mitosis and meiosis exam qs

Question 1

The student prepared a temporary mount of the onion tissue on a glass slide. She
covered the tissue with a cover slip. She was then given the following instruction.
“Push down hard on the cover slip, but do not push the cover slip sideways.”
Explain why she was given this instruction.

Answer 1

Push hard – spread tissue;
Not push sideways – breaking chromosomes

Question 2

Apart from mutation, explain one other way genetic variation within a species is increased.

Answer 2

Random fertilisation;
2. (Produces) new allele combinations

Question 3

Describe the process of crossing over and explain how it increases genetic diversity.

Answer 3

Homologous pairs of chromosomes form a bivalent;
2. Chiasma(ta) form;
3.alleles are exchanged;
4. Producing new combinations of alleles

Question 4

Explain how the chromosome number is halved during meiosis

Answer 4

Homologous chromosomes (pair);
2. One of each (pair) goes to opposite poles

Question 5

Suggest why the student soaked the root tips in hydrochloric acid in step 2.

Answer 5

To separate cell walls;
2. Allowing the stain to pass

Question 6

Describe how you would determine a reliable mitotic index (MI) from tissue observed
with an optical microscope.

Answer 6

Count cells in mitosis in field of view;
2. Divide this by total number of cells in field of
view;
3. Repeat many times

Question 7

Describe how the process of meiosis results in haploid cells.
Do not include descriptions of how genetic variation is produced in meiosis.

Answer 7

1. DNA replication (during late interphase);
2. Two divisions;
3. Separation of homologous chromosomes (in
   first division);
4. Separation of (sister) chromatids (in second
   division);