Mitosis

Question 1

Interphase

Answer 1

• growth phase - protein synthesis, cytoplasm
• DNA replicates
• protein necessary for cell division are synthesised

Question 2

Why do cells need to divide by mitosis?

Answer 2

• asexual reproduction
• growth by producing more cells
• repair of damaged tissue
• replace old or worn out cells

Question 3

Chromatin

Answer 3

DNA chromosomes are unwound and structures are not visible

Question 4

Prophase

Answer 4

-Chromosomes coil-up & condense
-nuclear envelope disappears
-nucleolus disappears
-centrioles move to opposite side of the nucleus
-spindle fibres form

Question 5

Metaphase

Answer 5

-Chromosomes arrange themselves on the equator of the spindle
-microtubules attached to the centromere

Question 6

Anaphase

Answer 6

-centromeres divide in 2
-attached microtubules contract & pull chromarids to opposite poles of the centromere
-chromatids are now daughter chromosomes

Question 7

Telophase

Answer 7

-Daughter chromosomes reach poles & uncoil & lengthen
-Nuclear envelope & nucleolus re-form
-2 nuclei are formed
-spindle fibres disintegrate

Question 8

Cytokinesis (animal cells)

Answer 8

-division of the rest of the cell (cytoplasm & organelles) after nucleus divides
-in animal cells cytoplasm pinches in
-in the plant cell the cell plate re-forms

Question 9

What must be done to enable chromosomes to be seen more clearly

Answer 9

Tissue must be stained

Question 10

Explain why the student is supposed to squash down with strong vertical pressure

Answer 10

-single layer of cells
-prevent tissues moving over each Föhr
-phases easily visible
-prevent dance of distribution of cells
-allow light to pass through

Question 11

Homologous Chromosomes

Answer 11

Have the same gene in the same locus

Question 12

Prophase 1

Answer 12

-chromatin condenses & becomes visible
-chromosomes visible as 2 chromatids
-centrioles move to opposite poles of the cell
-synapsis homologous pair of chromosomes come together to form a bivalent
-crossing over takes place between non-sister chromatids in the bivalent
-crossing over takes place between non-sister chromatids in the bivalent
-parts of each chromatid may break & reconnect to another chromatid
-chiasma (point of crossing over) pl chiasmata
-process results in recombination of maternal & paternal genetic information

Question 13

Metaphase 1

Answer 13

-spindle fibres attach to centromere & move chromosome to equator of the cell
-bivalents arrange themselves at the equator of the spindle
-homologous chromosomes arrange themselves randomly at the equator of the cell (random assortment) of homologous chromosomes leading to genetic variation