Lecture 8 - How Are Genetic Changes Generated and Inherited?

Question 1

How are genetic changes generated?

Answer 1

• errors in replication - causing mutations
• DNA repair processes aren’t always effective
• external impacts + stress - causing mutations
• induced mutations in the lab

Question 2

why are mutations important in biology?

Answer 2

• viability - most neural/deleterious
  
  • diploid - less likely to have an effect
  • haploid - more likely to have an effect and be deleterious
• genetic diversity - variation
• germ line mutations - passed to offspring
• somatic mutations - can cause disease - cancer
• diversity in microbes - cause AMR
• genetic mapping
• genetic screens

Question 3

What types of mutation will be recessive or dominant?

Answer 3

• loss of function - recessive
• gain of function - dominant

Question 4

What are 4 examples of mutations?

Answer 4

• single base changes
• deletions / insertions
• DNA replication slippage
• bigger issues (chromosome)

Question 5

What is the effect of UV radiation on the DNA sequence?

Answer 5

• can cause adjacent thymine bases to become covalently linked as thymine dimers
• nucleotide excision repair pathways recognises and removes these
• nuclease cuts before and after thymine dimer to remove it
• polymerase replaces complementary nucleotides

Question 6

Explain the Ames test for mutagenicity

Answer 6

• potential mutagen
• histadine-dependent salmonella
• homogenised liver extract
  mixed and plated on agar medium lacing histidine
• incubated
• plates which have lots of mutagen grown are carcinogenic

Question 7

What is the Ames test?

Answer 7

A test to determine a carcinogen by measuring the ability of the chemical to reverse the histamine-dependant mutation in the strain of salmonella used

Question 8

What is an oncogene?

Answer 8

• a gene that the protein causes cancer
• because of mutations in a regular gene has resulted in It being overactive
• dominant

Question 9

What is a tumour suppressor?

Answer 9

• a gene that encodes a protein that restrains cell proliferation
• loss of this gene increases likelihood of cancer
• recessive - needs to loose in both copies

Question 10

What is S phase?

Answer 10

DNA replicates

Question 11

What is M phase?

Answer 11

mitosis
cytokinesis

Question 12

What are G1 and G2?

Answer 12

growth phases

Question 13

What 3 things are important about cell cycle?

Answer 13

1) order of events
2) once per cell
3) fidelity of events - correctly copied

Question 14

what do cyclin dependent kinases (CDKs) need to be fully active and what do they form?

Answer 14

• cyclin
• cyclin - CDK complexes

Question 15

What is the role of cyclin-CDK complexes?

Answer 15

regulate cell cycle

Question 16

Explain cyclin concentration throughout the cell cycle and what this means for cyclin dependent kinases

Answer 16

• cyclin accumulates going into mitosis
• then degrades
• activity of cyclin-CDK complexes increases asa the concentration of cyclin decreases

Question 17

What holds sister chromatids together and when does this happen?

Answer 17

• cohesin rings - causing cohesion
• during S phase

Question 18

What is the role of the kinetochore?

Answer 18

bind the spindle microtubules

Question 19

Why is it so important that sister chromatids are held together?

Answer 19

• bi orientation - so that they are attaching to opposite poles
• has to happen before anaphase

Question 20

What is aneuploidy?

Answer 20

incorrect number of chromosomes

Question 21

What happens at the M checkpoint?

Answer 21

cell will wait here of there is:
- spindle damage
- connection issues
as there will not be biorientation

Question 22

What is the S + G2 checkpoint called?

Answer 22

cell will wait if there is DNA damage