Consider the following diploid cell, in which 2n = 8. The blue chromosomes carry

Question

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 only acrocentric and metacentric chromosomes.

Which gene(s) is/are found on the p arm of an acrocentric chromosome? (my answer A C)

A.B.C.D

Which gene(s) is/are found on a metacentric chromosome? (B.D)

A.B.C.D

If this cell undergoes meiosis, how many tetrads will form during prophase I? 4

Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have the genotype ABCD? 1/16

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?

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?

Explanation / Answer

Q1). Which gene(s) is/are found on the p arm of an acrocentric chromosome?

Answer: Gene "C"

p arm mean short arm of the chromosome. The gens A & C are present on the acrocentric chromosomes. The gene "C" is present on the p arm of the chromosome

Q2). Which gene(s) is/are found on a metacentric chromosome?

Answer: B, D

Metacentric chromosome is which has two eual arms. Gene B & D present on metacentric chromosomes

Q3). If this cell undergoes meiosis, how many tetrads will form during prophase I?

Answer: 4 tretrads will be formed

In prophase 1, one maternal and one paternal chromosome of that kind (homologous) lie parellel to each other which is called synapses.

Q4). Given a population of cells like this one that undergo meiosis, what fraction of the gametes produced will have the genotype ABCD? 1/16

Answer: 1/16

The cell contains genes as AaBbCcDd. Total gamets produced are 2n (n=no. of genes). Means 24 =16 types of total gamets.

Aa- possibility of "A" gamet is 50% (1/2)

Bb- possibility of "B" gamet is 50% (1/2)

Cc- possibility of "C" gamet is 50% (1/2)

Dd- possibility of "D" gamet is 50% (1/2)

ABCD gamets probability= 1/2 * 1/2 * 1/2 * 1/2= 1/16

Q5). 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?

Answer: 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

Q6). 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?

Answer:

All dominant (capital letters) genes are present on maternal chromosomes and recessive (small letters) genes are present on paternal chromosome.

The gamets contain only maternal chromosomes (ABCD) is 1/16 (see the answer in Q. NO. 4)

The gamets contain only paternal chromosomes (abcd) is also 1/16

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.