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FBS1 > Cellular Genetics and Cell Cycle > Flashcards

Cellular Genetics and Cell Cycle Flashcards

1
Q

Which is an example of an acrocentric chromosome?

a) chromo 3
b) chromo 17
c) chromo 22
d) chromo 7

A

Chromo 22

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2
Q

A trisomy in which chromo causes Patau’s syndrome?

A

Chromo 13

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3
Q

Between which weeks of pregnancy is amniocentesis usually carried out?

a) 15-20
b) 10-15
c) 25-30
d) 20-25

A

15-20

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4
Q

Also known as replication paradox, DNA replication results in the loss of a segment of DNA from which end?

A

5’ end of lagging strand

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5
Q

Which of these antiobiotics interferes with prokarytic transcription?

a) Rifamycin
b) Streptomycin
c) Chloramphenicol
d) Eryrthromycin

A

Rifamycin

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6
Q

What receptor do some people not have that makes them immune to infection by HIV-1 and what causes it?

A

CCR5 chemokine receptor (co-receptor for HIV)

Loss of 32bp in CCR5

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7
Q

What genotype can affect the metabolism of drugs?

A

Cytochrome P450 (CYP2D6)

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8
Q

HER2 defintion and what it can cause?

A

Human Epidermal Growth Factor Receptor

30% of breast cancer caused by overexpression

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9
Q

What drug blocks activity of HER2 and what is it?

A

Trastuzumab (Herceptin)

Monoclonal antibody

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10
Q

What is the stain used in G banding and what does it stain?

A

Giemsa stain

binds to high amounts of adenine-thymine bonding

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11
Q

What 3 things is the human chromosome characterised by?

A

Location of centromere
G-banding
Size

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12
Q

What are the 3 types of chromosome shapes?

A

Metacentric
Subcentric
Acrocentric

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13
Q

In meiosis, how many sperm cells are formed and how many egg cells are formed?

A

4 sperm cells

1 egg cells

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14
Q

What are the 3 parts of the Y chromosome?

A

Pseudoautosomal region
Sex Determining Region
Male Specific Region

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15
Q

What is aneuploidy and how is it caused?

A

Irregular number of chromosomes

Non-disjunction during meiosis (oogenesis)

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16
Q

What chromosome is Down’s syndrome associated with?

A

Extra copy of chromosome 21

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17
Q

What chromosome is Edward’s syndrome associated with?

A

Extra copy of chromosome 18

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18
Q

What is the mean survival time in Patau’s syndrome?

A

130 days

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19
Q

What is the main abnormality in Edward’s syndrome?

A

Intestines protruding outside body

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20
Q

What are the sex chromosomes in Klinefelter Syndrome?

A

XXY

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21
Q

What are the sex chromosomes in Turner Syndrome?

A

X

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22
Q

What is amenorrhea?

A

Absence of menstruation

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23
Q

What is the risk of miscarriage in amniocentosis?

A

1%

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24
Q

What are the 2 Mendelian laws?

A

Every individual possesses a pair of alleles for a given trait, one of which is passed onto offspring
Genes for different traits assort independantly to each other - unless they’re linked

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25
Q

At what codon position are there the most mutant alleles for cystic fibrosis in Northern European population?

A

508

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26
Q

What number chromosome of CFTR gene on?

A

Chromosome 7

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27
Q

What is an example of an autosomal recessive disease?

A

Cystic Fibrosis

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28
Q

What is an example of an autosomal dominant disease?

A

Huntingdon’s disease

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29
Q

What is an example of an X-linked recessive disease?

A

Haemophilic A

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30
Q

What causes Haemophilic A?

A

Mutation in gene for blood clotting factor VIII on X chromosome

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31
Q

What is a phage/bacteriophage?

A

Virus that infects bacteria

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32
Q

What can only proteins be labelled with (but not DNA)?

A

Sulphur-35

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33
Q

What can only DNA be labelled with (but not proteins)?

A

Phosphorus-32

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34
Q

What are the purines in DNA and what is distinct about them?

A

Guanine and adenine

Double rings, 9 carbons

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35
Q

What are the pyramidines in DNA and what is distinct about them?

A

Cytosine and Thymine

Single ring, 6 carbons

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36
Q

At what carbon position does the deoxyribose in DNA react with a base?

A

Carbon 1

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37
Q

What percentage of the human genome encodes protein (approx)?

A

1.1%

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38
Q

What percentage of the human genome are regulatory regions (approx)?

A

4%

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39
Q

What percentage of the human genome are other unique sequences, including introns (approx)?

A

44%

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40
Q

What percentage of the human genome is transposon based repeats (approx)?

A

45%

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41
Q

What percentage of the human genome is heterochromatin (approx)?

A

6.6%

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42
Q

LINES definition?

A

Long Interspersed Elements

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43
Q

SINES definition?

A

Short Interspersed Elements

44
Q

What is heterochromatin composed of?

A

Long arrays of high copy number tandem repeated DNA sequences - satellite DNA

45
Q

What is the region in the middle of the X chromosome called and what does it contain?

A 
Xic region (inactivation centre)
Xist gene
46
Q

What is anhidrotic ectodermal dysplasia?

A

Defective sweat glands

Heterozygous females show random patterns of tissue with/without sweat glands

47
Q

What does mutation in miRNA-96 cause?

A

Hereditary progressive hearing loss

48
Q

What does the mitochondrial circular genome encode?

A

13 polypeptides, rRNA, tRNA

49
Q

Does mitochondrial circular DNA contain introns?

A

No

50
Q

MELAS definition?

A

Myopathy, Encephalopathy, Lactic Acidosis, Stroke-like episodes

51
Q

LHON definition?

A

Leber’s Hereditary Optic Neuropathy

52
Q

Definition of Matrilineal?

A

X follow autosomal/sex-linked inheritance patterns

53
Q

What is the function of topoisomerase?

A

Breaks a phosphodiester bond in one of the parental strands ahead of the replication fork
Releases supercoils in DNA

54
Q

What direction is DNA synthesised?

A

5’ to 3’

55
Q

Can DNA polymerase initiate DNA synthesis?

A

No

56
Q

Can RNA polymerase initiate RNA synthesis?

A

Yes

57
Q

What is the lagging strand of DNA made up of?

A

Okazaki fragments

58
Q

What direction does DNA polymerase extend DNA and from what part of the nucleotide?

A

5’ to 3’

Extends 3’ OH ends

59
Q

What is the function of the 3’-5’ exonuclease?

A

Removes wrong nucleotides added by DNA polymerase

DNA polymerase then adds correct one

60
Q

How many replication origins in:

a) eukaryotes
b) prokaryotes

A

a) Multiple

b) 1

61
Q

What is the end replication paradox?

A

DNA at very end of chromosome cannot be fully copied (as chromosome is linear), resulting in gradual shortening of chromosome

62
Q

What are telomeres and what do they consist of?

A

Caps at end of DNA, preventing loss of information

Hundreds of 5’ TTAGGG 3’, so when DNA shortens this is lost instead

63
Q

What enzyme catalyses formation of telomeres?

A

Telomerase

64
Q

What cells is telomerase active in?

A

Cells that give rise to gametes and stem cells

65
Q

What type of protein is formed with a nonsense mutation?

A

Trunkated protein (stop codon expressed early)

66
Q

What are microsateilites?

A

Short set of repeated DNA sequence at a particular locus on a chromosome

67
Q

What causes Cri du Chat syndrome?

A

Deletion at the end of chromosome 5

68
Q

What causes chronic myelogenous leukaemia (CML)?

A

Pieces of chromosome 9 and 12 translocate

69
Q

What type of UV light is the major mutagenic factor and what does it do?

A

UV-B

Induces chem bonds between adjacent thymines - thymine dimers

70
Q

NER defintion?

A

Nucleotide Excision Repair

71
Q

What is angiogenesis?

A

Formation of new blood vessels

72
Q

What is metastasis?

A

Developement of a secondary malignant growth at a distance from the primary site of cancer

73
Q

What are the 3 stages in prokaryotic RNA Transcription?

A

Initiation, Elongation, Termination

74
Q

What is capping?

A

Formation of 7-methylguanosine cap at 5’ end

75
Q

What is polyadenylation?

A

Addition of a tail to 3’ end of mRNA

Adds 50-250 adenosine residues

76
Q

What are the features of chromatin when a gene is switched on?

A

Unmethylated cytosine

Acetylated histones

77
Q

What are the features of chromatin when a gene is switched off?

A

Methylated cytosine

Deacetylated histones

78
Q

What causes Rett syndrome?

A

X-linked dominant disorder

Mutation in methyl CpG binding protein 2 (MECP2)

79
Q

What are the 3 stop codons?

A

UAA, UAG, UGA

80
Q

What is the initiation codon and the amino acid it codes for?

A

AUG, Methionine

81
Q

What is wobble pairing and where does it occur?

A

Pairing between 2 nucleotides that don’t follow Watson-Crick base pair rules
tRNA

82
Q

What subunits make up the 70S ribosome?

A

50S and 30S

83
Q

What are the 3 areas in the mRNA binding site of ribosomes?

A

Exit, Site acceptor, polymerisation

84
Q

What sequence in prokaryotes helps find the start codon for transcription?

A

Shine-Dalgarno

85
Q

What is added to the gel in agarose gel electrophoresis to visualise DNA?

A

Ethidium bromide

86
Q

What vector is used to carry DNA fragments into host cells?

A

Plasmids

87
Q

What is an important feature of dideoxynucleotides (ddNTPs)?

A

Don’t have -OH on 3’ carbon so DNA polymerase x further incorporate nucleotides

88
Q

What are the 3 steps in PCR and the approximate temperature for each?

A

Denaturation - 95C
Primer annealing - 45-68C
Extension - 72C

89
Q

What is DNA polymorphism?

A

Neutral variations in DNA sequencing

90
Q

SNPs?

A

Single Nucleotide Polymorphisms - most abundant type of polymorphism in human genome

91
Q

Haplotypes?

A

Series of SNP alleles along a single chromosome

92
Q

What causes ALS?

A

Hexanucleotide repeat on chromsome 19 in gene C9orf72

Repeat of GGGGCC, 100 repeats increases risk

93
Q

5 requirements of Hardy-Weinburg principle?

A 
Large population
No migration
No new mutation
No selection
Random mating
94
Q

What does the ABO gene encode?

A

Glucosyl transferase enzyme

95
Q

What is epigenetics?

A

Study of heritable changes in gene expression and doesn’t involve changes to underlying DNA sequences

96
Q

What amino acid is lost in cystic fibrosis?

A

Phenylalanine

97
Q

What causes psoriasis?

A

Excessive keratinocyte proliferation and immune cell activations

98
Q

During DNA replication, what enzyme adds complementary bases?

A

DNA polymerase

99
Q

Other than methionine, what other AA has a single unique codon?

A

Tryptophan (UGG)

100
Q

How does the toxin of diphtheria work and what does the anti-toxin affect?

A

Covalently modifies elongation factor required in translocation step of protein synthesis, inhibits synthesis of new proteins + causes tissue damage
Reacts with free plasma form of toxin, X intra cellular bound form

101
Q

How does chloramphenicol work?

A

Inhibits peptidyl transferase activity of 50S ribosomal subunit (elongation stage)

102
Q

How does tetracycline work?

A

Inhibits attachment of aminoacyl t-RNA to 30S ribosomal subunit (initiation stage)

103
Q

How does rifamycin work?

A

Binds to RNA polymerase + prevents copying of DNA to mRNA (transcription)

104
Q

How does puromycin work?

A

Resembles prt of structure of an amino acyl t-RNA + binds to large ribosomal subunit
Causes premature termination of growing polypeptide chain (termination stage)

105
Q

How do these chemicals affect nitrogenous bases?

a) Nitrous acid
b) Alkylating agents
c) Free radicals

A

a) Cytosine ==> uracil
b) Guanine modifications
c) Strand breaks

106
Q

What is cDNA?

A

DNA copy of mRNA made using reverse transcriptase

FBS1 (5 decks)

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