Mitotic cell cycle

Question 1

Chromosomes

Answer 1

Thread like structures containing DNA
The DNA is wrapped around histones (globular proteins)
Each chromosome is made up of two identical structures called chromatids
Each chromatid contains one DNA molecule
The chromatids are joined at the centromere
Telomeres are both ends of each chromatid

Question 2

Mitosis

Answer 2

Nuclear division that produces two genetically identical daughter nuclei

Question 3

Why are genetically identical daughter cells important

Answer 3

Growth, repair and asexual reproduction
Growth: Multicellular organisms grow from unicellular zygotes, each cell must have the same genes as in the zygote
Repair and replacement of tissues: Tissues and cells are constantly needing to be repairs or replaced so the new ones need to be genetically identical to perform proper function, they’ll also get rejected if they’re genetically different
Asexual reproduction: anew individuals from a single parent (plants)

Question 4

Cell cycle

Answer 4

Regular sequence of events that takes place between cell divisions

Question 5

Interphase

Answer 5

First phase of the cell cycle
Takes up most of the cycle
Has 3 sub phases (G1,S,G2)

Question 6

G1

Answer 6

First growth phase

RNA, enzyme and protein synthesis occurs

Question 7

S

Answer 7

Replication phase
DNA synthesis occurs
Relatively short

Question 8

G2

Answer 8

Second growth phase
Cell continues to grow
DNA is checked and errors repaired

Question 9

Mitosis is made up of 4 sub phases these are

Answer 9

Prophase
Metaphase
Anaphase
Telophase

Question 10

Prophase

Answer 10

The chromosomes condense and become visible as two chromatids
The centromeres have replicated and move apart
The spindle begins to form
The nuclear membrane breaks down
The nucleolus disappears

Question 11

Metaphase

Answer 11

The centromeres reach the poles

The chromosomes line up on the equator and there centromeres are attached to the spindle

Question 12

Anaphase

Answer 12

The spindle fibres shorten and pull the chromatids apart at the centromeres
They become chromosomes as soon as they’re separated

Question 13

Telophase

Answer 13

The chromosomes reach the poles
The spindle breaks down 
Chromatids uncoil to form chromatin
A new nuclear envelope forms 
The nucleolus reforms and the cytoplasm constricts

Question 14

Cytokinesis

Answer 14

The cytoplasm will divide by constructing inwards and pinching to separate into two cells

Question 15

Telomeres

Answer 15

Short regions of DNA at the ends of chromatids made of multiple repeat sequences
Main function is to ensure that when DNA is replicated the ends of the molecule are included in the replication and not left out
Without them the genes at the end would be lost and the chromosome would become shorted each time the cell divides
Prevent loss of genes during cell division

Question 16

Stem cell

Answer 16

Cell that can divide an unlimited amount of times
When it divide each new cell has the potential to remain as a stem cell or to develop into a specialised cell
Important for cell replacement and tissue repair as the more “committed” cells become to particular roles, the more they lose their ability to divide until in the adult most cells don’t divide

Question 17

Uncontrolled cell division can

Answer 17

Result in the formation of a tumour