Question

In: Biology

A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal...

A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind and of normal height? Justify your answer.

Expert Solution

Achondroplastic dwarfism is an autosomal dominant disease in which a person with homozygous dominant genotype results in lethal phenotype, heterozygous genotype results in achondroplastic dwarf and homozygous recessive genotype expresses normal height. In achondroplastic dwarfism, the development and growth of bones are interfered with by the alleles.

Colour blindness is a sex-linked recessive trait. The gene that is responsible for this disease is located on the X chromosome. It mostly affects males as compared to females. in the case of females, there are two X chromosomes whereas males have only one. So if one of the X chromosomes of a female carries an allele for colorblindness, instead of expressing the colorblind phenotype the woman becomes a carrier.

The genotype of the man who is an achondroplastic dwarf with normal vision will be DdXY

The genotype of the woman who is colorblind with normal height will be: ddXcXc

The offspring produced by these can be represented with the help of a dihybrid cross two show the independent assortment of the two unlinked genes.

Parents: DdXY (♂) × ddXc Xc (♀)

Gametes: DX, DY, dX, dY × dXc

F1 generation:

♂/♀ gametes

DX

DY

dX

dY

dXc

DdXcX

An achondroplastic dwarf daughter who is a carrier for color blindness

DdXcY

Achondroplastic dwarf son with color blindness

ddXcX

colorblind carrier daughter with normal height

ddXcY

colorblind son with normal height

Hence, we can conclude from the above cross that there will be no daughter with colorblindness though there are 50% chances for them to be of normal height or dwarf. So, a daughter with both colorblindness and normal height can not be produced by the given parents.

Answer: none

gladiator answered 2 years ago

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