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Chromosomes and genes > Lecture 9 and 10 > Flashcards

Lecture 9 and 10 Flashcards

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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?

Study These Flashcards
A

Crossing over becomes physically impossible with decreased distance between loci

25
What is the maxium distance on genetic maps and why?
50 RF (cM) because double cross over occurs
26
What name is given to places where the recombination rate is higher then expected?
Recombinant hotspots
27
Recombination and interference are _____ events.
Controlled
28
How does recombination differ in human males and females?
Recombination rate twice in males then females
29
What are the two types of point mutation?
``` Forward mutation (away from ancestral sequence) Reverse mutation (back to ancestral sequence) ```
30
Who first showed that x-rays generate mutation of drosophilia?
Thomas Hunt Morgan
31
What diseases often have a neurological phenotype?
Trinucleotide repeat diseases
32
What do trinucleotide repeat diseases show?
Anticipation (disease onset gets younger down the generation)
33
What enzyme works during photo repair and what does it do?
Photolyase recognises thymine dimers and reverses
34
Why is this mechanism called photo repair?
Only works in the presence of light
35
How is guanine removed?
Alkyltransferase
36
What proteins scan DNA for distortion in nucleotide excision repair?
UvrA and UvrB
37
What happens when distortion is found in nucleotide excision repair?
UvrC combines with UvrB and nick the DNA at 7 and 4bp
38
What happens after the DNA has been nicked during nucleotide excision repair?
DNA polymerase fills the gap, ligase joins new to old
39
What enzyme recognises and removes bases during base excision?
Glycosylase
40
What site is left behind after glycosylase removes a base?
Apurinic or apyrimidinic site
41
What enzyme recognises and makes a single strand break during base excision?
AP endonuclease
42
What happens after AP endonuclease is done?
Exonuclease removes a few bases which is then backfilled with polymerase and ligase
43
What type of repair occurs when double strand breaks happen?
Nonhomologous end joining
44
What type of repair correct polymerase errors by copying existing strand?
Methyl-directed repair
45
How does methyl-directed repair detect original strand?
``` Methyl group (only in bacteria) Errors identified and replaced using base excision repair ```
46
What is an auxotroph?
A strain that needs a specific supplement
47
What is a prototroph?
An organism that can grown on minimal media
48
What bread mould was experimented on?
Neurospora crassa
49
What did Beadle and tatum propose by testing each supplement?
One gene=one enzyme
50
What is black urine disease known as?
Alkaptonuria
51
Who studied Alkaptonuria in families?
Archibald Garrod
52
What did Garrod find?
Homogentisic acid accumulates in the urine, enzyme that breaks this down is absent in the patients
53
What enzyme is mutated in phenylketonuria?
Phenylalanline hydroxylase
54
Retina cells have ______ transmembrane proteins.
7
55
Each retina cell evolved from the orginal ____ gene.
Rhodopsin
56
How many light sensitive proteins are there in rod and cone cells?
4
57
How many single variants in the rhodopsin gene lead to progressive sight loss? reduce sensisitivty to light?
29 | 2
58
What variant in the red receptor causes red colour blindness?
Cys203>Arg variant

Chromosomes and genes (10 decks)

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