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Chromosomes and genes > Lecture 9 and 10 > Flashcards

Lecture 9 and 10 Flashcards

1
Q

What is linkage and mapping?

A

The process of finding out how genes are structured in the genome

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2
Q

Who conducted a dihybrid cross and got some rando results?

A

Sunders and Bateson

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3
Q

What were the expected dihybrid cross results vs observed?

A

9:3:3:1
11:1:1:3
(Over representation of parental phenotypes)

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4
Q

What were Sunders and Bateson crossing?

A

Sweet pea flower colour and pollen shape

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5
Q

What species did Thomas Hunt Morgan work with?

A

Drosophilia Melanogaster

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6
Q

What did Morgan investigate?

A

Traits that followed a sex linked pattern of inheritance (body colour, eye colour, wing length)

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7
Q

What did the F1 generation of Drosophilia Melanogaster contain?

A

Wild type females

Yellow bodied, white eyed, minature winged males

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8
Q

What was Morgan’s explanation for a higher proportion of the F2 generation having parental combinations?

A

All three genes located together, transmitted together

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9
Q

What is recombination frequency?

A

Proportion of offspring not of either parents phenotype

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10
Q

How can we tell Morgan’s results weren’t a fluke?

A

Chi squared test

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11
Q

What is the chi squared test formula?

A

x^2=TOTAL (number observed-number expected)^2/number expected

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12
Q

When is a p value significant?

A

less than 0.001?

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13
Q

Who and when were the first genetic map constructed?

A

Alfred Sturtevant, 1911

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14
Q

1% recombination frequency=

A

1cM = 1 map unit

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15
Q

How to find RF using crossing?

A

Add up all individuals recombinant for two pairs of gene and divide by total individuals

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16
Q

Who visualised recombination using microscope?

A 
McClintock and Creighton (Maize)
Curt Stern (Drosophilia)
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17
Q

Why is maize a good model?

A

Each cob has hundreds of kernel, an outcome from a cross

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18
Q

Maize had what abnormal chromosome, visible under a microscope and use as a genetic marker?

A

Chromosome 9

No known phenotypic effect

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19
Q

What are the kernel colour genotypes for maize?

A

C coloured

c colourless

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20
Q

What are the kernal endosperm texture genotypes for maize?

A

Wx starchy endosperm

wx waxy endosperm

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21
Q

What were McClintock and creighton’s conclusions?

A

Cross over occured between C and wx gene, genetic recombination involves physical exhcnage of segments

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22
Q

What do double recombinants do?

A

Shrink map distance if not counted

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23
Q

Why are the number of double recombinants lower then expected?

A

Interference

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24
Q

What is interference?

A

Crossing over becomes physically impossible with decreased distance between loci

25
Q

What is the maxium distance on genetic maps and why?

A

50 RF (cM) because double cross over occurs

26
Q

What name is given to places where the recombination rate is higher then expected?

A

Recombinant hotspots

27
Q

Recombination and interference are _____ events.

A

Controlled

28
Q

How does recombination differ in human males and females?

A

Recombination rate twice in males then females

29
Q

What are the two types of point mutation?

A 
Forward mutation (away from ancestral sequence)
Reverse mutation (back to ancestral sequence)
30
Q

Who first showed that x-rays generate mutation of drosophilia?

A

Thomas Hunt Morgan

31
Q

What diseases often have a neurological phenotype?

A

Trinucleotide repeat diseases

32
Q

What do trinucleotide repeat diseases show?

A

Anticipation (disease onset gets younger down the generation)

33
Q

What enzyme works during photo repair and what does it do?

A

Photolyase recognises thymine dimers and reverses

34
Q

Why is this mechanism called photo repair?

A

Only works in the presence of light

35
Q

How is guanine removed?

A

Alkyltransferase

36
Q

What proteins scan DNA for distortion in nucleotide excision repair?

A

UvrA and UvrB

37
Q

What happens when distortion is found in nucleotide excision repair?

A

UvrC combines with UvrB and nick the DNA at 7 and 4bp

38
Q

What happens after the DNA has been nicked during nucleotide excision repair?

A

DNA polymerase fills the gap, ligase joins new to old

39
Q

What enzyme recognises and removes bases during base excision?

A

Glycosylase

40
Q

What site is left behind after glycosylase removes a base?

A

Apurinic or apyrimidinic site

41
Q

What enzyme recognises and makes a single strand break during base excision?

A

AP endonuclease

42
Q

What happens after AP endonuclease is done?

A

Exonuclease removes a few bases which is then backfilled with polymerase and ligase

43
Q

What type of repair occurs when double strand breaks happen?

A

Nonhomologous end joining

44
Q

What type of repair correct polymerase errors by copying existing strand?

A

Methyl-directed repair

45
Q

How does methyl-directed repair detect original strand?

A 
Methyl group (only in bacteria)
Errors identified and replaced using base excision repair
46
Q

What is an auxotroph?

A

A strain that needs a specific supplement

47
Q

What is a prototroph?

A

An organism that can grown on minimal media

48
Q

What bread mould was experimented on?

A

Neurospora crassa

49
Q

What did Beadle and tatum propose by testing each supplement?

A

One gene=one enzyme

50
Q

What is black urine disease known as?

A

Alkaptonuria

51
Q

Who studied Alkaptonuria in families?

A

Archibald Garrod

52
Q

What did Garrod find?

A

Homogentisic acid accumulates in the urine, enzyme that breaks this down is absent in the patients

53
Q

What enzyme is mutated in phenylketonuria?

A

Phenylalanline hydroxylase

54
Q

Retina cells have ______ transmembrane proteins.

A

7

55
Q

Each retina cell evolved from the orginal ____ gene.

A

Rhodopsin

56
Q

How many light sensitive proteins are there in rod and cone cells?

A

4

57
Q

How many single variants in the rhodopsin gene lead to progressive sight loss? reduce sensisitivty to light?

A

29

2

58
Q

What variant in the red receptor causes red colour blindness?

A

Cys203>Arg variant

Chromosomes and genes (10 decks)

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