Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Recombinant DNA Technology > L2 Prokaryotic Genomes > Flashcards

L2 Prokaryotic Genomes Flashcards

(75 cards)

Start Studying
1
Q

What is the typical shape of bacterial chromosomes?

A

circular

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

what type of molecule makes up bacterial chromosomes?

A

double-stranded DNA

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

Why are circular chromosomes considered more stable than linear ones?

A

Because they have no ends that can degrade

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

What challenge does circular DNA face within bacterial cells?

A

it takes up a lot of space and requires packaging due to DNA’s negative charge repulsion.

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

What helps package bacterial DNA tightly in the cell?

A

supercoiling and DNA-binding proteins

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

Where is the bacterial genome located?

A

In the cell cytoplasm

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

What is DNA supercoiling?

A

Twisting and coiling of DNA to compact it

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

What does supercoiling require to occur?

A

Energy input to overcome repulsion from negative charges

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

What is a downside of DNA supercoiling?

A

It makes accessing genes more difficult

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

Where does bacterial chromosome replication typically start?

A

A single origin called oriC

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

In which direction does bacterial chromosome replication occur?

A

Bi-directionally

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

How does bacterial chromosome replication relate to cell division?

A

It is timed to coincide with cell division

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

What happens to the chromosome during bacterial cell division?

A

One complete copy goes to each daughter cell

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

Why must bacterial replication be both fast and accurately timed?

A

So genome copies are at opposite ends of the cell before division.

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

What is notable about bacterial chromosomes at the time of cell division?

A

They may have already begun replicating again

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

what do most genes (open reading frames) in bacterial genomes encode?

A

mRNAs, which in turn encode proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are operons?

A

Clusters of ORFs that are transcribed together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Give an example of a gene that encodes structural RNA rather than mRNA

A

16S rRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How are transcription and translation related in bacteria?

A

They are physically coupled and occur simultaneously

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

At what level is bacterial gene expression primarily controlled?

A

At the level of transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What roles do non-coding DNA play in bacterial genomes?

A

It is often involved in gene expression; there is very little ‘junk’ DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is genome “decay”?

A

The process by which unnecessary genes are lost over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How much can bacterial chromosomes vary in size?

A

from less than 1Mb to over 10 Mb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does bacterial genome size variation compare to that of eukaryotes?

A

It is much less - eukaryotic genome size varies by up to five orders of magnitude

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Why do environmental bacteria tend to have large genomes?
Because they need to adapt to changing environments
26
How is gene expression managed in bacteria with large genomes?
it is tightly regulated
27
Why do bacteria in narrow niches (e.g. intracellular pathogens) have smaller genomes?
They live in stable environments and so only need core, "housekeeping" genes
28
What are "housekeeping" genes?
Genes that encode essential, core functions.
29
Is gene essentiality a fixed property?
No, it can change depending on the environment
30
What causes mutations during DNA replication in bacteria?
errors made by DNA polymerase
31
What types of point mutations can occur?
Transitions (same type of base) and transversions (different type of base)
32
What are other small-scale mutations caused by replication errors?
Insertions or deletions of 1-2 bases
33
Why is the inherent mutation rate low during replication?
because of DNA polymerase proofreading
34
What factors can increase DNA polymerase error rates?
DNA damage, fast replication, and mutagens
35
What are examples of mutagens?
Base analogues and chemically damaged bases (e.g. from radiation or oxidative stress)
36
How is the mutation rate in a gene related to its importance?
Essential genes have lower observed mutation rated because mutations are often lethal
37
What is recombination in bacterial genomes?
The movement of DNA sequences within the genome, not mutation
38
What happens when recombination occurs between inverted sequences?
The DNA between the inverted repeats is inverted
39
What happens when recombination occurs between direct repeats?
One copy of the repeated sequence and everything between them can be deleted
40
What is a slow way for bacteria to gain new phenotypes?
Gene duplication followed by divergent evolution
41
How can gene loss affect a bacterium's phenotype?
Loss of regulatory genes can significantly alter phenotype
42
What are plasmids?
circular double-stranded DNA molecules that can be part of the genome
43
How do plasmids spread genes between bacteria?
Horizontal gene transfer
44
What can transposable elements do in bacterial genomes?
Move chromosomal genes onto plasmids via transposition.
45
What is transposition?
The movement of DNA sequences (transposons) within or between DNA molecules
46
How do phages contribute to genetic variation in bacteria?
By inserting into chromosomal genes during infection (specialised transduction), sometimes carrying genes
47
what is a prophage?
A phage genome integrated into a bacterial chromosome
48
How can losing a gene result in a gain of function?
if a repressor or regulatory gene is lost, it may activate other functions
49
how do plasmids replicate?
Some replicate independently, others use host functions, starting from oriV
50
What determines whether a bacterium can carry multiple plasmids?
plasmid compatibility
51
How are plasmids typically acquired?
By conjugation, a chance event involving physical contact between bacteria
52
What happens during conjugation?
A plasmid is copied and transferred through a small channel from one bacterium to another.
53
What determines whether a newly acquired plasmid is maintained?
Natural selection
54
What are "selfish plasmids"?
plasmids that persist even if not beneficial, sometimes by forcing the host to retain them.
55
Why can plasmids be costly for bacteria to maintain?
because they can impose a fitness cost by using resources.
56
What is an insertion sequence (IS)?
a mobile DNA element that can disrupt genes or activate gene expression
57
What enzyme do insertion sequences encode?
Transposase
58
What sequences are required for insertion sequences to move?
Inverted repeat (IR) sequences
59
How can insertion sequences kill gene function?
By inserting into a gene and disrupting its proper reading
60
What role can insertion sequences play in recombination?
They can form sites that lead to deletion of chromosomal sections
61
How do insertion sequences help transfer genes to plasmids?
by acquiring genes and moving them onto plasmids.
62
What is a composite transposon?
A transposon made of two insertion sequences flanking one or more genes
63
How do composite transposons move genes?
via cut and paste transposition, often followed by mutation fixation
64
What ensures the whole composite transposon is moved?
the transposase recognises the flanking inverted repeats and moves the entire segment
65
What determines whether a transposed gene spreads in a population?
whether it provides an advantage under natural selection
66
Where are complex transposons typically found?
On plasmids, but they can move to chromosomes and back.
67
What additional genes do complex transposons carry beside transposase?
A resolvase gene
68
What does the resolvase gene enable?
Copy and paste movement of the transposon
69
What is SCCmec?
A complex transposon in Staphylococcus aureus that confers methicillin resistance (MRSA).
70
How does SSCmec move?
Using a combination of conjugation and transduction mechanisms
71
What is an integron?
A genetic element that captures gene cassettes using an integrase enzyme
72
What enzyme enables integrons to capture gene cassettes?
integrase
73
How are integrons mobilised?
As part of a composite transposon onto plasmids
74
What is the main function of integrons in bacteria?
To mix and match genes, often antibiotic resistance genes.
75
Why are integrons considered important in bacterial evolution?
Because they facilitate rapid acquisition of new traits like antibiotic resistance

Recombinant DNA Technology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions