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molecular genetics > year one revision > Flashcards

year one revision Flashcards

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Biology 101 flashcards
1
Q

what is a nucleoside?

A

base and sugar

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2
Q

what is a nucleotide?

A

nucleoside and phosphate group

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3
Q

DNA pentose sugar

A

deoxyribose

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4
Q

RNA pentose sugar

A

ribose

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5
Q

bases structure

A

consists of heterocyclic rings of carbon and nitrogen atoms.

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6
Q

DNA and RNA basic structure

A

phosphate - pentose sugar - nitrogenous base

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7
Q

how many rings do purines have?

A

two interlocked rings

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8
Q

how many rings do pyrimidines have?

A

single ring

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9
Q

which bases are purines?

A

adenine and guanine

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10
Q

which bases are pyrimidines?

A

cytosine, thymine and uracil

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11
Q

what are the common bases in DNA and RNA?

A

adenine, cytosine and guanine

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12
Q

what base is present in DNA but not RNA?

A

thymine

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13
Q

what base is present in RNA but not DNA?

A

uracil

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14
Q

what does uracil lack that is found in thymine?

A

5-methyl group

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15
Q

how is a base attached to a sugar?

A

covalently bonded by N-glycosidic bond

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16
Q

which form of DNA is most common?

A

B-DNA

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17
Q

A-DNA structure

A

right handed
pitch of 3.2nm
11 bases per turn

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18
Q

B-DNA structure

A

right handed
pitch of 3.4nm
10 bases per turn

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19
Q

Z-DNA structure

A

left handed
pitch of 4.5nm
12 bases per turn

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20
Q

codon definition

A

sequence of three nucleotides that correspond with a specific amino acid or stop signal

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21
Q

composition of bacterial genomes

A

single circular chromosome

considered haploid

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22
Q

plasmid definition

A

extra-chromosomal DNA, often found in the cytoplasm of a bacterial cell,which replicates independently

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23
Q

histone definition

A

small, basic proteins bound tightly to DNA

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24
Q

function of histones

A

structural support

involved in packaging

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25
Q

histone charge

A

positive

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26
Q

chromatin definition

A

DNA- protein complex

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27
Q

chromosome packaging at interphase

A

low packaging

28
Q

what does first level of DNA packaging involve?

A

periodic coiling of the double helix around histone proteins

29
Q

nucleosome definition

A

a length of DNA coiled around a core of histones

146 base pairs coiled arounf 8 histones

30
Q

how are adjacent nucleosomes connected?

A

by linker DNA ( can be as long as 114bp)

histone H1 binds to linker DNA close to the nucleosome

31
Q

euchromatin definition

A

loosely packaged DNA
can be transcribed
weak binding of histone H1

32
Q

heterochromatin

A

tightly packaged DNA
cannot be transcribed
strong binding of histone H1

33
Q

what must chromosomes conain in order to be copied and transmitted accurately?

A

a centromere
replication origins
telomeres

34
Q

chromosome packaging during metaphase

A

highly packaged so they do not get tangled during cell division

35
Q

linear size of chromosomes during metaphase

A

0.01% of the fully extended chromosomal DNA

36
Q

what enzyme causes DNA strands to unwind?

A

DNA helicase

37
Q

At what end are the nucleotides added the the DNA strand?

A

3’ end

38
Q

what happens to deoxynucleoside triphosphates before they are added to the DNA strand?

A

DNA polymerase cleaves the precursors between the alpha and beta phosphate groups creating deoxynucleoside monophosphate that can be added

39
Q

what does semi-conservative DNA replication mean?

A

each daughter duplex contains one strand from the original DNA duplex and one newly synthesised DNA strand

40
Q

what is the direction of growth on the leading strand?

A

5’ to 3’

41
Q

what is the direction of growth on the lagging strand?

A

3’ to 5’

42
Q

what is the most common secondary structure of RNA in a cell?

A

hairpin

43
Q

what does the hairpin RNA structure consist of?

A

stem and loop arrangement

RNA strand loops back and complementary bases pair forming the stem and leaves a small loop of unpaired bases

44
Q

how much of the total cellular RNA does rRNA make up?

A

80%

45
Q

what is rRNA

A

ribosomal RNA

46
Q

what is tRNA

A

transfer RNA

acts as an adapter molecule between the nucleotide sequence of the mRNA molecule and amino acid

47
Q

how much of the total cellular RNA does tRNA make up?`

A

15%

48
Q

how is mRNA modified in eukaryotes?

A

addition of 5’ cap
addition of 3’ polyadenyl tail
introns spliced by spliceosomes. only after this happens can the mature mRNA leave the nucleus

49
Q

why is a 5’ cap added to mRNA?

A

allows recognition by the ribosome

50
Q

how is a 5’ cap added to mRNA?

A

add a G to 5’ end which is then methylated

51
Q

why is a 3’ polyadenyl tail added to mRNA?

A

increases the half life and increases the efficiency of translation

52
Q

what enzyme adds the 3’ polyadenyl to mRNA?

A

poly (A) polymerase

53
Q

which RNA polymerase is responsible for transcribing all protein-coding genes in the nucleus?

A

RNA polymerase II

54
Q

which DNA strand is used as a template during transcription?

A

antisense strand

55
Q

what is the process of transcription?

A

DNA helicase unwinds the DNA locally as RNA polymerase advances
ribonucleoside triphosphate precursors are cleaved by the polymerase to form ribonucleoside monophosphates which are added on nucleotide as a time to the 3’ hydroxyl group of the previous nucleotide

56
Q

what are transcription factors and what do they do?

A

proteins which bind to the promoter and position and guide the RNA polymerase to help transcription proceed effectively

57
Q

what is the start codon?

A

AUG

58
Q

what are the stop codons?

A

UAG
UAA
UGA

59
Q

what is a point mutation

A

when a single base pair is altered

60
Q

what are the types of point mutation

A

substitution
deletion
addition

61
Q

what are the possible effects of point mutations

A

silent- no effect, the base change still encodes for the same amino acid
missense- the base change now encodes for a different amino acid
nonsense- the base change encodes for a stop codon

62
Q

what is an open reading frame?

A

section of DNA between a start and stop codon that is able to be translated
no overlaps and no gaps

63
Q

how many reading frames does double stranded DNA have?

A

6

64
Q

what does cDNA stand for?

A

complementary DNA

65
Q

what are exons?

A

protein coding regions

66
Q

what are introns?

A

non protein coding regions

molecular genetics (9 decks)

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