FAQs: Genetic Variation

Biology of Women - Dr. Susan Sadler

Vocabulary check: allele, homozygous, heterozygous.

We all carry at least two copies (alleles) of autosomal genes. Why is this so?

Compare and contrast the possible genotypes behind a trait that displays dominant/recessive inheritance patterns.

Imagine that curly hair is a recessive trait that is carried by the "h" gene. Straight hair is coded by the dominant "H" gene. Deb has curly hair. She is planning a family with Dave, who has straight hair. Deb's mother-in-law (Dave's mother) has curly hair.

• What is Deb's genotype for hair texture?

• What is Dave's genotype for hair texture?

• Use matrix analysis to determine the probability that their children will have curly hair.

Not all traits show dominant/recessive inheritance. What is incomplete dominance? What is co-dominance?

When genes coding for traits are located on the same chromosome and are closely linked, what inheritance pattern do you expect? Why?

Crossing over and recombination increase the range of variation in genotype and phenotype. Use recombination to explain a "normal" XX male.

If a trait is sex-linked, on which chromosome is the gene(s) carried? How do the terms: homozygous, heterozygous, and hemizygous apply to analysis of sex-linked genes?

Jean's father was a hemophiliac. Recall that hemophilia is a sex-linked trait. What risk do her children have of suffering from hemophilia if she and her spouse, Jack, have children? Jack is a hemophiliac. (Use matrix analysis again.)

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