only one copy needed for phenotypic expression.

2. What is the probability of obtaining a recessive phenotype in a monohybrid cross?

   $\frac{1}{4}$. From F1 × F1 cross, recessive appears in $\frac{1}{4}$ offspring.

3. What is a carrier in genetics?

   An individual heterozygous for a recessive trait. Has recessive allele but doesn't express the trait.

4. Define Mendel's law of independent assortment.

   Genes for different traits assort independently. Inheritance of one trait doesn't affect another trait's inheritance.

5. What is a Punnett square used for?

   Predicting the outcome of a genetic cross. Grid showing all possible gamete combinations from a cross.

6. What is the F2 generation?

   Offspring from interbreeding F1 individuals. Second generation from F1 × F1 cross.

7. What is a heterozygous genotype?

   Two different alleles for a trait. One allele is different from the other (Aa).

8. What is the purpose of a test cross?

   To determine an organism's genotype. Cross with homozygous recessive to reveal unknown genotype.

9. What is the expected genotypic ratio for a cross of heterozygotes?

   1:2:1 for a single trait with complete dominance. Standard F2 genotypic ratio from monohybrid cross.

10. Define genotype.

    Genetic makeup of an organism. The actual alleles present in an organism.

11. What is codominance?

    Both alleles are expressed equally. Neither allele is dominant over the other.

12. What is a monohybrid cross?

    A cross examining one trait. Focuses on inheritance patterns of a single characteristic.

13. What does it mean if an individual is homozygous dominant?

    They have two dominant alleles for a trait. Expresses dominant phenotype for that trait.

14. What is an allele?

    A variant form of a gene. Different versions of the same gene at a locus.

15. What is the phenotypic ratio in a dihybrid cross?

    9:3:3:1 for two independent traits. Classic ratio from F1 × F1 dihybrid cross.

16. Which term describes a gene with multiple alleles?

    Multiple allelism. More than two allelic variants exist for one gene.

17. What does a 1:1:1:1 ratio in offspring suggest?

    Test cross with a heterozygous dihybrid. Equal proportions indicate independent assortment of traits.

18. How does a test cross determine genotype?

    By crossing with a homozygous recessive individual. If recessive offspring appear, original was heterozygous.

19. What is a dihybrid cross?

    A cross examining two traits. Studies inheritance of two different characteristics simultaneously.

20. What is the principle of segregation in Mendelian genetics?

    Alleles separate during gamete formation. Each parent contributes one allele per trait to offspring.

21. What is the genotypic ratio in a monohybrid cross?

    1:2:1 for homozygous dominant, heterozygous, homozygous recessive. Genotype distribution from F1 × F1 monohybrid cross.

22. What is pleiotropy?

    One gene influences multiple traits. Single gene affects multiple, seemingly unrelated characteristics.

23. What is the sum rule in genetics?

    Probability of mutually exclusive events is the sum of their probabilities. Add probabilities for either-or scenarios.

24. What does it mean if an individual is homozygous recessive?

    They have two recessive alleles for a trait. Expresses recessive phenotype for that trait.

25. What is the product rule in genetics?

    Probability of two independent events occurring together is the product of their probabilities. Multiply individual probabilities for combined events.

26. What is the probability of obtaining a dominant phenotype in a monohybrid cross?

    $\frac{3}{4}$. From F1 × F1 cross, dominant appears in $\frac{3}{4}$ offspring.

27. Which organism did Mendel use for his experiments?

    Pea plants (Pisum sativum). Ideal model organism with clear, distinct traits.

28. What does a homozygous genotype consist of?

    Two identical alleles for a trait. Both alleles are the same (AA or aa).

29. Identify the F1 generation.

    The first filial generation from a cross. Immediate offspring from parental cross.

30. Define incomplete dominance.

    Heterozygote shows an intermediate phenotype. Blended phenotype between two homozygous parents.

31. What does a 9:3:3:1 ratio in offspring indicate?

    Dihybrid cross with independent assortment. Classic Mendelian ratio for two independent traits.

32. What is the expected phenotypic ratio for a cross of heterozygotes?

    3:1 for a single trait with complete dominance. Standard F2 phenotypic ratio from monohybrid cross.

33. What is a pedigree chart?

    A diagram showing familial relationships and traits. Traces inheritance patterns through family generations.

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