Please answer the following 10 questions below about human genetics. Achondropla
ID: 19593 • Letter: P
Question
Please answer the following 10 questions below about human genetics.Achondroplasia (dwarfism) is an autosomal dominant disorder. A dwarf mother and a dwarf father have 4 children. The first 2 are dwarfs, and the last 2 are of normal height.
1) What are the chances of a non-dwarf child from this union?
2) What is the mother’s genotype?
3) What is the father’s genotype?
Color-blindness is a sex-linked recessive disorder. A heterozygous female mates with a male with a colorblind male.
4) What are the chances of this couple having a child who is color-blind?
5) What are the chances of this couple having a girl who is color-blind?
6) What are the chances of this couple having a boy who is color-blind?
The ability to roll your tongue and having freckles are both autosomal dominant traits. A woman who cannot roll her tongue, and is heterozygous for having freckles mates with a man who is homozygous dominant for both traits.
7) What are the chances of this couple having a child who is homozygous dominant for both traits?
8) Heterozygous for both traits?
9) Homozygous recessive for both traits?
10) Heterozygous for one of the 2 traits?
Explanation / Answer
Since the couple produced non dwarf children we know they are not both dominant. They have to heteroyzgous. Let's say they are both Bb
1. Chance of non dwarf are getting a b and b allele from both parents. so 1/2 *1/2 = 1/4
2. Mother's genotype and father's genotype are both Bb, heterozygote. They cant be bb otherwise they wouldn't be dwarfs themselves because the disease is dominant. And they cant be BB otherwise they wouldnt have normal height children.
Let's say r is the gene for colorblindness. R is dominant and r is recessive
4. Female has 1/2 chance of passing it r while male will definitely pass r so 1/2 chance of producing child who is color blind
5. getting a girl is 1/2 chance and getting color blind is also 1/2 so 1/2*1/2 = 1/4
6. Getting a girl is also 1/2 chance and getting color blind is 1/2 so 1/2*1/2 = 1/4
7. 0 because the mother does not have a dominat allele for rolling the tongue because she is recessive for it.
8. Chance of being hetroyzgote for tongue is 1 and chance of being heterozygote for freckles is 1/2*1 = 1/2 . So overall chance is 1/2
9. 0 because the father has no recessive alleles to give.
10. 1 because the father will always pass a dominant tongue allele and the mother will always pass a recessive tongue allele. Thus the tongue will always be heterozygote.