Non-Mendelian Genetics - AP Biology

1. How does a polygenic inheritance pattern differ from Mendelian?

   Polygenic involves multiple genes contributing to one trait. Creates continuous variation instead of discrete phenotypic classes.

2. Define expressivity in genetic terms.

   The degree to which a genotype is expressed in an individual. Same genotype can produce varying degrees of phenotypic expression.

3. What is a sex-influenced trait?

   A trait that is more common in one sex due to hormonal differences, despite being autosomal. Hormonal differences affect gene expression between sexes.

4. What is the pattern of inheritance for Duchenne muscular dystrophy?

   X-linked recessive. Primarily affects males due to X-linked location.

5. What does pleiotropy refer to in genetics?

   A single gene influences multiple phenotypic traits. Results from the gene product affecting multiple biological pathways.

6. What is the significance of a linkage map?

   Shows the relative position of genes on a chromosome. Distance between genes correlates with recombination frequency.

7. What is an example of pleiotropy?

   The sickle cell gene affects both red blood cell shape and malaria resistance. One mutation affects multiple organ systems simultaneously.

8. Identify a human trait determined by multiple alleles.

   Human ABO blood group system. Three alleles ($I^A$, $I^B$, i) determine four blood types.

9. Identify the inheritance pattern: male-pattern baldness.

   Sex-influenced. Expression depends on sex hormones affecting gene regulation.

10. Determine the phenotype ratio of a monohybrid cross with incomplete dominance.

    1:2:1. No masking of recessive phenotypes occurs in heterozygotes.

11. For X-linked recessive hemophilia, what is the probability that a son of a heterozygous carrier mother will have hemophilia?

    $50\%$. Each son receives his Y chromosome from his father and one of his mother's two X chromosomes, so each son independently has a $50\%$ chance of inheriting her affected X and having hemophilia.

12. Identify an example of a polygenic trait in humans.

    Skin color, which is influenced by multiple genes. Shows continuous variation due to multiple contributing genes.

13. What is a quantitative trait?

    A trait that is measured on a continuous scale and is usually polygenic. Shows bell curve distribution in populations.

14. Define the term 'lethal allele'.

    An allele that causes death in the organism, usually before reproduction. Prevents organism survival or reproduction capability.

15. What is a polygenic trait?

    A trait controlled by two or more genes. Multiple genes contribute additively to the phenotype.

16. What role does the environment play in phenotypic expression?

    It can modify the expression of genetic traits. Gene-environment interactions influence final phenotypic outcomes.

17. What is the expected phenotype ratio in a cross of heterozygotes with codominance?

    1:2:1. Each genotype produces a distinct, recognizable phenotype.

18. What is an X-linked trait?

    A trait determined by a gene located on the X chromosome. Shows different inheritance patterns in males versus females.

19. Define epistasis.

    One gene affects the expression of another gene located at a different locus. One gene masks or modifies the expression of another gene.

20. What is an example of codominance?

    AB blood type, where both A and B alleles are expressed. A and B antigens are simultaneously expressed on red blood cells.

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