Question

70;The wide variation in skin color in humans is best explained by

Group of answer choices

Skin color is influenced by an X-linked gene.

Skin color is influenced by environmental changes like improvements in diet.

Skin color is influenced by crossing over.

Skin color is a polygenic trait.

Skin color is influenced by a Y-linked gene.

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Question 71

Linked genes, by definition, are genes that

Group of answer choices

have no alleles.

are found in the same species.

are found on the same chromosome.

are alleles that are found in different daughter cells.

have more alleles than usual.

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Question 72

In the ABO blood type system the alleles IA, IB and i produce

Group of answer choices

three phenotypes.

four phenotypes.

one phenotype.

two phenotypes.

type A and type B blood types only.

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Question 73

Phenotype means

Group of answer choices

the number of chromosomes in an individual.

the observable expression of the genes in an individual.

the genes an individual has.

the combination of alleles in an individual.

the number of gametes in an individual.

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Question 74

The most common or "normal" phenotype or allele for a gene in a population is the

Group of answer choices

the recessive population.

the F1 generation.

the P generation.

the wild type.

the dominant population.

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Question 75

If a pea plant is homozygous for yellow seeds (YY), which gametes will it produce?

Group of answer choices

YYyy

Y or y

Yy

y only

Y only

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Question 76

To inherit an autosomal recessive disorder requires the person receive the disease causing allele from

Group of answer choices

only one parent who is homozygous recessive for the disease.

both parents.

only the parent having the disease.

the father only.

the mother only.

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Question 77

If a pea plant is homozygous recessive for yellow seeds (yy), which gametes will it produce?

Group of answer choices

Y only

Yy

YYyy

Y or y

y only

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Question 78

If the two alleles for a particular gene are identical the gene pair is

Group of answer choices

heterozygous.

recessive.

homologous.

homozygous.

dominant.

Answer 1

70. Skin colour is a polygenic trait.

Polygenic traits are those which are controlled by more than one gene. Skin colour is controlled by 3 genes. Each gene is having 2 alleles so there are 6 alleles in total.

Polygenic traits are also called as quantitative traits. And the genes related to the traits are called as quantitative trait loci. These traits of a variable number of phenotypes and a bell shaped curve is obtained if the frequency of each phenotype is plotted. The maximum frequency is that of the intermediate. These traits are affected by environment also and therefore they are also called as multifactorial traits.

71. Found on same chromosome

Linkage is an exception to the law of independent assortment. According to the law of independent assortment, alleles of genes segregate independently of each other during gamete formation so that every gamete receives one allele of a gene.

But in case of linkage, genes do not assort independently of each other because they are located very close to each other on the same chromosome.

If the distance between the two genes is less than 50 map units, then the genes are said to be linked and if it is equal to or more than 50 map units, then the genes show independent assortment.

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