In the following pedigrees, the disorders or traits presented follow simple patt

Question

In the following pedigrees, the disorders or traits presented follow simple patterns of Mendelian inheritance. For each pedigree, determine the most probable mode of inheritance of the trait, stating whether the trait is due to an autosomal or X-linked gene, and whether it is due to a dominant or recessive allele. Indicate and explain the evidence supporting your choice of pattern, and note evidence that does not support or conclusively eliminates the other patterns. Provide specific examples to defend your statements.

Then, providing a legend for your symbols, assign genotypes to the specified individuals. (BELOW)

Pedigree A

Provide genotypes for individuals I-4, II-2, III-12, and IV-2.

& From

Pedigree B

Provide genotypes for individuals I-2, II-4, III-2, and IV-8.

please oNLY ATTEMPT IF GENETICS IS YOUR SPECIALTY!!

                                            (20 marks)

Explanation / Answer

Pedigree A;

It is an autosomal dominant disorder.

Autosomal dominant traits appear in both sexes with equal frequency, and both sexes are capable of transmitting these traits to their offspring. Every person with a dominant trait must have inherited the allele from at least one parent; autosomal dominant traits therefore do not skip generations.

Genotype of individual,

I-4 = Aa.

I-4 is heterozygous for the triat and has transmitted the mutated allele to one of the offspring (II-7) out of four offsprings. If I-4 would have been homozygote then all his offsprings would have been affected.

II-2 = AA.

( It is normal homozygous for the triat as non of his offsprings are affected).

III-12 = Aa.

It is also heterozygous as her offspring (IV-5) is normal for the triat.

IV-2 = AA.

It is homozygous normal.

Pedigree B:

It is an autosomal recessive triat.

Autosomal recessive traits normally appear with equal frequency in both sexes and appear only when a person inherits two alleles for the trait, one from each parent. If the trait is uncommon, most parents of affected offspring are heterozygous and unaffected.

Genotype of;

I-2 = Aa.

This individual is heterozygous and carries on mutant allele for the triat. We can say this about its genotype as one of its offspring is affected and had received one mutant allele each from one parent.

II-4 = Aa.

It is also heterozygous as one of its offspring (III-9) is affected and would have received one mutant allele each from one parent.

III-2 = Aa.

Same explanation

IV-8= Aa.

It has one affected parent and one normal and had recieved one mutant allele from one parent and one normal allele from other parent.

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