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Quiz Flashcards

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Biology 101 flashcards
1
Q

When does crossing over happen?

A

Meiosis 1- in prophase 1

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2
Q

Describe what happens in mitosis

A

IN prophase chromosomes duplicate
In metaphase align in single row down centre
In anaphase sister chromatids separate–>daughter cells x 2 with full single copy of genetic material

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3
Q

Describe what happens in meiosis

A

In meiosis I, there is crossing over during prophase 1
IN metaphase 1, the chromosomes align in PAIRS down the centre of the cell like noahs ark
In anaphase the pairs are separated but sister chromatids stay together. Haploid cells created
In meisosis 2 the sister chromatids separate so that each of the FOUR cells has half a full set of chromosomes.

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4
Q

What is the role of rRNA and tRNA?

A

involved in protein synthesis (translation)

directly for ribosomal RNAs or transfer RNAs

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5
Q

What are introns and exons?

A

Introns between exons

Exons code for protein

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6
Q

Why might someone be “mutation negative” even though have the disease?

A

Mutation in promotor region.

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7
Q

Features of Kleinfelters

A

MOST COMMON CAUSE OF PRIMARY MALE HYPOGONADISM
Low testosterone
Infertility, incomplete virilisation, gynaecomastia
Tall
Mild learning difficulties, immature, shy

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8
Q

Turners describe

A 
Short
Widely spaced nipples
NORMAL intellect
BICUSPID aortic valve and COARCTATION
Web neck 
Infertility, ovarian dysgenesis
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9
Q

Why is it called a microdeletion syndrome?

A

Have to delete 3-5 million base pairs before see on karyotype.

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10
Q

Is it worse to inherit myotonic dystrophy from mum or dad?

A

Mum
Trinucleotide repeat
Mum Did it

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11
Q

Is it worse to inherit HD from mum or dad?

A

Dad

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12
Q

What are the three major players in gene regulation?

A

Methylation
Histone modification
Non coding RNA

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13
Q

If you methylate a promoter region, what happens?

A

Gene silenced

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14
Q

What is the mechanism of imprinting?

A

Methylation of CpG rich domains and modification of histone proteins

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15
Q

True or false, imprinting is reset during gamete formation?

A

True

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16
Q

Defect in prader-Willi

A

Loss of paternally active 15q gene copy -either both 15qs are maternal (maternal UPD), or deletion on paternal 15 (most), and a minority from IMPRINTING

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17
Q

How do you get Angelman syndrome?

A

Deltion of maternal 15q12 (most)
Paternal UPD
UBE3A mutation
Imprinting defects

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18
Q

How/what mechanism with gametes produces UPD?

A

“rescue” mechanism when zygote is formed with accidentally having three chromosomes after NON-DISJUNCTION- and one is thrown out.

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19
Q

Best way to detect mosaicism

A

Microarray or next gen sequencing

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20
Q

What is the significance of SNPs?

A

1 in 300 bases is polymorphic
Usually in non coding regions
Can indicate susceptibility to disease, response to drugs, susceptibility to infection

Warfarin metabolism is often dictated by SNP pattern

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21
Q

Cytogenetics is to what as molecular cytogenetics is to what?

A

Karyotype
FISH or molecular karyotype

Fish is still used for looking at balanced rearrangement but otherwise replaced by chromosomal microarray

22
Q

What do red and green mean on a chromosomal microarray?

A

Green means loss material

Red means gain of material

23
Q

What does SNP microarray not detect?

A 
Balanced rearrangements
Whole or partial gene deletions
Triplet expansion 
Sequence changes
Methylation changes
24
Q

What does next gen sequencing do?

A

Sequences the whole genome
More economical than individual gene sanger sequencing
CANNOT DETECT trinucleotide repeat or methylation defects

25
Q

What type of problem is most likely to cause a disease that could be found by classic linkage analysis?

A

Protein truncating variant.

26
Q

Describe the problem in BCR-ABL?

A

BCR originally on 22, ABL originally on 9. Translocation so that BCR next to ABL on chromosome 22.

27
Q

How do you work out carrier frequency?

A

square root of (disease frequency/4)

28
Q

How do you work out disease frequency?

A

Carrier squared then times by 4

29
Q

What does the Hardy Weinberg Equation say?

A

p^2 + 2pq + q^2 = 1 where p is the frequency of one allele and q is the frequency of the other. When multiply it out-
pxp is the number of people homozygous for p, 2pq is the proportion of people heterozygous, and q x q is the number of people homo for q.

30
Q

What percentage of genes are shared with first degree, second degree and third degree relative?

A

50%
25%
12.5%

31
Q

What is Lyonisation?

A

Another term for X inactivation where in females only one chromosome is doing anything from early on in development. Happens randomly so all females are mosaic. If skewed, female carrier can manifest the condition of their X non inactivated. ie protect from X linked dominant or cause X linked recessive expression

32
Q

Two examples of X linked dominant?

A

Rett syndrome

X linked hypophosphataemic rickets

33
Q

Pedigree pattern: imprinting

A

Seems to skip some generations
All affected kids are from either only a man or only a woman
Otherwise autosomal so 50% chance of passing on

34
Q

If it’s a paternally imprinted mutated gene, what do you expect?

A

none of the children of the male will be affected

half of the children of the female will be affected

35
Q

Can you use maternal mutant load when assessing mitochondrial disorder to predict risk for fetus?

A

No. Not all mitochondria are replicated to daughter cells during oogenesis. No way to predict.

36
Q

Some cells have the mutated mitochondria, others do not. Called-

A

Heteroplasmy.

37
Q

Pedigree with mitcohondrial inheritance

A

All maternally inherited

Males and females affected just as commonly

38
Q

What is linkage disequilibrium?

A

Where there is a tendency for genes to be inherited together in a non random fashion because close together in chromosomal position- unlikely to be separated by crossing over at meiosis. Note HLA types not causing disease but just going along for the ride

39
Q

What does the 2/3 rule say?

A

If unaffected sibling of someone with an AD disorder, 2/3 chance that you are a CARRIER, 1/3 chance that you are non disease non carrier.

Note does not apply if sibling not affected.

40
Q

How many CAG repeats in HTT gene before fully penetrant?

A

40

But Cannot use the number of repeats to predict phenotype with accuracy

41
Q

Most common heart defect in Downs syndrome

A

VSD

then endocardial cushion defect>PDA>ASD>TOF

42
Q

Marfan clinical features

A 
Tall stature
Joint hypermobility
Aortic dissection, AR/MR
Pectus carinatum over excavatum
Lens dislocation up 
Flat foot
43
Q

Mutation in marfan?

A

FBN1 mutation

AD

44
Q

Some disease associations with Down’s

A 
Hypothyroid
Coeliac
Leukaemia
AA instability 
Dementia
45
Q

How many copies of CGG repeat until fragile X expression?

A

200 copies

46
Q

What is the best way to tell the difference between mitochondrial transmission and X linked?

A

Same severity of disease in males and females affected in mitochondrial.

47
Q

Advanced maternal age increases the risk of what?

A

Non disjunction

48
Q

Advanced paternal age increases the risk of

A

some AD diseases like achondroplasia

49
Q

What does helicase do?

A

Unwinds the dsDNA

50
Q

What is the direction of replication of DNA polymerase?

A

Has to add 5 prime to 3 prime. This means the lead stand starts with 3 prime as the template.
Needs an RNA primer to start it off.

51
Q

How do transcription factors work?

A

Regulate binding of RNA polymerase

52
Q

How do small interfering RNAs work to regulate gene expression?

A

Enhance breakdown of mRNA

GENETICS (5 decks)

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