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Mutations Flashcards

(49 cards)

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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

Study These Flashcards
A

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

21
Q

what are the types of mutation

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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

Study These Flashcards
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

Study These Flashcards
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

Study These Flashcards
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
What is a silent mutation
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
what is a frameshift mutation
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
What are the codes for GLY
GGU, GGC, GGA and GGG
28
What is vertical gene transfer
when genes are passed from organism to its offspring. Parent to daughter/offspring and is a part of reproduction
29
what is horizontal gene transfer
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
what are the 3 major mechanisms of horizontal gene transfer
transformation, conjugation and transduction
31
what is transformation
genes transferred from one bacterium to another as “naked” DNA
32
what is conjugation
plasmids transferred 1 bacteria to another via direct contact
33
what is transduction
DNA transferred from 1 bacteria to another by a virus that infect bacteria (bacteriophage)
34
what experiement looked into transformation
griffith experiment in 1928
35
what does Natural transformation require
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
what is the lytic phage cycle T4
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
what are the phases of T4
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
What is the lysogenic phage life cycle
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
what can phage carry
more than the minimum requirement to replicate themselves.
40
what is Diphtheria: Corynebacterium diphteriae
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
what is Conjugation in Bacteria
Transfer of DNA by contact of two bacterial cells Can transfer plasmid or chromosome
42
what are plasmids
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
what occurs in bacterial conjugation
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
what are the maintenance genes
ori, rep and inc
45
what are the transfer genes
tra
46
what are the Antibiotic Resistance genes
Tet Sul Str Mer Cat
47
what happens in R Plasmid Evolution
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
What is insertion
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
What is deletion
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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