Mutations

Question 1

What is exogenous DNA damage?

Answer 1

radiation, free radicals (uncharged mol with unpaired valency electron), chemicals, anti-cancer –> defective DNA repair –> MUTATION

Question 2

What is endogenous DNA damage?

Answer 2

DNA replication defects, transposable elements –> defective DNA repair –> MUTATION

Question 3

What are the 3 types of mutation on a micro level?

Answer 3

Deletion –> shorten = frame shift -1, can affect stop codon being read.

Insertion –> lengthen = frame shift = +1, can affect stop codon being read.

Substitution (missense) (nonsense = changed bp = becomes stop codon) –> change one for another: transition or transversion

Question 4

Define transition vs transversion

Answer 4

Transition –> purine to purine (A-G), pyrimidine to pyrimidine (T-C).

Transversion –> purine to pyrimidine or vice versa (A/G – C/T)

Question 5

What are the 5 types of mutation on a macro level?

Answer 5

Deletion –> a section removed.
Duplication –> a section duplicated.
Inversion –> a section flipped.
Substitution –> one section taken from one chromosome and added to another.
Translocation –> 1 piece on each chromosome swapped

Question 6

What is a synonymous mutation?

Answer 6

CHANGES MAY NOT ALWAYS HAVE AN EFFECT –> codes for same AA = neutral/silent, synonymous

Question 7

Describe what a frameshift mutation is

Answer 7

Deletion –> shorten = frame shift -1, can affect stop codon being read. Insertion –> lengthen = frame shift = +1, can affect stop codon being read,

Question 8

What is the difference between a missense mutation and a nonsense mutation?

Answer 8

Missense: substitute nt = becomes another AA, nonsense: substitute nt = become stop codon

Question 9

Outline the sickle cell mutation

Answer 9

Mutation in codon 7, 6th AA. Glu –> Val. Base substitution mutation

Question 10

What do mutations result from?

Answer 10

Errors in cell division, Ionising radiation, Chemicals, Viruses

Question 11

What is a spontaneous mutation?

Answer 11

germ line (first affected person)/somatic, if autosomal dominant and parent not affected = must be spontaneous, autosomal recessive mutation of same gene both chromosome = highly unlikely. Spontaneous mutation = heterozygote

Question 12

What is a germ line mutation?

Answer 12

eggs/sperm, affect all cells in body, passed on

Question 13

What is a somatic mutation?

Answer 13

body cell, not passed on, error in mitosis, can be genetic (DNA replication error) or chromosomal

Question 14

Describe mitochondrial mutations

Answer 14

often involve multiple organ systems, prominent in organs requiring a lot of energy (heart, brain, muscles), maternal inheritance

Somatic: limited ability to repair, mutations build up over time, may play a role in normal ageing, cancer.

Germ line: associated with defects in oxidative energy metabolism

Question 15

What happens in a cell with 2 copies of the same chromosome?

Answer 15

increase in expression of gene, if genes slow growth = fatal, if genes promote growth = grow uncontrollably = cancer

Question 16

Outline PGCs (Primordial Germ Cells) in female devel

Answer 16

PGCs arrive at ovary, diff into oogonia, undergo further mitosis, some enter prophase meiosis 1, arrest cell cycle = primary oocyte (surrounded by flattened epithelial = primordial follicle)

Question 17

Describe PGCs (Primordial Germ Cells) in male devel

Answer 17

PGCs arrive in testis, stay there until puberty. Puberty = spermatogonia diff to spermatozoa

Question 18

What are PGCs?

Answer 18

Primordial Germ Cells

Question 19

Why is the mutation rate higher in male gametes?

Answer 19

no. divisions higher then female gametes

Question 20

What is Aneuploidy?

Answer 20

presence of an abnormal number of chromosomes in a cell

Question 21

What happens to a foetus exposed to radiation?

Answer 21

death/aborted, teratogenesis (process by which congenital malformations are produced in an embryo or foetus) cancer when born

Question 22

What features would allow a germ cell mutation to be inheritable?

Answer 22

It would not be lethal to the gamete, It would not impair gamete function, It would not be lethal at fertilisation, It would allow the production of a viable adult with normal reproductive capacity

Question 23

What effect can mutations have on drug treatment?

Answer 23

mutation may lead to no effect of the drug, reduced effect, increased effect, side effects or an allergic reaction

Question 24

Describe loss of function vs gain of function in regard to mutations

Answer 24

In general recessive mutations cause loss of function and often affect biochemical pathways

In general dominant mutations cause increased function and often cause structural abnormalities

Question 25

what mutations could change the amount of gene product?

Answer 25

mutations affecting transcription/translation

alter promoter activity, prevent mRNA slicing, reduce mRNA stability