Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

LF104: Molecules, Cells And Organisms > Lecture 38. Mutagenesis and Mutations > Flashcards

Lecture 38. Mutagenesis and Mutations Flashcards

1
Q

How can mutants be created?

A

Mutants can be spontaneous or a result of being exposed to mutagens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What can bacteria produce to protect from radiation damage?

A

Melanin and other molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How often does E coli DNA make a substitution?

A

~1 in every 10⁷ bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How long is the E. coli genome?

A

5.4 x10⁶ base pairs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Spontaneous mutation examples

A

Replication errors - Wrong base inserted by DNA polymerase
Wrong base inserted by DNA polymerase - Tautomers forms have different H-bonding pattern
Base pair slipping - Repeat nucleotides can lead to frameshift mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are mutagens?

A

Chemical or physical agents causing damage to DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Examples of mutagens

A

Nitrous acid, Reactive oxygen species, Alkylating agents, Intercalating agents and UV light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Intercalating agents

A

Usually have flat multiple ring structures
Binds between base pairs
Distorts the helix
Can also lead to frameshift mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Intercalating agent example

A

Ethidium bromide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a point mutation?

A

A change to one base pair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a transition substitution?

A

A change from purine to purine or pyrimidine to pyrimidine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a transversion substitution?

A

A change from a purine to a pyrimidine and vice versa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What could result in segregation of mismatched base pairs?

A

Error in replication, tautamerisation or damage such as deamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Consequences of point mutations in non-coding DNA

A

May have no consequence at all, but non-coding DNA can have other functions e.g. promoters and other regulatory sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Consequences of point mutations in promoters

A

Can affect transcription (up or down) but may have no consequence at all

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Consequences of point mutations in genes under control of promoter

A

Protein coding part: Depends
Can affect sequence or regulation of translation

17
Q

What are the three kinds of mutations caused by substitutions?

A

Silent, Missense and Nonsense

18
Q

Silent mutation

A

Nothing happens. Genotype changed but no change in phenotype

19
Q

Missense mutation

A

Often nothing happens but can be detrimental. Genotype changed and phenotype may be changed

20
Q

What mutations occur due to insertions and deletions?

A

Frameshift mutations

21
Q

Nonsense and frameshift mutations

A

Usually detrimental but can be tolerated close to C-terminus. Genotype and phenotype changed

22
Q

Deletions

A

Can remove kilobases and lose several genes or be just a single base pair
Can result in frameshift mutations one or a few bases are lost within a gene affecting coding or regulation

23
Q

Inversions

A

Can flip kilobases and several genes or be much shorter
Can disrupt genes or just invert them

24
Q

Tandem repeats

A

Part of genome is duplicated
Can lead to overproduction of proteins encoded in the duplicated region
Also leads to evolution of proteins

25
Q

Transposons

A

Transposons are nucleotide sequences that are able to move themselves around
Can disrupt genes

26
Q

Reversions of mutations

A

Reversion is a point mutation resulting in restoration of the original sequence

27
Q

Supressor mutations

A

A second mutation happens that results in the original phenotype being restored

28
Q

Intragenic suppression

A

A second mutation occurs in a different gene to the one in which the first mutation occurs.
The effect is to suppress the phenotype of the first mutation

29
Q

Nonsense suppression

A

Strains with nonsense suppressors are normally sick because cell tends to translate past normal stop codons and produce longer proteins than normal.
These may not function correctly because they may fold incorrectly.

30
Q

Making histadine auxotroph

A
  1. Expose to mutagen
  2. Grow in complex medium to allow expression of phenotype
  3. Penicillin enrichment: Change medium to minimal medium, add penicillin, penicillin will kill any growing bacteria, auxotrophs will not grow
  4. Plate on minimal medium + histidine and grow
31
Q

What is phenotype lag?

A

Phenotype is not seen for several generations

32
Q

What is cross feeding?

A

Metabolites immediately before block will accumulate If metabolite can diffuse from cell another bacteria can take it up. Both mutants can now grow but dependent on each other

33
Q

What is the Ames test used for?

A

Used to identify chemicals that are mutagenic and therefore carcinogenic. Assumes that if chemical is mutagenic to bacteria it is also mutagenic to humans

34
Q

What bacteria does the Ames test use?

A

A His auxotroph of Salmonella typhimurium

35
Q

What do the results of an Ames test show?

A

If chemical is mutagenic then lots of reversions
If not mutagenic only a few reversions

LF104: Molecules, Cells And Organisms (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions