Sex-linked traits AP Biology practice questions

🧬 Topic Summary

Sex-linked traits are characteristics that are determined by genes located on the sex chromosomes (X and Y in humans). Because females have two X chromosomes (XX) and males have one X and one Y chromosome (XY), the inheritance patterns of these traits differ between the sexes. Most sex-linked traits are X-linked, meaning the gene responsible for the trait is located on the X chromosome. Males are more likely to express recessive X-linked traits because they only have one X chromosome. If that single X chromosome carries the recessive allele, they will exhibit the trait. Females, on the other hand, must inherit two copies of the recessive allele to express the trait.

Understanding the concepts of dominant and recessive alleles, genotypes, and phenotypes is crucial for solving problems related to sex-linked traits. Punnett squares are often used to predict the probability of offspring inheriting specific traits based on the parental genotypes. Remember to carefully track the X and Y chromosomes when analyzing these problems!

🧪 Part A: Vocabulary

Match the terms with their definitions:

📝 Part B: Fill in the Blanks

In humans, sex-linked traits are typically associated with the _____ chromosome. Males are considered ______ for genes on the X chromosome because they only have one copy. A female will only express a recessive X-linked trait if she inherits _____ copies of the recessive allele. Color blindness is a common example of a(n) ______ trait. Punnett squares are useful tools for predicting the probability of offspring inheriting specific _____.

🤔 Part C: Critical Thinking

A woman who is a carrier for hemophilia (an X-linked recessive disorder) has children with a man who does not have hemophilia. What is the probability that their son will have hemophilia? Explain your reasoning.