Question

1) To determine experimentally if two genes are linked, you would do mating studies and look at the rate of _________.

Select one:

a. mutation

b. nondisjunction

c. crossing over

d. codominance

2) For the results of Mendel's dihybrid cross to be a 9:3:3:1 ratio of traits, what must be true?

Select one or more:

a. The sample size must be sufficiently large.

b. The alleles of the two genes involved must exhibit a simple dominant/recessive relationship.

c. The genes must be linked.

d. The P generation must be homozygous.

e. The genes must be for the same trait.

f. The alleles for one gene must separate independently of the alleles for the other gene.

g. Every possible combination of alleles for every gene is equally likely to occur.

h. The genes must be on the same chromosome.

3) Human males always express the genes on their single X chromosome; thus they are said to be ____Answer_____ for these traits.

Thank you for your help. It is greatly appreciated :)

Answer 1

1) Crossing over is the right option.

We have to check that what is the crossing over or recombination frequency between two genes. If it is less than 50% then genes are said to be linked other wise not.

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2)

Following are the right statements:

*A) the sample size must be large because when sample size is small then there will be less chances of proper fusion between gametes and deviates this ration.

*B) The allele to two genes must exhibit simple dominant receive relationship.

*e) the genes must be for same trait.  

*f) the allele for one gene must separate independently of the allele for other gene.

*g) every possible combination of allele for every gene is equally likely to occur

Why other option wrong:

*c) if genes are linked, then gametes are not found in equal number. In this case parental gametes type are more as compared to recombinant and deviated this ration.

*d) The P generation must be heterozygous.

*h) two genes are either unlike when found on same chromosome or found on different chromosome.

3)  

Hemizygous is the answer. Because the phenotype is determined only because of presence of one X linked chromosome.