Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Y2 Mol Bio > Genetics > Flashcards

Genetics Flashcards

(63 cards)

Start Studying
1
Q

Which phase can individual chromosomes be distinguished?

A

Metaphase

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

What is a karotype?

A

Organised representation of all the chromosomes in a eukaryotic cell at metaphase as they condense

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

Describe the different types of DNA coiling

A

(heterochromatin)- 30nm
(euchromatin)- 10nm

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

What histones are contained in a typical nucleosome?

A

2 H2A
2 H2B
2 H3
2 H4

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

What do the N-terminals of histone subunits do?

A

Interact with other proteins
Facilitate regulation and function of chromatin

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

What do linker histones (e.g H1) do?

A

Attach DNA onto histone octamers, limiting DNA movement
Stabilises formation of 30nm fibre which is transcriptionally silent
Rich in Lys and Arg, making it basic and can bind DNA
The chromatin scaffold can be remodelled to accommodate protein complexes for gene transcription and DNA replication

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

What does interphase chromatin contain which condense and decondense?

A

Set of fractal globules (globules within globules) which condense and decondese without knotting

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

What is contained in the nuclear periphery of interphase cells?

A

Transcriptionally inactive DNA
RNA transcripts are excluded

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

What do specialised DNA sequences ensure for complete interphase?

A

Facilitates complete DNA replication
Segregation of duplicated chromosomes in cell division

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

What does telomerase synthesise?

A

TTAGGG repeats on the 3’ overhang of chromosomes

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

How are centromeres defined?

A

171bp alpha satellite repeats that form condensed chromatin with histone octamers

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

What do kinetochore inner plate proteins bind to?

A

alpha satellite DNA

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

What do kinetochore outer plate proteins bind to?

A

protein components of the mitotic spindle

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

Describe a yeast centromere bound to a microtubule

A

Single nucleosome of centromeric chromatin is linked to a single microtubule with a basket structure

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

What increases with biological complexity?

A

Protein coding DNA
Non-protein coding DNA

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

What does non-protein coding DNA encode?

A

regulating transcription and organising access to protein-coding genes
Cis-regulatory information which determines when and where adjacent protein coding genes are transcribed

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

Describe transposons

A

Mobile genetic elements that jump around the genome
Can be non-replicative and replicative

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

Give three examples of transposons

A

P-element in flies, Activator/dissociator in maize where coloured kernals jump around the genome, Tn3/Tn10 in E.coli

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

Describe retroviral-like transposons

A

Replicate via RNA intermediates
Produce new DNA copies which integrate at new genomic locations
Self-encoded reverse transcriptase
Do not encode fully active infective viruses

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

Describe non-retroviral transposons

A

Abundant in vertebrate genomes
Replicates via an RNA intermediate with its own reverse transcriptase
Replicative

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

Give some examples of non-retroviral transposons

A

LINEs
SINEs
Human L1 elements
Human Alu elements
Mouse B1 elements

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

Describe an L1 insertion in humans

A
  1. L1 RNA synthase generates an ssRNA strand
  2. An endonuclease cleaves the first strand of target DNA
  3. DNA-primed reverse transcription takes place and a complimentary strand is synthesised
  4. The strand reintegrates with the inserted gene
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is an example of a disease caused by an L1 insertion?

A

Haemophilia

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

What initiates DNA synthesis at molecular level?

A

DNA helicase forming a replication fork

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What machinery is involved in DNA replication?
DNA helicase- spliting DNA strands DNA primase- synthesise short RNA primers Sliding clamp Clamp loader DNA polymerase- adds nucleotides
26
What does DNA polymerase require to add nucleotides?
A pre-existing primer chain Polymerase extends the RNA primer once it is in place
27
What removes the RNA primer from DNA?
Ribonuclease H
28
When the RNA pirmer is removed from DNA, what seals the nick?
DNA ligase
29
What can mutations in DNA helicase lead to?
Werner syndrome (premature aging) Autosomal recessive in RecQ helicase gene WRN
30
What can a loss of function mutation in RecQ-family DNA helicase lead to?
Bloom syndrome- extreme sensitivity to sun exposure Autosomal recessive
31
What increases the processivity of DNA polymerases?
Sliding clamp helps move DNA pol forward When DNA pol interacts with the primer, template junction is maintained and nucleotides are rapidly added
32
What keeps the sliding clamp close to the primer:template junction?
Clamp loader
33
How is ssDNA kept available as a template during semi-conservative replication?
ssDNA binding proteins (SSBs) which keep the replication fork open and allow DNA pol to function
34
Describe DNA topoisomerases
Prevent DNA becoming tangled during replication, increasing processivity of DNA pol This is because helicase unwinding parental DNA at the replication fork introduces tension in DNA Topoisomerases nick and reseal DNA
35
What is the difference between type I and type II DNA topoisomerases?
Type I- nick and reseal 1 DNA strand (no ATP) Type II- nick and reseal both DNA strands (requires ATP)
36
What is the difference between human and yeast origins of replication?
Yeast- autonomously replicating sequences (ARS) Human- sequences near LMNB2, MYC
37
Why is initiation of eukaryotic DNA replication biphasic?
Two stages: 1. Replicator selection in G1 phase where pre-replicative complex forms 2. Origin activation occurs at the start of S-phase where DNA unwinds and DNA polymerase is recruited
38
What does temporal selection when initiating DNA replication ensure?
Each origin is used and each chromosome replicates once per cell cycle
39
What does an origin recognition complex bind to?
Replicator sequence in the origin, e.g ARS in yeast
40
Outline formation of the pre-recognition complex in G1 phase?
1. The ORC binds to the replicator sequence 2. Cdc6 and Cdt1 bind to the ORC 3. Helicase Mem2-7 binds and the pre-recognition complex forms
41
What activates the pre-recognition complex?
Cyclin-dependent kinase (Cdk) in S-phase. This inhibits new pre-recognition complexes forming
42
What ensures chromosomes are replicated exactly once per cell cycle?
There is close relationship between pre-RC function, Cdk levels and cell cycle
43
How is DNA replication finished with the unsealed gap?
At chromosome ends, pol or ligase haven't sealed a gap. This is next to an RNA primer which is removed by ribonuclease H, shortening newly synthesised DNA strands at the 5' ends This can risk losing valuable coding information- premature aging and mutations
44
Outline how telomerase functions
1. Adds TTAGGG repeats on 3' end to compensate for loss of telomere sequences from RNA primer removal 2. DNA primase binds and initiates RNA primer synthesis 3. DNA polymerase extends this as an extra okazaki fragment
45
What is the telomerase shuffle?
Telomerase RNA component acts as a template where the telomere repeat sequences are synthesised in a step-wise process
46
When there are errors in DNA, what can happen to it?
DNA repair cell death Stay mutated and replicate
47
What are some endogenous causes of DNA damage?
Reactions with other molecules in the cell Hydrolysis Reactive oxygen species
48
What are some exogenous causes of DNA damage?
UV X-rays Carcinogens Chemotherapies
49
What are some consequences of endogenous DNA damage?
Depurination Deamination Methylation Replication errors
50
What are some consequences of exogenous DNA damage?
Pyrimidine dimers Double strand links Interstrand crosslinks
51
Are transversions or transition mutations more likely>
Transitions (pyrimadines to pyrimidine, vice versa)
52
Explain the outcome of a depurination of adenine
A purine is cleaved off by the N-glycosidic bond, causing a wobble base A frameshift can occur, generating missense proteins
53
What mutations can UV light cause?
Pyrimidine dimers due to DNA to distorting Interstrand DNA crosslinks- DNA cannot unwind for replication DNA-protein crosslinks
54
What can induce single strand breaks in DNA?
X-rays Ionising radiation Topoisomerase II inhibitors
55
What can induce double strand breaks in DNA?
ROS Hydroxyurea Camptocthecin
56
Outline base excision repair (BER)
1. DNA glycosylase removed damaged base 2. AP endonuclease and phosphodiesterase remove the sugar phosphate 3. Pol and ligase add a new nucleotide and seal the nick Repairs abasic sites and deamination
57
Outline nucleotide excision repair (NER)
Endonuclease cuts phosphate bonds DNA helicase removes short stretches of ssDNA. Pol and ligase seal the nick
58
Outline how translesion DNA polymerase replicates damaged DNA
1. When polymerase encounters DNA damage, the sliding clamp is covalently modified 2. DNA pol is released and translesion polymerase is loaded onto DNA 3. DNA is synthesised and covalent modifications are removed. 4. Translesion DNA pol is replaced by replicative DNA pol again
59
What is the double strand break repair that happens in G1?
Non-homologous end joining: Error prone Results in loss of nucleotides around break site Ku70/80 and DNA PKes facilitate end joining Ligase IV seals gaps
60
What is the double strand break repair that happens in S phase?
Homologous recombination: Error free repair that uses sister chromatids as a template
61
How is DNA damage initially detected?
1. ATM/ATR kinase associate with the site of DNA damage 2. Chk1/Chk2 kinase activates and phosphorylates p53 3. p53 dissociates from mdm2 and binds to a regulatory region of the p21 gene 4. This inactivates G1/S-CDK and S-CDK complexes, preventing the cell cycle progressing
62
What is xeroderma pigmentosum?
Autosomal recessive condition that increases skin cancer risk 2000 fold Associated with a defective NER pathway (UV damage)
63
How are cells with DNA damage studied?
Comet assay- electrophoresis to look at overall damage and find marks of DNA damage

Y2 Mol Bio (10 decks)

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