Lecture 15

Question 1

The key roles of cell division

Answer 1

the ability of organisms to reproduce best distinguishes living things from non-living matter

the continuity of life is based on the reproduction of cells or cell division

Question 2

Why do cells divide?

Answer 2

to pass on genetically identical information to offspring

Question 3

The cell cycle

Answer 3

the life of a cell from the time it is formed form a parent cell until its own division into two cells

cell division is only a small part of the cell cycle

Question 4

Cell division importance in multicellular organisms

Answer 4

development from a fertilised cell
growth
repair

Question 5

cell division

Answer 5

most cell division results in daughter cells with identical genetic information

All the DNA in a cell constitutes the cells genome

a genome can consist of a single DNA molecule or a number of DNA molecules

DNA molecules in a cell are packaged into chromosomes

Question 6

Somatic cells

Answer 6

non-reproductive cells

two sets of chromosomes

Question 7

Gametes

Answer 7

reproductive cells

have half as many chromosomes as somatic cells

Question 8

Distribution of chromosomes during cell division

Answer 8

in preparation for cell division, DNA is replicated and the chromosomes condense

each duplicated chromosomes have two sister chromatids, which separate during cell division

the centromere is the narrowest waist of the duplicated chromosome, where the two chromatids are most closely attached

Question 9

Eukaryotic cell division consists of:

Answer 9

mitosis (division of nucleus)
cytokinesis (division of cytoplasm)

Question 10

Meiosis

Answer 10

yields non-identical daughter cells that have only one set of chromosomes, half as many as the parent cell

Question 11

Phases of the cell cycle

Answer 11

mitotic (M) phase (mitosis and cytokinesis)
interphase (cell growth and copying of chromosomes in preparation for cell division)

Question 12

Mitosis- 5 phases

Answer 12

prophase
prometaphase
metaphase
anaphase
telophase

Question 13

The mitotic spindle

Answer 13

is an apparatus of microtubules that controls chromosomes movement during mitosis

during prophase assembly of spindle microtubules begins int he centrosome, the microtubule organising centre

the centrosome replicated forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out of them

Question 14

An aster

Answer 14

a radial array of short microtubules

extends from each centrosome

Question 15

Spindle in pro metaphase

Answer 15

some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes

Question 16

The mitotic spindle at metaphase

Answer 16

• condensed chromatin
• mitotic spindle is made of tubule
• chromosomes bind to spindle via kinetochores
• the kinetochore is bound to centromeric DNA

Question 17

Mitotic spindle at anaphase

Answer 17

sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell

microtubules shorten by depolymerising at their kinetochore ends

Question 18

How do we know which end microtubule shorten

Answer 18

microtubules were labelled fluorescently

photobleaching was used to recolour a section of the microtubule

as the chromosomes moved towards the poles, the pole-side Mts stayed the same length but the kinetochore side Mts shortened

Question 19

Non-kinetochore microtubules

Answer 19

from opposite poles overlap and push against each other elongating the cell

Question 20

Cytokinesis

Answer 20

in animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow

in plant cells, a cell plate forms during cytokinesis