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BIO2036 Molecular Evolution > Molecular basis of biology and evolution > Flashcards

Molecular basis of biology and evolution Flashcards

1
Q

What makes DNA ideal for the long-term storage of genetic code data?

A

It is a durable, double-stranded polymer

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2
Q

Describe how the strands are ordered in DNA

A

With a 3’-OH and a 5’-PO4 on the sugar-phosphate backbone that run in opposite directions on the 2 strands

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3
Q

What are the 4 nucleotide bases?

A

Adenine
Thymine
Guanine
Cytosine

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4
Q

What is Watson-Crick base pairing?

A

A-T

C-G

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5
Q

Why must nucleotides be Watson-Crick base-paired?

A

The double-strand will be disrupted otherwise

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6
Q

What are purines?

A

Heavy nucleotides with 2 rings

A and G

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7
Q

What are pyrimidines?

A

Light nucleotides with 1 ring

T and C

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8
Q

Why is one strand from the double-strand always heavier than the other?

A

Due to different purine/pyrimidine composition

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9
Q

Which base pair is stronger?

A

G and C as they have 3 hydrogen bonds compared to A and T’s 2

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10
Q

During DNA replication, which end are new nucleotides added on to?

A

3’

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11
Q

Which direction is DNA replication carried out in?

A

5’-3’

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12
Q

At what speed is DNA elongation in bacteria?

A

500 bases s^-1

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13
Q

At what speed is DNA elongation in vertebrates?

A

50 bases s^-1

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14
Q

What is semi-conservative replication?

A

The new DNA molecule contains one new strand and one newly synthesised strand

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15
Q

What enzyme catalyses the bonding of the nucleotide to the sugar-phosphate backbone?

A

DNA polymerase

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16
Q

What nucleotide replaces thymine during transcription?

A

Uracil

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17
Q

Describe translation?

A

tRNAs bind specifically to the mRNA and the ribosome catalyses the binding of the amino acid to the polypeptide being synthesised

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18
Q

In which direction is the protein-coding segment of a gene written?

A

5’-3’

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19
Q

How are some codons degenerate?

A

There is some non-specificity in the third codon of the tRNA molecule thus some triplet codons will code for the same amino acid

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20
Q

What are some other names for the strand that goes in the 5’-3’ direction?

A

Plus (+) strand
Coding strand
Sense strand
Non-template strand

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21
Q

What are some other names for the strand that goes in the 3’-5’ direction?

A

Minus (-) strand
Non-coding strand
Antisense strand
Template strand

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22
Q

What strand does the forward primer bind to?

A

The template strand (-) and bases are added in the 5’-3’ direction (downstream)

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23
Q

What strand does the reverse primer bind to?

A

The non-template strand (+) and bases are added in the 5’-3’ direction (upstream)

24
Q

Describe the denaturing step of PCR

A

Temperature 94-96 degrees Celcius

Weak H bonds between nucleotide bases are broken at high temperatures

25
Q

Describe the annealing step of PCR

A

45-55 degrees Celcius

Primers anneal

26
Q

Describe the elongation step of PCR

A

75-80 degrees Celcius

Taq polymerase catalyses the addition of nucleotides to the 3’ end of the primers to create a new amplicon (DNA strand)

27
Q

How much of the human genome is made up of protein-coding exons?

A

~1.5%

28
Q

What are introns?

A

Originally thought of as junk DNA or remnants of protein domains that had become inactivated or retrovirus that had become inactivated but not eliminated
However, the splicosome and snRNAs are involved in splicing out the introns after transcription

29
Q

What are pseudogenes?

A

Non-functional coding regions where mutations made the gene product inactive or non-functional

30
Q

Why are DNA and amino acid sequences better for phylogenetic construction than morphology?

A

DNA and amino acid sequences are strictly heritable and are not influenced by the environment or aging and development
Molecular characteristics evolve at a more regular rate than morphological characters
Allow quantitative statistical analysis
There are more molecular characteristics than morphological ones

31
Q

What is the central dogma?

A

Information flows from DNA to RNA to protein

32
Q

What are the main vehicles for reverse transcriptase activity?

A

Retrotransposons

33
Q

How do RNA viruses replicate their RNA?

A

Using RNA dependant RNA polymerase

34
Q

What are RNA dependant RNA polymerases used in eukaryotes for?

A

Gene silencing, interference, and miRNA replication

35
Q

How does the secondary structure of proteins form?

A

Spontaneously due to the arrangement of interacting amino acids

36
Q

How do the tertiary and quaternary structures of proteins form?

A

Through helper proteins such as chaperones in order to fold correctly

37
Q

What are the 2 major types of mutations?

A

Point and segment

38
Q

Describe point mutations

A

A single base/base-pair substitution

39
Q

Where do point mutations most commonly occur?

A

By mispairing during DNA replication

40
Q

What percentage of point mutations cause missense changes to amino acid sequences?

A

~71%

41
Q

Why is there a higher chance that a synonymous mutation will occur in the 3rd base of a triplet codon?

A

Due to the degeneracy of the genetic code

42
Q

What is a single nucleotide polymorphism?

A

A substitution of a single nucleotide at a specific position in the genome that is present in a sufficiently large fraction of the population.

43
Q

What are some diseases that single nucleotide polymorphisms cause?

A

Sickle-cell anaemia

Cystic fibrosis

44
Q

What are the 3 types of segmental mutations?

A

Recombination
Indel
Inversion

45
Q

Describe recombination mutations

A

Occurs commonly during chromosomal cross-over during meiosis and also during insertion of retroviral sequences where short target sequences are replaced by longer retroviral sequences and retrotransposons

46
Q

Describe indel mutations

A

Could be either an insertion or a deletion

Are often fatal in coding regions as 2/3 will cause a frameshift mutation

47
Q

Describe unequal crossing over

A

Results in the deletion of a segment of the DNA in one chromosome (which will likely not survive) and insertion into another

48
Q

Describe inversion mutations

A

Can occur by intrachromosomal crossing over

49
Q

What base pairs will mutate more rapidly than others>

A

C and G

50
Q

What are transitions?

A

Purine:purine and pyrimidine:pyrimidine

51
Q

What are transversions?

A

Purine:pyrimidine

52
Q

Which out of transitions and transversions are more likely to mutate?

A

Transitions

53
Q

What is a synonymous mutation?

A

The evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified.

54
Q

What is more likely to occur, missense or synonymous mutations?

A

Missense

55
Q

What is a missense mutation?

A

A point mutation in which a single nucleotide change results in a codon that codes for a different amino acid.

BIO2036 Molecular Evolution (7 decks)

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