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1 mtm > Lectures 11-20 > Flashcards

Lectures 11-20 Flashcards

1
Q

What makes the ribose groups of DNA and RNA different?

A

RNA has an -OH group at ribose C2 (making is less stable as it can be attacked by water)

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2
Q

What are spliced out?

A

introns

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3
Q

What are repeat elements used for?

A

Detecting polymorphisms

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4
Q

What are the building blocks for DNA synthesis?

A

Deoxynucleoside triphosphates

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5
Q

How many Pi groups are released when a phosphodiester bond is formed?

A

2

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6
Q

What is required for DNA Polymerase to work?

A

RNA primer (added via primase), which is later removed

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7
Q

How does a phosphodiester bond form?

Why is this significant?

A

The 3’ OH group on the RNA primer attacks the phosphate, releasing 2 Pi groups
This is why DNA replication is 5’ to 3’

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8
Q

What happens when there is a problem in DNA replication?

A

DNA polymerase goes back and checks the base, and may excise it

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9
Q

What are the two strands in the replication fork?

A

The leading and lagging strands

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10
Q

WHat does the lagging strand use to synthesise DNA in the correct direction?

A

RNA primers.
DNA Polym. 1 replaces DNA Polym 3. and forms a DNA strand from the RNA primer,.
DNA ligase forms a phosphodiester bond between the sections

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11
Q

How is DNA spliced?

A

RNA containts all the machinery on it, including a spliceosome, allowin splicing to occur contrascriptionally

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12
Q

What would you find in RIbosome small subunits?

A 
A sites (binding site for aminoacyl tRNA)
P sites (binding site for peptidyl tRNA)
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13
Q

What codes for stop?

A

UAA
UAG
UGA

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14
Q

What does AUG code for?

A

Methionine (START)

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15
Q

How many genes do mitochondria have?

A

37

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16
Q

Name one property of the transcriptome and proteom

A

They’re dynamic

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17
Q

What are VNTR’s

A

Variable number tandem repeats, blockes of repeated sequences

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18
Q

What kinds of satellite DNA are there?

A

Micro (smaller, 2-6 bases) and mini (10-60 bases)

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19
Q

What is a telomere?

A

allow replication to tips of chromosomes, and protect chromosomes from fusing to one-another

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20
Q

What are centromeres for?

A

segregation in cell division

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21
Q

What are the two types of chromatin?

A

Euchromatin is uncoiled, where heterochromatin in densely packed

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22
Q

What are spindles?

A

focuses of microtubules (tw o per cell)

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23
Q

What are the different forms of microtubules?

A

interpolar microtubules elongate and repel spindles
Kinetochore microtubules are attached to the kinetochore
Aster fibres

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24
Q

What splits cells in cytokinesis?

A

a contractile ring of actin and myosin filaments

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25
Q

Give two reasons as to why meiosis is necessary

A

reduction division

re-assortment of genes

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26
Q

What kinds of non-harmful polymorphisms are there?

A

variant is in non-functional DNA, in gene but doesn’t change amino acid, or amino acid change doesn’t change protein function

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27
Q

How can large blocks of DNA be examined?

A

Microarray analysis or flourescence in situ hybridisation

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28
Q

How can chromosomes be examined?

A

light microscopy

29
Q

Why would we sequence DNA?

A

the location and type of mutation can be found

30
Q

What advancement has allowed the automation of sequencing?

A

the use of flourescently labelled ddNTP terminators (fluoroscopes can differ in colour for each base)

31
Q

When do mutations normally occur?

A

Cell divison

From intrinsic and extrinsic attacks on DNA

32
Q

What is the most common mutation?

A

C to T at CpG

C can methylate and deaminate to thymine

33
Q

What is the most common effect pf C->T mutations?

A

CGA->TGA

arginine->STOP

34
Q

Give 3 extracellular agents causing mutations

A

UV
chemicals
Ionizing radiation

35
Q

How would UV light cause DNA damage?

A

cross-linking of adjacent thymines to from a stable dimer, stalling DNA replication

36
Q

How would environmental chemicals damage DNA?

A

interpolate into DNA
cause DNA breaks
chromosome aneuploidy

37
Q

What would you call a mutation present in an egg or sperm?

What would it be othersie

A

Germline, they would otherwise be somatic

38
Q

What happens when the DNA mismatch repair gene is mutated?

A

leads to the accumulation of somatic mutations, leading to cancers

39
Q

Ideally, how would DNA double strand breaks be repaires?

A

The sequence from the other homologous chromosome of the pair would be used to synthesise the missing DNA

40
Q

What is a missense mutation?

A

A single nucleotide polymorphism which alters the amino acid being coded for

41
Q

What are nonsense mutations?

A

change from an amino acid codon to a stop codon, forminga truncated protein

42
Q

What effect might silent mutations have on splicing?

A

They may create a cryptic splice site, where a sit that isn’t normally spliced may interact with the spliceosome.

43
Q

What measures does the cell have to limit damage done via nonsense mutations?

A

nonsense mediated decay processes

44
Q

What are frameshift mutations?

A

insertion or deletion of base pairs producing a stop codon downstream

45
Q

what happens when short tandem repeats mispair?

A

they cause pathogenic deletions and insertions which cause a frameshift

46
Q

How would you prepare a karyotype from peripheral lymphocytes?

A

collect venous blood, remove RBC’s, add a culture medium to WBC’s and incubate for 3 days at 37 degrees.
Add colchine and remove the WBC;s, then add a hypotonic saline.
Fix the cells and spread over a slide, to be stained and photgraphed

47
Q

What are the different arms of chromosomes called?

A

p - short (petit)

q - long

48
Q

What are light bands in chromosomes?

A

less condensed chromatin, replicating early on in S phase (GC rich)

49
Q

What are the dark bands in chromosomes?

A

condensed chromatin, replicating late and AT rich

50
Q

What is the significance of DNA being linear?

A

Chromosomal anomalies can cause multi-organ problems

Alleles closer together are more likely to be inherited together

51
Q

What is Array CGH used for?

A

Array Comparative Genomic Hybridisation - DNA competes for the same probe sites on the microarray, allowing us to look at the whole genome body in greater detail than down the microscope in FISH.

52
Q

How does Array CGH work?

A

The patient and reference DNA compete for the same probe sites on the microarray.
If they are in equal amounts, they hybridise equally

53
Q

What are the types o numerical chromosomal anomalies?

A

Aneuploidy - monosomy and trisomy

Polyploidy - triploidy

54
Q

What is the relative severity of anomolies to sex chromosomes?

A

not too bad tbh

55
Q

What is a karyotype?

A

the international representation of genotypes

56
Q

What is the karyotype of Down Syndrome?

What are thought to be its’ main genetic bases?

A

47 XX+21
3 copies of 21 ‘Gene dosage effect’
‘amplified developmental instability’
Extra copy of chromosome 21 because of Robertsonian translocation
Mosaicism with normal and trisomy 21 cell lines

57
Q

What is the karyotype of Edwards syndrome?

A

47 XX +18

58
Q

What is the karyotype of Patau Syndrome?

What are the effects of this?

A

47 XX +13

Affects midline structures particularly incomplete lobation of the brain

59
Q

What are some sex chromosome anomalies?

A

Turner syndrome

Klinefelter syndrome

60
Q

What is the karyotype of Turner syndrome?

A

45 X

61
Q

What is the karyotype of Klinefelter syndrome?

A

47 XXY

results in poorly developed sexual characteristics, but has no effect on learning

62
Q

From where would errors leading to aneuploidy be inherited?

A

Most likely the maternal side

BUT NOT 46 XYY, which is lways inherited parentally

63
Q

Why do trisomies appear to be associated with an increase in maternal age?

A

lengthly interval between onset and completion of meiosis
Accumulating effects on the oocyte during this phase may damage the cell’s spindle
Wear and tear makes non-disjunction more likely

64
Q

Name 4 endogenous mechanisms causing DNA damage

A

depurination
Deamination
reactive oxygen
methylation of cytosines

65
Q

How does depurination work?

A

spontaneous fission of link between purine base and sugar, causing the loss of adenine or guanine from helix (deletion of base in new strand)

66
Q

How does deamination work?

A

cytosine deaminates to uracil, causing the substitution of A in the new strand

67
Q

How would oxygen damage DNA?

A

attacks rings

68
Q

what is the most common mutation mechanism?

A

deamination;

C to T at CpG dinucleotide

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