Name: ______________________________
Date: ____________ Period: _____
1. a) What are the two sex chromosomes? _____ and _____
b) Which of these chromosomes is larger than the
other? ______
c) Sex linked traits are found only on the _______
chromosome.
d) Since males only have one X chromosome they only need
to have ________ recessive allele to be affected by it.
2. Cross a carrier (heterozygous) woman with normal vision
with a colorblind man. XBXb x XbY
Legend
XBXB- normal girl
XBXb- normal (carrier) girl
XbXb- colorblind girl
XBY- normal boy
Parents
B
Cross it
Genotype
Phenotype
1 Carrier girl
b
X X
1 Colorblind girl
x
1 Normal Boy
XbY
1 Colorblind boy
XbY- colorblind boy
3. Bill and Bertha want to know if they have a chance at passing on colorblindness to
their kids. Bill and Bertha are not colorblind. However, Bertha’s father was colorblind
(she’s a carrier).
Legend
Parents
Cross it
Genotype
Phenotype
XBXB XBXb XbXb XBY XbY -
Mr. Vorstadt
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4. Hemophilia is a sex-linked trait. Sylvia knows that she is a carrier for the disease and
that her husband is normal.
Legend
Parents
Cross it
Genotype
Phenotype
XHXh
x
XHY
5. Male pattern baldness is another recessive sex-linked trait. Wilbur’s Mother is bald,
and his father isn’t. Cross Wilbur with a woman who is a carrier for baldness.
Legend
Parents
Cross it
Genotype
Phenotype
XMXM- normal girl
XMXm- normal (carrier) girl
-bald girl
XMYXmY-
Mr. Vorstadt
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Pedigrees
A pedigree is a way of indicating generations of mating by using standard symbols.
1. XN = Normal Xn = red-green colorblindness (shaded in)
Using the above key, give the genotype and phenotype of each individual.
1. _____ ___________________
8. _____ ___________________
2. _____
___________________
9. _____
___________________
3. _____
___________________
10. _____
__________________
4. _____
___________________
11. _____
__________________
5. _____
___________________
12. _____
__________________
6. _____
___________________
13. _____
__________________
7. _____
___________________
14. _____
__________________
Mr. Vorstadt
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In fruit flies, eye color is a sex-liked/X-linked trait. Red is dominant to white.
1. What are the sexes and eye colors of flies with the following genotypes:
XRXr _________________
XRY _________________
XRXR _________________
XrY _________________
2. What are the genotypes of these flies:
White-eyed, male __________
White-eyed, female __________
Red-eyed female (Carrier) _________
Red-eyed male __________
3. Show the cross of a white-eyed female XrXr and a red-eyed male XRY.
How many are:
White-eyed, males ______
White-eyed, females __ 0__
Red-eyed, males __0__
Red-eyed, females______
4. Show a cross between a pure red-female and a white-eyed male
What are the genotypes of the parents: ______ & ______
How many are:
White-eyed, males ______
White-eyed, females______
Red-eyed, males______
Red-eyed, females______
5. Show the cross of a red-eyed female (carrier) and a red-eyed male. What is the
genotype of the parents: ______ & ______
How many are:
White-eyed, males ______
White-eyed, females______
Red-eyed, males______
Red-eyed, females______
Mr. Vorstadt
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