1Identify which of the following statements is TRUE: A. In a pedigree all the fa

Question

1Identify which of the following statements is TRUE:

A. In a pedigree all the family members represented are taken from a specific generation.

B. Only one dominant allele for a trait can be expressed in an individual.

C. The phenotypic and genotypic ratios differ for dominant traits but are the same for traits showing incomplete dominance.

D. Heterozygotes and dominant homozygotes always have the same phenotype.

E. There are four common alleles of the gene that controls human blood type.

2Identify which of the following statements is FALSE:

A. Recessive traits are expressed only in the homozygous state.

B. Dominant traits are expressed only in the heterozygous state.

C. The birth order of children in a family is indicated in pedigrees.

D.If each phenotypically normal parent is heterozygous for albinism and deafness, the chance that they will produce a deaf albino is 1 in 16.

E. Pedigree analysis is a reconstruction of a family history.

3Analyze the information in the pedigree in the Fig 1 and determine whether the trait is inherited as:

A Autosomal dominant

B Autosomal recessive

C X-linked dominant

D X-linked recessive

E Y-linked

Analyze the information in the pedigree in the Fig 2 and determine whether the trait is inherited as:

A Autosomal dominant

B Autosomal recessive

C X-linked dominant

D X-linked recessive

E Y-linked

Analyze the information in the pedigree in the Fig 3 and determine whether the trait is inherited as:

A Autosomal dominant

B Autosomal recessive

C X-linked dominant

D X-linked recessive

E Y-linked

Explanation / Answer

1.Ans. C. The phenotypic and genotypic ratios differ for dominant traits but are the same for traits showing incomplete dominance.

The phenotypic and genotypic ratios differ for dominant traits. for example

Tt × Tt

TT

Tall plant

Tt

Tall plant

Tt

Tall plant

tt

short

Phenotypic Ratio - 3 : 1

Genotypic Ratio - 1 : 2 : 1

Incomplete dominance it is the condition where one allele which represents for specific trait is not completely expressed in a pair of alleles and produce new trait, which shows the both penotypic and genotypic ratio is same.

Tt × Tt

TT

Tall plant

Tt

Medium plant

Tt

Medium plant

tt

short

Phenotypic Ratio - 1 : 2 : 1 (Tall : Medium : short)

Genotypic Ratio - 1 : 2 : 1 (TT : Tt : tt)

2.Ans.Dominant traits are expressed only in the heterozygous state.

Dominant trait are expressed in both Homozygous (TT) and Heterozygous (Tt) state

3.Ans.A Autosomal dominant

in X-linked traits the disease never passed from Father to Son. so both the X-linked traits are eliminated from options because in the pedigree trait passed from father to son. and in the pedigree the trait passed from Father to daughter also. so it is not Y-linked. because if it is Y-linked it is not passed from father to daughter.

in the pedigree the trait appears in every generation, this never happens in Recessive traits. so the Answer is Autosomal Dominant.

4.Ans.D X-linked recessive

in X-linked recessive traits more males are effected than females.because males have only one X-chromosome, and females are act as carriers.if effected female marries with a normal man, all their sons are effected and all their daughter are act as carrier who carries trait to next generation.

5.Ans.B Autosomal recessive

TT

Tall plant

Tt

Tall plant

Tt

Tall plant

tt

short

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