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Microbiology > Mutations > Flashcards

Mutations Flashcards

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Biology 101 flashcards
1
Q

What is a mutation?

A

Changes in the sequence of nucleotide of DNA
Inheritable
Harmful, lethal, helpful or silent

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2
Q

What is a point mutation?

A

Change in a single base
Most common
Silent missense and nonsense

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3
Q

What are spontaneous mutations?

A

Errors in normal processes

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4
Q

What are base analogs

A

Mismatch during replication e.g 5BrDU

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5
Q

What are intercalating agents

A

Insert extra bases eg ethidium bromide

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6
Q

What do agents that modify nucleotide bases do

A

Alter H bonding

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7
Q

What are UV mutagenesis

A

Faulty repair of thymine dimers

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8
Q

What are alkylating agents

A

Mutagens likely to introduce small changes and major changes

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9
Q

what is an example of base modicfictaion

A

nitrous acid as it converts adenine so it no longer pairs with thymine and modified adenine pairs with cytosine

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10
Q

what are nucleoside analogs

A

compounds that resemble bases closely- eg adenine and thymiine nucleoside

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11
Q

what is adenine nucleoside

A

2-aminopurine is incorportaed into DNA in place of adenine but can pair with cytosine so an AT pair becomes a CG pair

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12
Q

what is thymine nuceloside

A

5-bromouracil is an anticancer drug as it is mistaken for thymine by cellular enzymes but pairs with cytosine so AT pair becomes a CG pair

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13
Q

what happens when UV light passes through DNA

A

it becomes abnormal and results in a thymine dimer - the adjacent thymines become crosslinked, forming a thymine dimer and disrupts normal base pairing

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14
Q

what is the difference between endo and exonuclease

A

endo= cuts DNA
exo= Removes damaged DNA

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15
Q

What is a part of DNA replication

A

proofreading

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16
Q

what is the error rate for DNA polymerase without proof reading

A

1 - 1,000,000 nucleotides

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17
Q

what is the error rate for DNA repliaction

A

DNA polymerase error rate 1 in 10-9 nucleotides

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18
Q

what is the error rate for transcription

A

RNA polymerase error rate 1 in 10-5 nucleotides

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19
Q

what is the error rate for translation

A

Translation error rate 1 in 10-4 per codon

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20
Q

what does DNA ligase do

A

seals the remaining gap by joining old and new DNA (ineffcient repair leads to mutation)

21
Q

what are the types of mutation

A

Point= silent , nonsense and missense
Frameshift= insertion or deletion mutation
Chromosomal= duplication deletion and translocation
Repeat expansion= causes Huntington’s and fragile X syndrome

22
Q

what is a missense mutattion

A

a DNA chnage that reuslts in different amino acids being encoded at a particular position in the resulting protein. e.g sickle cell anemia
C-G becomes A-T and causes a change in the amino acid sequence and a new protein is released

23
Q

Explain Missense mutation and antibiotic resistance

A

Mycobacterium tuberculosis
Chronic lung infection
High fatality rate without treatment

Antibiotic rifampicin very effective
Binds to RNA polymerase
Inhibits transcription

Problem: high rate of point mutation in rpoB
Single base change
Single amino acid change
Reduced drug binding
RESISTANCE

24
Q

what is a nonsense mutation

A

stop mutation is a change in DNA that causes a protein to terminate or end its translation earlier than expected e.g protein CFTR leads to CF

25
Q

What is a silent mutation

A

no change in the polypeptide - change in the DNA sequence has no effect on the amino acid sequence E.g AAA codes for amino acid lysine and when mutated AAG can code for lys

26
Q

what is a frameshift mutation

A

in a gene refers to the insertion r deletion of a nucelotide bases in numbersthat are not multiple of three e.g crohns, CF and types of cancer
Shift in the reading frame and change in protein

27
Q

What are the codes for GLY

A

GGU, GGC, GGA and GGG

28
Q

What is vertical gene transfer

A

when genes are passed from organism to its offspring. Parent to daughter/offspring and is a part of reproduction

29
Q

what is horizontal gene transfer

A

occurs between mature cells and is not a part of reproduction and transfers from donor to recipient. It contributes to genetic diversity- brings organism new functions

30
Q

what are the 3 major mechanisms of horizontal gene transfer

A

transformation, conjugation and transduction

31
Q

what is transformation

A

genes transferred from one bacterium to another as “naked” DNA

32
Q

what is conjugation

A

plasmids transferred 1 bacteria to another via direct contact

33
Q

what is transduction

A

DNA transferred from 1 bacteria to another by a virus that infect bacteria (bacteriophage)

34
Q

what experiement looked into transformation

A

griffith experiment in 1928

35
Q

what does Natural transformation require

A

competence- Some bacteria are naturally competent.
Have DNA uptake proteins in cell membranes
Some competent all the time
Some competent only at specific stages in the growth phase.
Streptococcus pneumoniae, Bacillus subtilis, Haemophilus influenza, Neisseria gonorrhoeae.
Many other bacteria have been shown to contain the genes for natural competence but have never been observed to do so.

36
Q

what is the lytic phage cycle T4

A

where phages infect and repidly kill their infected host thereby shaping bacterial population dynamics and assissting in their long term evolution via generlised transduction

37
Q

what are the phases of T4

A

Adsorption, penetration, replication, maturation, release and reinfection
0 min= DNA injected
2 min= host DNA degraded
3 min= Phage DNA made
5 min= late RNA made
12 min= heads and tails made
13 min= heads filled
15 min= virions formed
22 min= host cell lysis

38
Q

What is the lysogenic phage life cycle

A

DNA is incorporated into the host genome, where it is passed onto subsequent generations. Environmental stressors such as starvation or exposure to toxic chemicals may cause the prophage to excise and enter the lytic cycle

39
Q

what can phage carry

A

more than the minimum requirement to replicate themselves.

40
Q

what is Diphtheria: Corynebacterium diphteriae

A

Respiratory infection
5-10% fatality rate
Bacterial toxin major virulence factor
Lysogenic Β-phage integrates into the bacterial DNA
Β-phage encodes the characteristic diphtheria toxin

41
Q

what is Conjugation in Bacteria

A

Transfer of DNA by contact of two bacterial cells Can transfer plasmid or chromosome

42
Q

what are plasmids

A

DNA elements capable of autonomous replication
Generally encode non-essential genes
Useful metabolic activities
Antibiotic resistance

size: 1 – 1000 kb
double stranded DNA
1 to >100 copies / cell

Some are transmissible to other strains
very abundant in nature
300 different plasmids identified in E. coli isolates

43
Q

what occurs in bacterial conjugation

A

Large amounts of DNA transferred
up to 200 kb
Some plasmids encode antibiotic resistances
R plasmids
Interspecies transfer possible
Plasmids “evolve” at a very rapid rate!

44
Q

what are the maintenance genes

A

ori, rep and inc

45
Q

what are the transfer genes

A

tra

46
Q

what are the Antibiotic Resistance genes

A

Tet
Sul
Str
Mer
Cat

47
Q

what happens in R Plasmid Evolution

A

Plasmids carrying multiple antibiotic resistances identified:mup to 18 different genes on one plasmid and use of one antibiotic selects for 17 other resistances!
Methods of picking up antibiotic resistance:
transposons
site specific recombination (integrons)
homologous recombination

48
Q

What is insertion

A

Addition of one or more nucleotides and causes a shift in the reading frame and leads to the synthesis of a different protein or a premature stop codon causeing a loss of function

49
Q

What is deletion

A

Removal of one or more nucleotides causing abframshift Protein can be truncated it functional and leads to disorders

Microbiology (29 decks)

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