cell division and dna replication

Question 1

DNA replication

Answer 1

happens prior to cell division
- 2 identical DNA molecules are produced, they are semi-conservative as they contain one original strand and a new strand.
- 1) DNA double helix unwinds with the aid of helicase
-2) h bonds between n base pairs break (unwind)
-3) NUcleotides from within the nucleus ( Okazaki fragments) assemble opp each strand, using ATP to join them together.

Question 2

Mitosis

Answer 2

• cell division producing cells needed for growth and repair.
• produces 2 genetically identical daughter cells to their parents’ cells.
• mitosis occurs rapidly during early stages of growth, e.g seedlings, infants, root tips, embryos, zygotes and etc.
• Interphase, PMAT

Question 3

Cell Cycle

Answer 3

Interphase = G1+S+G2
M=Mitosis
G1= Growth (most growth - high rate of metabolic processes)
S= Synthesis of DNA
G2= Growth

Question 4

Mutations

Answer 4

Spontaneous and random, they result from chance.
- however, the rate of mutations could be determined by environmental factors and exposure to mutagens.

Question 5

Block mutations or chromosomal mutations

Answer 5

removal of entire genes or chromosomes

Question 6

Meiosis

Answer 6

Cell division that occurs in sex organs and produces Sex cells (Gametes).
- gametes produced are haploid. 23
- when they fuse in fertilisations, homologous chromosomes formed, therefore they become diploid 2n. 46
- occurs twice.

Question 7

Independent assortment

Answer 7

homologus pairs of chromosomes line up random order during metaphase 1 of meiosis.

Question 8

Segregation

Answer 8

the independent separation of alleles on different chromosomes.

Question 9

order of variation

Answer 9

Crossing over, INdependent Assortment, Segregation

Question 10

Crossing over linked genes

Answer 10

parts of non-sister chromatids can cross over at the chiasma. Exchanging segments of DNA, which result in different combinations of alleles. Resultant gametes = recombinants.