Item 6 Consider the following diploid cell, in which 2n = 8. The blue chromosome

Question

Item 6

Consider the following diploid cell, in which 2n = 8. The blue chromosomes carrying genes A, B, C, and D are maternal in origin, whereas the red chromosomes carrying genes a, b, c and d are paternally derived.

Note: In spite of suspect discrepancies in the drawing, this cell contains onlyacrocentric and metacentric chromosomes.

Part D

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have the genotype ABCD?

Enter your answer as a fraction.

Part E

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have two maternal chromosomes and two paternal chromosomes?

Enter your answer as a fraction.

Part F

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have some chromosomes of both maternal and paternal origin?

Enter your answer as a fraction.

Thanks in advance!!

Explanation / Answer

Part D

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have the genotype ABCD?

if no recombination or crossing over occurred between the genes and the cenriomeres.homologous cheomosomes are paired and aligned on the metaphase plate.

gamets produced will be: A B C D

all of Metarnal origin? 1/16 -- This probability is determined by assuming that any given chromosome has a 1/2 probability of being in any given cell after anaphase I of meiosis. Thus the probability that all of the parental chromosomes would go into the same cell is given by multiplying the probabilities of each individual chromosomes going into that cell. Thus 1/2 X 1/2 X 1/2 X 1/2 = 1/16

Part E

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have two maternal chromosomes and two paternal chromosomes?

half of maternal origin and half of paternal origin? 6/16
There are six ways that this can occur (abCD, aBcD, AbcD, aBCd, AbCd, ABcd). Each occurrence has a probability of 1/16 and the sum of the six probabilities is 6/16.

Part F

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have some chromosomes of both maternal and paternal origin?

There are six ways that this can occur (abCD, aBcD, AbcD, aBCd, AbCd, ABcd). Each occurrence has a probability of 1/16.

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