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Molecular Genetics Flashcards

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1
Q

in eukaryotic cells, transcription cannot begin until

A

several transcription factors have bound to the promoter

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2
Q

Which of the following is true of a codon?
a. never codes for the same amino acid as another
b. can code for more than one amino acid
c. it can be in either RNA or DNA
d. it is the basic unit of protein structure

A

C

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3
Q

the anticodon of a particular tRNA molecule is complementary to what

A

complementary to a corresponding mRNA molecule

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4
Q

which of the following is true of RNA processing?
a. exons are cut our before mRNA leaves the nucleus
b. nucleotides are added at both ends of the RNA
c. Ribozymes may function in the addition of a 5’ cap
d. DNA splicing adds poly-A-tail

A

B.

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5
Q

Which of mutations would be most likely to have a harmful effect on an organism

A

A single nucleotide insertion downstream of, and close to, the start of the coding sequence.

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6
Q

could the coupling of processes in bacterial cell replication occur in a human cell?

A

No, transcription and translation are separated in space and time in a eukaryotic cell, as a result of the nuclear membrane

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7
Q

mRNA function

A

carries genetic information specifying amino acid sequences of polypeptides from DNA to ribosomes

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8
Q

tRNA function

A

serves as a translator molecule in protein synthesis; translates mRNA codons into amino acids

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9
Q

rRNA function

A

in a ribosome, plays a structural role. as a ribozyme, plays a catalytic role

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10
Q

primary transcript funciton

A

is a precursor to mRNA, rRNA, or tRNA, before being processed; some intron RNA acts as an enzyme, catalysing its own splicing.

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11
Q

small RNAs in the spliceosome function

A

plays structural and catalytic roles in spliceosones, the cmplexes made from RNA and proteins that splice pre-mRNA.

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12
Q

provide evolutionary example for why codons for amino acids are similar

A

this is due to evolutionary genetic advantage that means by having similar codons, the effect of single point mutations that occur often during replication is minimised. the similarity is due to the robustness of the universal genetic code against mutations.

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13
Q

why would a human blood cell die when inserted in a bacterial cell?

A

this is due to the different methods of RNA processing. most human cells have introns and bacterial cells to not have the machinery to cut out introns and splice together RNA, therefore the proteins are likely non functional.

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14
Q

What can changes to the genotype result in?

A

Changes to phenotype through sequence of bases in RNA or amino acids in proteins.

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15
Q

What roles can proteins play in the phenotype?

A
  • Make structures
  • Act as enzymes
  • Act as signals
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16
Q

How do different alleles affect proteins?

A

Different alleles can produce different proteins.

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17
Q

What is the relationship between proteins and phenotypes?

A

Different proteins can produce different phenotypes.

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18
Q

What is the primary sequence of a protein?

A

Amino acid sequence.

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19
Q

What does the primary sequence specify?

A

The way it folds into secondary and tertiary structures.

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20
Q

What is transcription?

A

The process of converting DNA to RNA.

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21
Q

What are the similarities between RNA and DNA?

A
  • Both are nucleic acids
  • Have sugar phosphate backbone
  • Backbone carries series of 4 bases
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22
Q

What is a key difference between RNA and DNA?

A

RNA is often single stranded, while DNA is double stranded.

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23
Q

What is a promoter?

A

A special DNA sequence where RNA polymerase binds to start transcription.

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24
Q

What happens during the elongation phase of transcription?

A

Addition of complementary rNTPs.

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25
What occurs during termination of transcription?
Release of RNA polymerase and completed RNA from the DNA template.
26
What is the significance of mRNA degradation?
It allows genes to be turned on and off, making cells nimble and responsive.
27
How does the lac operon respond to the presence of lactose?
Lactose binds to the repressor, allowing transcription of lactase genes.
28
What is a feedback loop in the context of the lac operon?
As soon as lactose is in the system, it binds to the repressor protein, allowing transcription to occur.
29
What is the role of the repressor protein in the lac operon?
It prevents RNA polymerase from binding to the operator, blocking transcription.
30
What type of mutations can affect evolution?
Point mutations.
31
True or False: Phenotype can be predicted solely from genotype.
False.
32
Fill in the blank: DNA is a perfect information storage because it is _______.
Stable, copyable, inert.
33
What must happen for DNA information to be used?
It needs to get out of DNA and be taken to where it is needed.
34
What is a significant characteristic of RNA compared to DNA?
RNA is more likely to break down due to being single-stranded.
35
redundancy of the code
What feature of the genetic code allows for the same amino acid to be specified by multiple codons?
36
What does the universality of the genetic code suggest about all living things?
They have a single common ancestor
37
What type of bonding makes the interaction between a codon and tRNA anticodon specific?
Hydrogen bonding
38
What are the three sites in the ribosome?
* P SITE * A SITE * E SITE
39
What occurs during the initiation phase of protein synthesis?
Assembly of the ribosome on the mRNA at the start codon
40
What is the start codon recognized by during initiation?
tRNA (AUG)
41
What are the three steps involved in the elongation phase of translation?
* Entry of the right tRNA * Formation of peptide bond * Translocation
42
What signifies the termination of protein synthesis?
Encountering a stop codon
43
What catalyzes the release of the completed protein during termination?
Release factors
44
What is the primary structure of a protein?
A string of amino acids in the correct order
45
What two secondary structures can proteins form?
* A-helix * B-pleated sheet
46
What can changes in a gene sequence affect?
The sequence of amino acids in the polypeptide
47
Where does translation occur in prokaryotes?
In the cytosol
48
Where does transcription occur in eukaryotes?
In the nucleus
49
What is the role of ribosomal proteins in translation?
To make use of GTP
50
example of gene sequence mutation and effect on protein
high altitude species: mutation in haemoglobin gene sequence changes amino acid sequence (primary structure) changes protein folding (secondary structure) changes the way subunits come together better oxygen uptake
51
What determines what proteins are currently being built in a cell?
Which genes are being transcribed
52
What is the effect of changing the base sequence of a protein-coding gene?
It changes the amino acid sequence of a protein, which can change the function of the protein by altering the structure (of paired sections or loops) and functions
53
What is a point mutation?
A single base change in the DNA sequence of a gene.
54
What is a silent mutation?
The base change does not result in a protein change.
55
What is a missense mutation?
A single amino acid is changed due to a base change.
56
What is a nonsense mutation?
An amino acid codon is changed to a stop codon.
57
What is a frameshift mutation?
Deletion or addition of one or two bases changes the reading frame.
58
How can mutations in the melanin pathway affect hair color?
A missense mutation can change one base in the gene, leading to blonde hair.
59
What is the result of a nonsense mutation in the TYRP1 gene?
It changes TAT (tyrosine) to TAG (stop), producing a truncated protein that doesn’t function.
60
What is the effect of a frameshift mutation in the MDR1 gene?
It causes translation to go awry, leading to sensitivity to ivermectin in collies.
61
the base sequence in the gene specifies ....
the primary amino acid sequence
62
What are the two main sources of point mutations?
* Replication errors * DNA damage
63
What happens during the base selection step in DNA replication?
Correct base causes conformational change in enzymes, engaging polymerase active sites.
64
What is proofreading in DNA replication?
An accurate process where wrong bases joined to the growing strand are corrected.
65
What is the consequence of incorrect base pairing during DNA replication?
It distorts the DNA helix and can lead to errors.
66
Why do retroviruses have high evolution rates?
They have no proofreading, generating a lot of variation.
67
What is post-replication repair?
A process where repair machinery detects and corrects incorrect bases after replication.
68
What happens if DNA repair machinery fails?
It can lead to cell death and the mutation does not enter the gene pool.
69
What is the error rate of DNA replication in humans?
Less than one in a billion bases copied.
70
In which gametes do mutations mostly occur?
In sperm, due to more cell divisions as males age.
71
What are some examples of DNA damage caused by chemicals?
* Changes bases so they don’t pair the same way * Replaces normal bases (base analogues) * Fits between bases (intercalating agents) * Alters existing bases (deamination)
72
What type of mutation can UV light induce?
It can cause two T bases to bond with each other, preventing proper base pairing.
73
types of repair and their functions: What is photoreactivation?
1. photo-reactivation: A repair mechanism that directly reverses DNA damage. 2. excision repair: A method that removes and replaces damaged DNA strands. 3. recombination repair: using a homologous strand to replace damaged DNA 4. SOS response: cell attempts any possible repair to survive, error prone
74
What is a mutation?
A permanent change to the base sequence that will be copied to all DNA made from that strand.
75
How does mutation contribute to evolution?
It creates genetic variation that can be acted upon by natural selection.
76
similarites and differences for the synthesis of leading and lagging strands
Similarities: DNA polymerase adds onto the 3' end of an RNA primer synthesised by primase, synthesising DNA in the 5' - 3' direction. Differences: because the parental strands are parallel, DNA synthesis only proceeds continuously on the leading strand. On the leading strand, synthesis proceeds in the direction of the replication fork. The lagging strand is synthesised in sections in the direction away from the replication fork as a series of Okazaki fragments later joined by dna ligase. Although both strands are synthesised at the same rate, synthesis of the lagging strand is slightly delayed as it must wait until an available stretch of DNA opens.
77
what is the basis for the difference of how leading vs lagging strands are synthesised
C. DNA polymerase can only join new nucleotides to the 3' end of a pre-existing strand, and the strands are antiparallel
78

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