1) Find the false statement about the sickle-cell anemia allele. a) changing one

Question

1) Find the false statement about the sickle-cell anemia allele.

a) changing one base-pair of a gene can lead to disease

b) the sickle-cell anemia allele encodes a hemoglobin B protein that is not folded properly

c) sickle-cell anemia is a dominant disease

d) heterozygotes for sickle cell anemia are resistant to infection by the blood parasite that causes

malaria

e) Sickle cell anemia is a serious disease

f) The sickle-cell anemia allele is pleiotropic

2) Find the false statement.

a) Individuals with Down syndrome have 47 chromosomes

b) Individuals with Down syndrome are trisomic for chromosome 21

c) Missing an autosomal chromosome (monosomy) or carrying an extra-autosomol chromosome

(trisomy) is rarely lethal

d) Meiotic non-disjunction can cause trisomy or monosomy

e) The chance of non-disjunction during meiosis starts to increase significantly for women as they

get past 35 years old

f) Dosage compensation ensures that XX females express similar levels of proteins from X-linked

genes as XY males.

3-4-5-6) Consider a human gene for red-green colorblindness located on the X chromosome.

The recessive allele for colorblindness is Xr, while the dominant allele for normal color perception is XR. The Y chromosome does not carry gene R. A man and a woman, both with normal vision, have a colorblind son.

i) Determine the genotype of the mother, father and son.

ii) Draw a Punnett square of the possible genotypes that their next child may have

iii) If their next child is a son, what is the chance that he will be color-blind ? _________

iv) If their next child is a daughter, what is the chance that she will be color-blind ? _____

v) A XRXR mother and a XrY (color blind) father come to you asking for advice. They want to

know their odds are of having a child that is color blind. ____________________________

Explanation / Answer

1. c

2. e

3.

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