Question

1. which of the following events characterizes metaphase of mitosis?

           1. attachment of spindle fibers to the kinetochores of the chromosomes

           2. movement of chromosomes to the equatorial plane of the cell.

           3. separation of sister chromatids that are being pulled to the poles of the cell

A. 1

B. 2

C. 3

D. 1 and 2

E. All of these

2. One cell undergoes one round of meiosis. How many genetically identical cells will be present at the end of this one round of meiosis?

A. 2

B. 4

C. 8

D. 0

E. impossible to tell

3. The house fly, musca domestica, has a haploid chromosome number of 6. How many chromatids should be present in a diploid, somatic, metaphase cell?

A. 3

B. 6

C. 12

D. 18

E. 24

4. The following events are common to mitosis and meiosis except for?

A. DNA replication precedes cell division

B. Homologous chromosomes segregate

C. Sister chromatids segregate

D. DNA condenses during cell division

E. Cytokinesis occurs at the end of cell division

Answer 1

Q1. Option D. 1&2

During metaphase stage, all chromosomes arranged in a equatorial plate according to their centromere position. At the same time spindle fibres are attached to the kinetochore of centromere of each chromosome.

Separation of sister chromatids is a characteristic feature of anaphase.

So the right option is D

Q2. Option D. 0

Meiosis produces four daughter cells. All the daughter cells are genetically different from one another because of recombination. During pachytene stage of Prophase crossing over occurs to exchange the genetic material between two non sister chromatids of homologous chromosomes. This leads to the daughter cell become genetically dissimilar.

But in mitosis, formed daughter cells are genetically similar to each other since there is no recombination occurs.

Q3. Option E

Single chromosome at its haploid stage has a single chromatid. After a DNA replication new chromatid is formed called as sister chromatid and both chromatids held together by a centromere. So at its diploid stage, chromosome has two sister chromatids.

In Musca domestica haploid number of chromosomes is 6, it means the number of chromatids present is also 6. In diploid stage one more sister chromatid is added to each chromosome. So each chromosome has two chromatids. In diploid condition chromosome number is 12. Therefore total number of chromatids is 24.

Q4. Option B.

Both in mitosis and meiosis, DNA preceds cell division. Cell division begins only after the completion of replication of DNA occurs. During the formation of chromatids and chromosomes DNA is get condensed. And chromosomes are arranged in an equatorial plate and are get segregated. After this step cytokinesis occurs to form new daughter cells.

In meiosis, homologous chromosomes are get segregated but in mitosis no segregation of homologous chromosomes occurs. In meiosis, segregation of homologous chromosomes occurs at anaphase I of meiosis I. And segregation of sister chromatids occurs at anaphase II of Meiosis II.

In Mitosis, segregation of sister chromatids occurs at anaphase without the segregation of homologous chromosomes.