Mitosis and meiosis questions

Question 1

Why are different alleles within a population important ?

Answer 1

• They introduce genetic variation
• Some combinations can provide an organism with an advantageous characteristic e.g resistance to a disease, longer neck to access food.
• If the environment alters organisms with favourable mutations/allelessurvive
• Natural selection/selection pressure/survival of fittest§

Question 2

Why is meiosis important in organisms which reproduce sexually ?

Answer 2

• Results ingenetically distincthaploid cells
• Ensuresdiploid number of chromosomes is restoredin fertilisation
• Variationgenerated through crossing over and independent assortment
• Allows for agenetically different zygoteto be formed through the fusion of the nuclei of random gametes during random fertilisation.

Question 3

Give fivedifferences between mitosis and meiosis

Answer 3

1. Mitosis has onecell division but meiosis has two
2. Mitosis maintains the original diploid chromosome number whilst meiosis halves chromosome number
3. Mitosis produces two daughter cells whilst meiosis produces four
4. Daughter cells are genetically identical to the parent cell in mitosis but genetically different in meisosis
5. Mitosis produces somatic cells whilst meiosis produces gametes

Question 4

Compare the genetic makeup of daughter cells produced by mitosis with the original parent cell

Answer 4

• Genetically identical
• Have same number of chromosomes
• Have the same genes as the parent cell

Question 5

Why is mitosis important in the life cycle of a human ?

Answer 5

• It allows for the growth of a human
• Repairs tissues
• Genetically identical cells produced
• Throughout life maintain chromosome number

Question 6

Why is mitosis important in the repair of tissues ?

Answer 6

• Cells produced in mitosis are genetically identical
• Allows cells to carry out the same function as the parent cell
• Daughter cells havethe correct information to develop the same type of cell as parent cells

Question 7

What is the difference between sister and non-sister chromatids ?

Answer 7

They have different alleles

Question 8

When does independent assortment occur in meiosis ?

Answer 8

Metaphase I and Metaphase II

Question 9

Why is it important in sexual reproduction that gametes are haploid ?

Answer 9

• Without gametes there is less variation
• Gametes fuse to form a diploid cell
• Prevents doubling number of chromosome number in each successive generation

Question 10

Why does meiosis need to have twice as many stages as mitosis ?

Answer 10

• Gametes must be haploid as when they fuse a diploid cell must form
• To halve the numberchromosomes from 2n to n
• To separate homologous pairs of chromosomes

Question 11

What is the difference between prophase I and prophase II ?

Answer 11

• In prophase Ichromosomes condense to become visible and homologous chromosomes pair up to formbivalents
• In prophase IIthe chromosomes consist of two chromatids that condense to becomevisible again.

Question 12

Why is it important that the genetic information is checked at the checkpoints ?

Answer 12

• Otherwise mutation of a gene could occur
• Which would mean a protein necessary for a particular function might not be produced
• A cell could end up with too many (or little) chromosomes
• Could form a trisomy which can lead to downs syndrome

Question 13

Why is replication of DNA before division of the nucleus in mitosis essential ?

Answer 13

• Cells produced are genetically identical, both daughter cells receive a full copy of the parent cell’s DNA
• Diploid daughter cells are produced
• To maintain the chromosomal number