25 - Cell Division And The Cell Cycle

Question 1

What are HeLa cells

Answer 1

Human cervical cancer cells
- name from Henrietta Lacks, died aged 31 from aggressive cervical cancer

Question 2

Phases of mitosis and cytokinesis in mammalian cells

Answer 2

• interphase (G2)
• prophase
• metaphase
• anaphase
• telophase
• interphase (G1)

Question 3

Method for viewing nuclear material

Answer 3

FISH - fluorescent in situ hybridisation
- cells grown on glass slides
- cells fixed and permeabilised with detergent
- cells incubated with fluorescent oligonucleotide probes specific for individual chromosomes

Question 4

Interphase G2 process

Answer 4

• Primers hybridise with their targets
• chromosomes become ‘painted’
• interphase chromosomes occupy their own distinct territories
• dispersed structure allows access of transcription factors to DNA
• cells actively making RNA and proteins
• meaning interphase cells are not resting

Question 5

Why are cells not resting in interphase

Answer 5

Actively making RNA and proteins, preparing for mitosis

Question 6

Prophase mechanism

Answer 6

Early prophase:
- centrosomes, each with a centriole, moves to opposite poles of animal cell
- chromosomes condense and become visible as long threads
- nuclear membrane begins to disaggregate into small vesicles
- nucleus is surrounded by interphase microtubules

Late prophase:
- chromosome condensation complete
- each chromosome now consists of two sister chromatids held together at centromeres
- microtubular spindle fibres grow from region adjacent to centromeres
- some fibres extend pole to pole, others attach to chromatids at kinetochores

Question 7

Metaphase process

Answer 7

• Chromosomes align midway between the poles to form metaphase plate
• ## sister chromatids remain attached

Question 8

Multiple myeloma condition info and cause

Question 9

Anaphase process

Question 10

Telophase process

Question 11

Interphase G1 process

Question 12

Three divisions in interphase

Answer 12

G1
S
G2
- then mitosis occurs

Question 13

Cyclic expression and use in cell division

Answer 13

Cyclic is made continuously in dividing cells
- cyclin accumulates and peaks just before cell division, and is destroyed as cell division occurs
- so cyclin is a concentration dependent controller of cell division

Question 14

Cyclin function in cell division

Answer 14

Acts as a concentration dependent controller of cell division, in partner with a CDK - a cyclin dependent kinase

Question 15

Who discovered role of cyclin

Answer 15

Sir Tim Hunt, 1983

Question 16

Cyclin - level of complexity and function as controller of cell division

Answer 16

• Cyclin require a partner (a CDK - cyclin-dependent kinase) before they can operate
• in all known surviving, naturally occurring eukaryotic organisms, there are multiple CDK heterodimers/controlling cyclins
• additional layers of cyclin function - multiple CDK inhibitors and activators, and their regulation in turn
• cyclin/CDK complexes are also controlled by destructive phases that reduce their concentration after they have performed their functions