DNA Replication, Mitosis Amd Meiosis

Question 1

Describe the cell cycle

Answer 1

G1 = cell prepares for division ( cellular contents all replicated excluding chromosomes) has the cell arrest point (cell decides whether to continue or not)
S= DNA replication- each of the 46 chromosomes duplicated by the cell
G2= prepares for cell division by checking duplicated chromosomes for error and making any repairs
Mitosis
Cytokinesis

Question 2

When does DNA replication take place and what type of replication?

Answer 2

S phase

Semi conservative replication

Question 3

Describe what happens in initiation of DNA replication

Answer 3

Recognition of origin of replication
Helicase unravels DNA double helix
Requires specific proteins to interact with DNA and recruit DNA polymerase
DNA polymerase then acts in a 3’—>5’ direction (special enzyme needed to initiate each strand)

Question 4

Describe what happens in elongation

Answer 4

Polymerisation of incoming nucleotides
Leading strand 3’–>5’ Produced normally
Lagging strand produced 5’–>3’ produces Okazaki fragments. These then require DNA ligase to link up all the fragments forming the sugar phosphate backbone.

Question 5

Describe what happens in termination

Answer 5

As replication continues replication forks enlarge and eventually merge
2identical DNA molecules produced
DNA then wraps around his tones —->nucleosomes

Question 6

Describe interphase in mitosis

Answer 6

Before a cell can divide all genetic info is duplicated during the s phase of the cycle. Each chromosome now consists of 2 identical chromatids touching in structure called a centromere

Question 7

Describe the other phases

Answer 7

PROPHASE - chromatids replicate to sister chromatids and condense (chromosomes)
METAPHASE - chromosomes line up at metaphase plate
ANAPHASE - spindle fibres pull chromosomes apart
TELOPHASE - cytokinesis and nuclear envelope forms

Question 8

What does mitosis produce?

Answer 8

2 daughter cells with same chromosomal content as the parental cell (diploid)

Question 9

Meiosis is IPMST except ……

Answer 9

Metaphase - sister chromatids line up adjacent (allow for recombination)
Therefore anaphase pull adjacent chromosomes away from each other
Has a 2nd round (PMAT 2)
End up with 4 haploid cells, each having half the info of the parent and all non identical

Question 10

Consequences of mistakes in meiosis

Answer 10

1/3 of all identified miscarriages
Infertility
Leading cause of mental retardation