Cellular Genetics and Cell Cycle Flashcards by M Ahmed

Which is an example of an acrocentric chromosome?

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

Chromo 22

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A trisomy in which chromo causes Patau’s syndrome?

Chromo 13

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Between which weeks of pregnancy is amniocentesis usually carried out?

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

15-20

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

5’ end of lagging strand

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Which of these antiobiotics interferes with prokarytic transcription?

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

Rifamycin

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

CCR5 chemokine receptor (co-receptor for HIV)

Loss of 32bp in CCR5

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What genotype can affect the metabolism of drugs?

Cytochrome P450 (CYP2D6)

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HER2 defintion and what it can cause?

Human Epidermal Growth Factor Receptor

30% of breast cancer caused by overexpression

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What drug blocks activity of HER2 and what is it?

Trastuzumab (Herceptin)

Monoclonal antibody

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

Giemsa stain

binds to high amounts of adenine-thymine bonding

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What 3 things is the human chromosome characterised by?

Location of centromere
G-banding
Size

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What are the 3 types of chromosome shapes?

Metacentric
Subcentric
Acrocentric

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

4 sperm cells

1 egg cells

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What are the 3 parts of the Y chromosome?

Pseudoautosomal region
Sex Determining Region
Male Specific Region

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What is aneuploidy and how is it caused?

Irregular number of chromosomes

Non-disjunction during meiosis (oogenesis)

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What chromosome is Down’s syndrome associated with?

Extra copy of chromosome 21

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What chromosome is Edward’s syndrome associated with?

Extra copy of chromosome 18

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

130 days

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What is the main abnormality in Edward’s syndrome?

Intestines protruding outside body

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What are the sex chromosomes in Klinefelter Syndrome?

XXY

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What are the sex chromosomes in Turner Syndrome?

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What is amenorrhea?

Absence of menstruation

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What is the risk of miscarriage in amniocentosis?

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What are the 2 Mendelian laws?

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

508

What number chromosome of CFTR gene on?

Chromosome 7

What is an example of an autosomal recessive disease?

Cystic Fibrosis

What is an example of an autosomal dominant disease?

Huntingdon's disease

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

Haemophilic A

What causes Haemophilic A?

Mutation in gene for blood clotting factor VIII on X chromosome

What is a phage/bacteriophage?

Virus that infects bacteria

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

Sulphur-35

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

Phosphorus-32

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

Guanine and adenine | Double rings, 9 carbons

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

Cytosine and Thymine | Single ring, 6 carbons

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

Carbon 1

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

1.1%

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

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

44%

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

45%

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

6.6%

LINES definition?

Long Interspersed Elements

SINES definition?

Short Interspersed Elements

What is heterochromatin composed of?

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

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

``` Xic region (inactivation centre) Xist gene ```

What is anhidrotic ectodermal dysplasia?

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

What does mutation in miRNA-96 cause?

Hereditary progressive hearing loss

What does the mitochondrial circular genome encode?

13 polypeptides, rRNA, tRNA

Does mitochondrial circular DNA contain introns?

MELAS definition?

Myopathy, Encephalopathy, Lactic Acidosis, Stroke-like episodes

LHON definition?

Leber's Hereditary Optic Neuropathy

Definition of Matrilineal?

X follow autosomal/sex-linked inheritance patterns

What is the function of topoisomerase?

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

What direction is DNA synthesised?

5' to 3'

Can DNA polymerase initiate DNA synthesis?

Can RNA polymerase initiate RNA synthesis?

Yes

What is the lagging strand of DNA made up of?

Okazaki fragments

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

5' to 3' | Extends 3' OH ends

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

Removes wrong nucleotides added by DNA polymerase | DNA polymerase then adds correct one

How many replication origins in: a) eukaryotes b) prokaryotes

a) Multiple | b) 1

What is the end replication paradox?

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

What are telomeres and what do they consist of?

Caps at end of DNA, preventing loss of information | Hundreds of 5' TTAGGG 3', so when DNA shortens this is lost instead

What enzyme catalyses formation of telomeres?

Telomerase

What cells is telomerase active in?

Cells that give rise to gametes and stem cells

What type of protein is formed with a nonsense mutation?

Trunkated protein (stop codon expressed early)

What are microsateilites?

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

What causes Cri du Chat syndrome?

Deletion at the end of chromosome 5

What causes chronic myelogenous leukaemia (CML)?

Pieces of chromosome 9 and 12 translocate

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

UV-B | Induces chem bonds between adjacent thymines - thymine dimers

NER defintion?

Nucleotide Excision Repair

What is angiogenesis?

Formation of new blood vessels

What is metastasis?

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

What are the 3 stages in prokaryotic RNA Transcription?

Initiation, Elongation, Termination

What is capping?

Formation of 7-methylguanosine cap at 5' end

What is polyadenylation?

Addition of a tail to 3' end of mRNA | Adds 50-250 adenosine residues

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

Unmethylated cytosine | Acetylated histones

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

Methylated cytosine | Deacetylated histones

What causes Rett syndrome?

X-linked dominant disorder | Mutation in methyl CpG binding protein 2 (MECP2)

What are the 3 stop codons?

UAA, UAG, UGA

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

AUG, Methionine

What is wobble pairing and where does it occur?

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

What subunits make up the 70S ribosome?

50S and 30S

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

Exit, Site acceptor, polymerisation

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

Shine-Dalgarno

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

Ethidium bromide

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

Plasmids

What is an important feature of dideoxynucleotides (ddNTPs)?

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

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

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

What is DNA polymorphism?

Neutral variations in DNA sequencing

SNPs?

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

Haplotypes?

Series of SNP alleles along a single chromosome

What causes ALS?

Hexanucleotide repeat on chromsome 19 in gene C9orf72 | Repeat of GGGGCC, 100 repeats increases risk

5 requirements of Hardy-Weinburg principle?

``` Large population No migration No new mutation No selection Random mating ```

What does the ABO gene encode?

Glucosyl transferase enzyme

What is epigenetics?

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

What amino acid is lost in cystic fibrosis?

Phenylalanine

What causes psoriasis?

Excessive keratinocyte proliferation and immune cell activations

During DNA replication, what enzyme adds complementary bases?

DNA polymerase

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

Tryptophan (UGG)

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

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

How does chloramphenicol work?

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

How does tetracycline work?

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

How does rifamycin work?

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

How does puromycin work?

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

How do these chemicals affect nitrogenous bases? a) Nitrous acid b) Alkylating agents c) Free radicals

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

What is cDNA?

DNA copy of mRNA made using reverse transcriptase

Cellular Genetics and Cell Cycle Flashcards

(106 cards)