mitosis past paper questions

Question 1

describe and explain the arrangement of genetic material in prophase?

Answer 1

chromosomes becoming visible as they are condensing

Question 2

describe the role of spindle fibres and the behaviour of chromosomes during prophase, metaphase and anaphase?

Answer 2

-In prophase, chromosomes condense and become visible

-in metaphase, centromeres attach to spindle fibres

-in anaphase, centromeres divide and sister chromatids are pulled to opposite poles of the cell, this is due to the spindle contracting.

Question 3

why did the student only use the first 5mm from the tip of an onion root?

Answer 3

region where root grows so mitosis is occurring here

Question 4

why did the student press down firmly on the cover slip?

Answer 4

spread out cells to get a single layer, so light passes through

Question 5

describe and explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate?

Answer 5

examine large number of fields of view to ensure a representative sample

Question 6

give two pieces of evidence from Figure 1 that suggests this cell was undergoing mitosis?

Answer 6

individual chromosomes are present and visible so they must have condensed during prophase

each chromosome is made of two chromatids because DNA has been replicated

Question 7

what is a homologous pair?

Answer 7

two chromosomes that carry the same genes in the same loci but may have different alleles of those genes

Question 8

describe the appearance and behaviour of chromosomes in mitosis?

Answer 8

PROPHASE
-chromosomes condense and become visible
-chromosomes appear as two sister chromatids joined at the centromere

METAPHASE:
-chromosomes line up at equator of cell
-chromosomes attached to spindle fibres by their centromere

ANAPHASE:
-sister chromatids pulled to opposite poles of the cell

TELOPHASE:
-chromosomes decondense

Question 9

give two reasons why mitosis is important in the life of an organism?

Answer 9

1. Growth- increase in cell number
2. Replace cells-repairing tissues/ organs

Question 10

describe the role of the centromere in mitosis?

Answer 10

-holds chromatids together
-attaches chromatids to the spindle
-allows chromatids to be separated