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Cels191 > Module 2 > Flashcards

Module 2 Flashcards

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1
Q

How are nucleotides joined

A

Condensation reactions

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2
Q

Formation of polynucleotide bonds

A

The hydroxyl group on the 3rd carbon of on nucleotide reacts with the phosphate group attached to the 5th carbon on another nucleotide

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3
Q

What directions are dna and rna strands synthesised

A

5’ to 3’

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4
Q

Genes may contain sequences that are

A
  • responsible for the regulation of the synthesis of RNA
  • produce RNA
  • responsible for further processing of the RNA
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5
Q

What direction does the coding strand run

A

5’ to 3’

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6
Q

mRNA synthesis

A

Catalysed by RNA pol 2, which has a primase function and can form phosphodiester bonds

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7
Q

Primase

A

An enzyme that has an active site that can bind 2 ribonucleotide triphosphates (dNTPs) and catalyse the formation of a phosphodiester bind to form a dinucleotide by providing a 3’ OH group for further dNTP addition

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8
Q

Initiation - transcription

A

Transcription factors bind to TATA box and other regions of the promoter, RNA pol 2 binds forming a transcriptional initiation complex. 2 DNA strands seperate, as RNA pol 2 recruits helical and RNA pol 2 starts mRNA synthesis

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9
Q

Topoisomerase 2

A

An enzyme that releases the tension (supercoil) that builds up ahead or RNA pol 2

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10
Q

Promoter region

A

DNA segment recognised by RNA pol to initiate transcription

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11
Q

mRNA processing

A
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12
Q

UTRs

A

Transcribed but not usually translated contain regulatory elements that influence on gene expression at transcriptional or translational levels

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13
Q

5’ UTR facilitates

A

The addition of 5’ g cap

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14
Q

3’ UTR facilitates

A

The addition of a poly a tail

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15
Q

5’ cap function

A

Prevents degradation, promote intron excision, and provides binding site for small ribosomal subunit

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16
Q

Poly a tail function

A

Prevents mRNA degradation, facilitates export of mRNA from nucleus

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17
Q

Stop codons

A

UAA UAG UGA

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18
Q

Start codon

A

AUG

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19
Q

tRNA structure

A

70-80 nucleotides, single stranded

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20
Q

What enzyme is involved in charging tRNA

A

Aminoacyl-tRNA synthetase

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21
Q

Anatomy of ribosome

A

E site -exit site p
P site - peptitidyl-tRNA binding site
A site- aminoacyl-tRNA binding site

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22
Q

Translation initiation

A

A initiator tRNA met binds to small ribosomal subunit, and identifies the 5’ g cap of mRNA and attaches to it and the small ribosomal subunit moves along until finds start codon, tRNA moves to p-site, large ribosomal subunit attaches

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23
Q

What stages of translation require energy

A

All require GTP

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24
Q

Elongation - translation

A

A charged tRNA with anticodon complementary to a site, lands in a site, the ribosome will break bond that binds amino acid to the tRNA in p-site and transfer the amino acid to the tRNA in a site forming a peptide bond, the ribosome moves 3 nucleotide down and the tRNA with growing chain moves to p site and the chain can exit through tunnel, uncharged tRNA enters e site and detaches and tRNA is expelled, new charged tRNA enters a site

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25
When is gtp used in elongation of translation
Binding of charged tRNA
26
Termination - translation
When ribosome reaches stop codon a protein called release factor enters a site, which breaks the bonds btw p site tRNA using water and the final amino acid causing polypeptide chain to detach from tRNA, the small and large ribosomal subunits dissociate from mRNA and each other
27
Where are the origins of replication and why
AT rich regions as there are only 2 bonds btw a and t therefore is easier to break apart
28
What direction is dna replication
Towards the replication fork
29
Primase
A type of RNA pol that makes RNA primers, which will act as a starting point for dna polymerase
30
What polymerase enzyme is used in DNA replication
DNA POL 3
31
What is ssbp and what are they used for
Single stranded binding protein, protect single strands of DNA from being degraded (as single strands are prone to degradation), and prevent strands from coming back together
32
Initiation of DNA replication
Primase makes RNA primers (6-10bp), DNA POL3 will use the 3’ hydroxyl group of RNA primer and add the next nucleotide, as it moves will kick the ssbp out of the way
33
DNA POL1
- RNase H endonuclease enzyme that recognises dna rna hybrids and degrades the rna part -and fills gap with DNA nucleotides (DNA polymerase)
34
DNA ligase
Joins newly synthesised Okazaki fragments together by creating phosphodiester bonds
35
What is needed to replicate dna
-DNA POL3 -PRIMASE -HELICASE -TOPOISOMERASE -SSBP -DNA POL1 -DNA LIGASE
36
Topoisomerase
Release tension generated by unwinding the dna helix by cutting and rejoining dna helix
37
How can DNA errors be repaired
During replication - exonuclease After replication - endonuclease
38
Repair DNA errors during replication
- DNA POL 3 has a proofreading mechanism (checks newly inserted against the template, and incorrect base is removed by the exonuclease activity of DNA pol 3
39
What direction does DNA POL 3 exonuclease activity occur
3’ to 5’
40
Endonuclease action
Endonuclease will identify incorrect base and remove a large number of bases, a type of DNA pol will use 3’ hydroxyl group to bind and fill gap and DNA ligase will join
41
What is cell division required for
Growth and development and tissue repair
42
Characteristics of g2
- nuclear envelope intact - two centrosomes form - chromosomes have not condensed
43
Non-disjunction
The failure of chromosomes to seperate during meiosis
44
Polyploidy
Possession of more then 2 complete chromosome sets
45
How might polyploidy arise
- may arise due to non-disjunction of all chromosomes in one gamete -failure of zygote to divide after replicating its chromosomes during interphase
46
Turner syndrome
Monosomy - one X chromosome
47
Klinefelter syndrome
Aneuploid for X chromosome (extra copy)
48
Trisomy 21
3 copies of chromosome 21 - Down syndrome
49
Familial Down syndrome
One parent a carrier of 14/21 translocation
50
Deletion
When a chromosome breaks, and a portion is lost - usually results in a loss of genes
51
Duplications
- when a chromosome is present more than once - may occur when a broken fragment reattaches as an extra segment to a sister/non-sister chromatid
52
Translocations
A section of chromosome attaches to a non-homologous chromosome
53
Inversion
When part of a chromosome is inverted within a chromosome
54
Dosage compensation
Process by which expression levels of sex linked genes are altered in one sex to offset a difference in sex chromosome number
55
What happens to an inactivated chromosome
It condenses into a Barr body
56
Barr body
A highly condensed structure that lies against the nuclear envelope in cells of females
57
Evidence of x inactivation
Calico cat, there are 2 diff alleles of the fur colour gene, only female cats can be calico
58
Polymorphic genes
Genes that have 2+ common alleles, (each allele must have a freq of at least 1%)
59
Incomplete dominance
Neither of the 2 traits fully masks the other resulting in blended/intermediate phenotypes
60
Codominance
Where both phenotypes exist side by side within organism
61
Polygenic traits
Phenotype controlled by many genes that have additive effects
62
Hardy Weinberg equation
p2+pa+pq+q2=1
63
What does q and p mean in the hardy Weinberg eq
P- freq of dominant allele Q- freq of recessive allel
64
Population
A localised group of individuals of the same species
65
Allele freq can change due to
Non-random mating (assortative or inbreeding) Random genetic drift Bottleneck effect Founder effect Gene flow/migration Mutation Natural selection
66
Types of natural selection
Disruptive, stabilising, directional
67
Directional natural selection
Favours one extreme
68
Stabilising natural selection
Most common phenotype favoured
69
Disruptive natural selection
Favouring extremes

Cels191 (2 decks)

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