Sex-Linked Traits -in humans, there are 2 chromosomes that determine gender: either X or Y -females have 2 X chromosomes, noted as XX -males have 1 X chromosome and 1 Y chromosome, noted as XY female male

Sex-Linked Traits -X chromosome is bigger than Y chromosomes, so it holds more information -e.x. XRXr vs. XRY

Sex-Linked Traits -Dominant and recessive traits work the same; the only difference is that Y doesn’t hold an allele For example: XRXR = homozygous XRXr = heterozygous XrXr = homozygous XRY = neither

Sex-Linked Traits -some well-known sex-linked traits include: 1. colorblindness (can’t see red or green) 2. hemophilia (excessive bleeding) 3. male pattern baldness (loss of hair) 4. Duchenne muscular dystrophy (muscle degeneration)

Sex-Linked Questions Questions: 1. Look at the Punnett Square below. Keeping in mind that colorblindness is a recessive trait, which of the parents (if any) are colorblind? 2. What is the probability of the offspring (if any) being colorblind? What gender are they? 3. Colorblindness is typically associated with males. Why do you think that is? 4. Based on the possible Punnett Squares that can be made, do you think it is possible for a female to be colorblind? How might that be?