The causes of genetic mutatoins

Question 1

what is a mutation

Answer 1

this is a sudden change in genetic trait - it changes the DNA code

Question 2

the change is….

Answer 2

then heritable – somatic mutation is passed on to daughter cells and if its in a germ mutation is passed onto the next generation

Question 3

can mutations be good or bad

Answer 3

Both

• positive is that they drive evolutionary change
• the negative is that they cause many diseases

Question 4

what are the types of mutations that you need to know about

Answer 4

• point mutations
• frameshift mutations
• chromosomal mutations

Question 5

mRNA codon that you need to know about

Answer 5

• AUG = this is methionine and is a start codon

Question 6

describe point mutations

Answer 6

• Changes in a single base pair in DNA – these do not interfer much with protein function but can be bad

Question 7

what are the three types of point mutations

Answer 7

• Silent
• Missense
• Nonsense

Question 8

describe silent

Answer 8

• Three base codon changes but the same amino acid is coded

Question 9

describe missense

Answer 9

• Conserved – changes the amino acid coded but one that has similar properties
• Non-conservative – changes amino acid coded to one that has different properties

Question 10

describe non sense

Answer 10

• Leads to premature stopping of the amino acid sequence

Question 11

what are the two types of missense mutations

Answer 11

conserved and non conservative

Question 12

describe examples of point mutations

Answer 12

sickle cell anaemia

Question 13

describe sickle cell anaemia

Answer 13

• Mutation in a single nucleotide
• Causes change in amino acid from glutamic acid to valine – non conservative missense
• Glutamic acid is a charged amino acid whereas valine is hydrophobic
• Changes in the properties of haemoglobin molecules that carries oxygen to the cells

Question 14

what are the frameshift mutations

Answer 14

• Where a single base is added or deleted from the DNA
• Adding or deleting 1 base changes every amino acid in the protein after this point
• Proteins don’t function properly

Question 15

what is an example of frameshift

Answer 15

• tay-sacks disease

Question 16

describe tay-sachs disease

Answer 16

• Mutations in beta-hexosaminidase A (Hex-A)
• Most are point mutations (65/78)
• 8 frameshift mutations – 6 deletions and 2 insertions,

Question 17

what are deletions

Answer 17

part of chromosome is left out

Question 18

what are duplications

Answer 18

part of a chromosome breaks off and attaches to the sister chromatid

Question 19

what are inversions

Answer 19

part of a chromosome breaks off and reinserts backwards these don’t usually cause any problems as long as its balanced

Question 20

what are translocations

Answer 20

– part of a chromosome breaks off and attaches to a different chromosome
- changes gene location on chromosome and can change a number of copies of a gene

Question 21

what are examples of deletions

Answer 21

cri du chat

di George syndrome

Question 22

what are examples of duplications

Answer 22

Charcot marie tooth disease

Question 23

what are examples of translocation

Answer 23

XX* male syndrome

Question 24

describe cri du chat

Answer 24

• Partial deletion of the short arm of chromosome 5

- 90% are sporadic and de novo deletions

Question 25

describe di George syndrome

Answer 25

- Deletion of a region of a long arm chromosome 22 - Microdeletion - Majority of cases are de novo

Question 26

describe Charcot marie tooth disease

Answer 26

- Most common heritable peripheral neuropathy - 70-80% of cases duplication of large region of short arm of chromosome 17 - Includes gene peripheral myelin protein 22

Question 27

describe XX* male syndrome

Answer 27

- Translocation of SRY gene from Y chromosome to X chromosome

Question 28

describe nondisjunction

Answer 28

- Chromosomes fail to separate properly - Leads to trisomy – extra chromosome – diseases such as down syndrome - Monosomy – lack of chromosome – usually not viable and frequent in misccariages - Triploidy – 3 sets of chromosomes – banana plants, sterile and need clonal propagation, in humans triploid babies will miscarry or die within 1st year of life

Question 29

what are spontaneous mutations

Answer 29

- Arise from errors in replication processes and base modifications - Eukaryotes = rate 10-4 – 10-6 per gene per generation - Natural error rate for DNA polymerase - Many are corrected by cellular repair systems so are repaired before they are transmitted - Base modifications – depurination, deamination, tautomeric shift - Base insertion and deletion

Question 30

what are the origins of spontaneous mutations

Answer 30

can arise by 3 types of chemical changes - deprivation - deamination - tautomeric shift

Question 31

describe depurination

Answer 31

loss of purine base A or G

Question 32

describe deamination

Answer 32

changes a normal base to atypical base for example C to U, this can be corrected or 5-methylcyotisine to hypoxantine which is irreparable

Question 33

describe tautomeric shift

Answer 33

repositioning of hydrogen atoms that lead to mismatching, guanine will pair with thymine rather than cytosine

Question 34

what is a mutagen

Answer 34

it is an agent which causes genetic mutation

Question 35

what do mutagens do

Answer 35

they increase the number of mistakes from 1000 to 100,000 per replicated gene

Question 36

what are the types of mutagens

Answer 36

- physical - chemical - biological

Question 37

name the physical mutagens

Answer 37

- UV rays - radiation - extreme heat

Question 38

name the chemical mutagens

Answer 38

- nicotine - pesticides - methane

Question 39

name the biological mutations

Answer 39

- bacteria | - viruses

Question 40

what types of radiation is there

Answer 40

- direct | - indirect

Question 41

describe direct radiation

Answer 41

- When alpha particles, beta particles or x rays create ions which physically break sugar phosphate backbone, connections between base pairs or chemically alter bases - Bases held together by hydrogen bonds when broken - If two pyrimidines of the same type (T or C) are next to each other they bind to each other distoriting DNA

Question 42

describe indirect radiation

Answer 42

- Creation of free radicals where the presence of unpaired electrons damages bases or breaks backbone

Question 43

what does smoking cause

Answer 43

- 1,000,000 deaths due to lung cancer - Double strand breaks - Base pair trans-versions

Question 44

name infectious agents

Answer 44

- Human papilloma virus – viral DNA is incorporated into host and can disable normal DNA damage repair processes - Helicobacter pylori – infection can cause stomach cancer and can induce reaction oxygen species

Question 45

what is a codon

Answer 45

three adjacent nucleotides that Code for an amino acid

Question 46

name chromosomal mutations

Answer 46

- non dissection - deletion - duplication - inversion - translocation