Question

1. Which of the following meiotic process explains the formation of recombinant offspring?

Group of answer choices

The chromosome number is reduced from 2n to 1n.

Sister chromatids are separated during meiosis II.

Homologous chromosomes are separated during meiosis I.

Crossing over of homologous chromosomes during meiosis I.

2.Which of the following does not affect the normal function, structure or number of chromosomes?

Group of answer choices

crossing over during meiosis I.

segment deletion.

non-disjunction during meiosis.

segment translocation between non-homologous chromosomes.

3.Sofia has an inherited form of deafness, although her parents have normal hearing. Deafness is autosomal recessive associated with allele d. The allele for normal hearing, is D. Sofia’s parents have which genotypes?

Group of answer choices

Dd and Dd

DD and dd

DD and dD

dd and dd

Answer 1

1. Crossing over is a reciprocal exchange of equal and corresponding segment between non-sister chromatids in a pair of homologous chromosome. So, this process leads to the recombination of genes present of the two homologous chromosomes which results in the formation of recombinant offspring. Rest of the process mentioned in the other options does not explain the reason for the formation of recombinant offspring.

Option 4 is correct.

1. Crossing over during meiosis-I means the genetic exchange of the genes present on the homologous chromosome of two non-sister chromatids, it does not affect the normal function, structure or number of chromosomes.

But the deletion of any segment will make the chromosome abnormal because a deletion can alter the normal function of the chromosome.

Non-disjunction is a process in which sister chromatids and homologous chromosome fail to separate properly during mitosis or meiosis. So, the number of chromosomes in the daughter cell will differ from the normal condition.

Segment translocation between non-homologous chromosomes alter the genetic sequence of the chromosome, so it will affect the normal function of the chromosomes.

So, it is evident that the, only crossing over during meiosis-I does not affect the normal function, structure or number of chromosomes.

1. The answer is Dd and Dd. The reason for the answer is, Sofia has an inherited disease which is autosomal recessive, so the genotype of Sofia for this disease must be dd. And it is also said that her parents are normal. So, to inherit the disease, her parents must be heterozygotes for the diseased allele.

From the other three options, it is not possible to inherit the recessive alleles to become diseased having the normal phenotype of her parents.

.