Lecture 10

Question 1

Describe the events of the cell cycle and analyse data from the cell cycle experiments

Answer 1

In a dividing cell, the mitotic phase alternates with interphase (growing period).
G1 (first part of interphase) followed by S phase, when the chromosomes duplicate; G2 is the last part of the interphase.
In M phase, mitosis distributes the daughter chromosomes to daughter nuclei and cytokinesis divides the cytoplasm, producing two daughter cells

Question 2

What happens in G2 of interphase

Answer 2

G2 of interphase -
a nuclear envelope encloses the nucleus
Centrosomes have formed by duplication of single centrosomes.
Each centrosome contains two centrioles

Question 3

What happens in prophase

Answer 3

Nucleoli disappears
Chromatin fibres become more tightly coiled condensing into discrete chromosomes
Two identical sisters join at their centromere
Mitotic spindle begins to form (composed of centrosomes and microtubules)

Question 4

What happens in pro-metaphase

Answer 4

Nuclear envelope fragments
Chromosomes have become even more condensed
Two of the chromatids of each chromosome now has a kinetochore

Question 5

What happens in metaphase

Answer 5

Centrosomes are now at opposite poles of the cell

Chromosomes have arrived metaphase plate

Question 6

What happens in anaphase

Answer 6

Shortest stage
Begins when proteins are cleaved
Two sister chromatids part suddenly
Cell elongates as microtubules lengthen

Question 7

What happens in telephase

Answer 7

Chromosomes less condensed
Nucleoli reappear
Nuclear envelope arise from fragments of parent cell
Two identical nuclei formed

Question 8

What happens in cytokensis

Answer 8

The formation of a cleavage furrow, this pinches the cell in two
the cell divides itself to place the separate sets of chromosome into two individual daughter cells

Question 9

Explain the roles of centrosomes, kinetochores and microtubules in cell division and distinguish between them

Answer 9

Centrosomes - The main purpose of a centrosome is to organize microtubules and provide structure for the cell, as well as work to pull chromatids apart during cell division
Kinetochores - is a protein structure that forms on a chromatid during cell division and allows it to attach to a spindle fibre on a chromosome.
Microtubules - the migration of chromosomes to opposite ends of a mitosing cell during the anaphase

Question 10

Compare and contrast cytokinesis in animal and plant cells

Answer 10

During that stage, animal cells form furrow or cleavage that gives way to formation of daughter cells.
The rigid cell wall, don’t allow plant cells to form furrows.