Question

Use the following information as the basis for answering all questions: A diploid eukaryotic organism has 3 unique chromosomes. Chromosome I is a metacentric chromosome, chromosome II is a telocentric chromosome, and Chromosome III is a submetacentric chromosome.

1.)How many total chromosomes do the somatic cells of this organism have in G2 of cell cycle?

2.) How many total chromatids do the somatic cells of this organism have in G2 of cell cycle?

3.) How many total chromosomes are in a germ cell in the ovary of this organism that is in Anaphase of Meiosis I?

.4.) How many total telomeres are in a germ cell in the ovary of this organism that is in Anaphase of Meiosis I?

5.) Viruses are living organisms, because they contain DNA and RNA.        A) TRUE        B) FALSE

6. The field of genetics includes the study of cellular processes including transcription and translation. A) TRUE     B) FALSE

7. Sequencing of organisms’ DNA has in many cases resulted in their original taxonomic reclassification based upon anatomical structure.     A) TRUE       B) FALSE

8. The # of chromosomes per cell never changes at any point during mitotic cell division. A) True                 B) False

Answer 1

A chromosome contains two chromatids, each of which contains a telomeric end at the extremity. Thus, a metacentric and submetacentric chromosome would have 2 chormatids and 4 telomeres whereas a telocentric chromosome would have 2 chromatids but only 2 telomeres. Further, it is important to note here that meiosis I is equational type of cell division where no reduction in chromosome number takes place. The splitting of chromosome from the centromere takes place only in anaphase II of meiosis II following which comes telophase II. The resultant daughter cells after telophase II contains haploid set of chromosomes.

Thus, using this information, the answers can be found as below:

Answer 1: The somatic cells would have a double number of chromosomes since mitotic phase succeeds after G2. Thus, this cell would contain a total of 3*2=6 chromosomes.

Answer 2: Since each chromosome contains 2 chromatids, this cell would contain 6*2=12 chromatids at G2.

Answer 3: At anaphase I, the number of chromosomes are equally distributed in both the cells. Thus, both these daughter cells would contain 3*2=6 chromosomes.

Answer 4: These 6 chromosome would have a total of 2 telocentric chromosomes whereas other two pairs would be metacentric and sub-metacentric. Thus, total number of telomeres would be given by 2*2 +2*2 +2*1 = 10.