Question

Primary spermatocytes are diploid (2n) cells with all of the organelles typically found in eukaryotic animal cells. A representation of spermatogenesis from a primary spermatocyte with six chromosomes is shown in Figure 1. 

 

1. Describe the process in meiosis that ensures that both maternal and paternal chromosomes are passed on to each Spermatozoon

2. Explain why the genetic content of individual chromosomes in a spermatozoon most likely differs from the genetic content of individual chromosomes in a primary spermatocyte

3. In some instances, meiosis of a primary spermatocyte with six chromosomes results in two spermatozoa that contain four chromosomes and two spermatozoa that contain two chromosomes. Predict the most likely cause

4. A student claims that if the animal producing the spermatozoa has a mutation in a mitochondrial gene, the probability that any offspring will inherit the mutation is zero. Provide evidence to support this claim

 

Answer 1

1. Every individual contain a diploid set of chromosome a, single pair represent the homologous pairing of chromosome.

One of the homologous pair come from paternal side and other homologous pair come from the maternal side. The separation of chromosome in such a manner that both maternal and paternal chromosomes are passed on to each Spermatozoon is due to crossing over which takes place in pachytene stage of prophase I of meiosis I.

2. The genetic content of individual chromosomes in a spermatozoon most likely differs from the genetic content of individual chromosomes in a primary spermatocyte because in primary spermatocytes meiosis I takes place which segregrate the homologous pairing of chromosome in a diploid organism to form haploid gamete as it can we seen in secondary spermatocyte, spermatids and spermatozoon.

3. This is the case of aneuploidy which occurs due to non- disjunction happens during chromosomal segregation in meiosis which create a spermatozoa with 4 chromosome and another with 2 chromosome resulting in trisomic and monosomic aneuploidy.

4. If the animal producing the spermatozoa has a mutation in a mitochondrial gene, the probability that any offspring will inherit the mutation is zero because sperm carry only genetic material to female gamete during gametic fusion, it doesn't contribute it's other cellular compartment during fusion.