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Sex-linked traits (also called X-linked traits)
Sex-linked traits (also called X-linked traits)
In humans, the 23rd pair of chromosomes determine the sex, or gender, of the offspring.
In humans, the 23rd pair of chromosomes determine the sex, or gender, of the offspring.
'XX' = female (girl)
'XX' = female (girl)
'XY' = male ('Y' is 'guy stuff')
'XY' = male ('Y' is 'guy stuff')
Most sex-linked traits are carried on the 'X' chromosome, not on the 'Y,' so we will focus on x-linked traits.
Most sex-linked traits are carried on the 'X' chromosome, not on the 'Y,' so we will focus on x-linked traits.
XH The capital H represents the dominant allele
XH The capital H represents the dominant allele
Xh The lowercase h represents the recessive allele
Xh The lowercase h represents the recessive allele
Y Y is 'guy stuff' and carries no copy of the allele
Y Y is 'guy stuff' and carries no copy of the allele
XH Xh If there is one capital H and one lowercase h, this is called a carrier female. She is not affected by the recessive trait, but she carries the allele and can pass it to her offspring. It is especially important to track carriers of diseases.
XH Xh If there is one capital H and one lowercase h, this is called a carrier female. She is not affected by the recessive trait, but she carries the allele and can pass it to her offspring. It is especially important to track carriers of diseases.
Complete the page below in your packet, then ask for the answer key to check your work.
Complete the page below in your packet, then ask for the answer key to check your work.
Complete these practice problems on blank paper to make sure that you can set up problems for yourself.
Complete these practice problems on blank paper to make sure that you can set up problems for yourself.
For each problem, write a key, the cross, the Punnett square, and the genotypes and phenotypes of offspring.
For each problem, write a key, the cross, the Punnett square, and the genotypes and phenotypes of offspring.
1. Hemophilia is a sex-linked recessive trait. Cross a carrier female with a male who has the bleeding disorder.
1. Hemophilia is a sex-linked recessive trait. Cross a carrier female with a male who has the bleeding disorder.
2. Male patterned baldness is a sex-linked recessive trait. Cross a normal female with a bald male.
2. Male patterned baldness is a sex-linked recessive trait. Cross a normal female with a bald male.
Bring your problems to me to ensure that you are setting them up correctly.
Bring your problems to me to ensure that you are setting them up correctly.
Ask me for the answer key to check your work in the packet.
Ask me for the answer key to check your work in the packet.
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