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Sem 1: Genetics > Week 2 > Flashcards

Week 2 Flashcards

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1
Q

What was the proportion of tall pea plants to small pea plants that Mendal found?

A

787:277
2.84:1
Tall peas : dwarf plants

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2
Q

What is the ratio found in a dihybrid cross?

A

9 : 3 : 3 : 1

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3
Q

What is the phenotypic ration of partial dominance?

A

1 : 2 : 1

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4
Q

Why aren’t lower cases used in incomplete dominance?

A

As there is no clear dominance relationship, so the 2 alleles are denote as R1 and R2

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5
Q

What are the genotypic relationship between F2 generation snapdragon (Antirrhinum) where P1 has a red flower and white flower?

A

1 - red flower
2 - pink flowers
1 - white flowers

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6
Q

What is codominance?

A

Two alleles of a gene produce a distinct, detectable gene product and detectable effects on phenotypes

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7
Q

What is the difference between incomplete dominance and codominance?

A

Incomplete dominance they is no clear two products of genes having an impact, where codominace there is a clear example of both genes working.

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8
Q

What is the human MN blood group?

A

A red blood cell glycoprotein antigen existing in two forms M and N

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9
Q

Where is the human MN gene found?

A

MN gene controlled by autosomal (chromosome 4) locus (L)

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10
Q

What are the 3 potential expressions of the MN gene?

A

2 x L^M = M
L^M x L^N = MN
2 x L^N = N

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11
Q

Whay s the ratio of the MN gene?

A

1/4 M and 1/4 N
1/2 MN

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12
Q

What are the 4 blood types and what are there antigens and antibodies?

A

Blood type : Antigen : Antibody
A : A : anti-B
B : B : anti-A
AB : A+B : neither
O : neither : anti-A and anti-B

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13
Q

What is the relationship between the 3 blood genes?

A

A and B are codominant but both are dominant to O

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14
Q

How are the 3 blood types written out as genes?

A

I^A
I^B
I^O

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15
Q

What is the presubstance to the antigens to blood types and what does it contain?

A

H substance
Fucose – Galactose – AcGluNH (N-acetyl galactosamine)

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16
Q

What allows for fucose to the H substance precursor?

A

FUT 1 allele

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17
Q

What does I^A do?

A

I^A directs the addition of N-acetylgalactosamine to H substance

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18
Q

What does I^B do?

A

I^B directs the addition of galactose to the H substance?

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19
Q

What does I^O do?

A

I^O does nothing do the final antigen is just the H substance

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20
Q

What happens if there is a mutation that abolish the function of a essential gene?

A

The mutations are lethal to embryos

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21
Q

What is the genotype of the survivors of recessive lethals mutations?

A

1:2
Homozygous Dominant : Hetrozygous

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22
Q

What is the genes involved in mouse coat colour?

A

AA - agouti
AA^Y - Yellow
A^YA^Y- Lethal

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23
Q

Which is dominant A or A^Y in mice?

A

A^Y is dominant in terms of cout colour but A is dominant in terms of survival

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24
Q

What are the end result of domiant lethal alleles?

A

They are usually lost from the population as they can’t be maintained in a heterozygous state except in cases of late onset

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25
Q

What are the genes of Huntington diseases?

A

HH - individuals exhibit early onset
Hh - individuals often exhibit late onset (40<) so chance gene can pass on to the mutant gene to children

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26
Q

What is epistasis?

A

One gene pair masks or modifies the expression of another gene

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27
Q

What were the type of genes that Mendel investigated?

A

Discontinuous (discrete i.e all or nothing)

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28
Q

What is gene interaction?

A

More than one protein maybe required for developement of a single phenotype

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29
Q

Who is the Bombay women?

A

She is a women from Bombay indicated she must carry I^B allele but phenotypically was blood group O

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30
Q

What was the mutation that the Bombay women had?

A

She had a mutation in the fut1 allele which prevented the formation of complete H substance therefore supressing A and B antigen production

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31
Q

What is the relationship between fut1 gene to I^A and I^B

A

The fut1 gene is epistatic to the I^A and I^B gene

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32
Q

What happens to the Bombay women with the H substance?

A

As the group isnt produced so she produces anti-H antigen antibodies. This makes her at risk for getting haemolytic transfusion if they blood group O blood.

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33
Q

What does the ‘I’ mean in blood types?

A

Isoglutinogen

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34
Q

What is duplicate recessive epistasis?

A

When the recessiveness of two genes can impact the expression of phenotype

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35
Q

How does duplicate ressive epistasis impact the flower colour of Sweat Peas?

A

Hetrozygous or Homozygous domiant for both genes are required for the leaves to be purple

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36
Q

What happens in sweat peas if the ‘a’ gene is homozygous recessive?

A

The precursor substance is unable to be converted to the intermediate substance

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37
Q

What happens in sweat peas if the ‘b’ gene is homozygous recessive?

A

The precursor substances can be converted into the intermediate substance but can’t them be converted into the final product so the flower stays white

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38
Q

What is the ratio of purple sweat pea flowers to white flowers?

A

9 purple to 7 white
7 white can be broken down into 3 A_bb : 3 aaB_ : aabb

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39
Q

What is the phenotype ratio of F2 Drosophila melanogaster eye colour where the first generation is brown x scarlet and F2 is wildtype?

A

9 wild type (brick red colour)
3 brown
3 scarlet
1 white

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40
Q

What genes are working in order for the wild type eye colour in Drosophilia melanogaster?

A

Both the brown and scarlet genes are working allowing for the production of drosopterin and xanthommatin

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41
Q

What is needed for the eye colour of Drosophilia melanogaster to be scarlet?

A

The flies have the 2 recessive scarlet genes meaning they do not make xanthommatin so dont produce any brown pigment

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42
Q

What is needed for the eye colour of Drosophilia melanogaster to be brown?

A

The flies have to have 2 recessive brown genes meaning drosopterin so do not produce any scarlet pigment

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43
Q

What is needed for the eye colour of Drosophilia melanogaster to be white?

A

The fly needs to be homozygous resessive in both brown and scarlet meaning neither xanthommatin or drosopterin are produced

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44
Q

What are the phenotypes of F1 Dosophilia when the mother has wildtype eyes and father has white eyes?

A

All the males and females have wildtype eyes

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45
Q

When the F1 Dosophilia, mother WT and father White, reproduce what is the phenotype of their childrens eyes?

A

All the female eyes are wildtype
Half of the male eyes are wildtype
Half of male eyes are white

46
Q

What are the phenotypes of F1 Dosophilia when the mother has white eyes and father has wildtype eyes?

A

All the female eyes are wild type
All the male eyes are white

47
Q

When the F1 Dosophilia, mother white and father wildtype, reproduce what is the phenotype of their childrens eyes?

A

Half females have red eyes
Half females have white eyes
Half male have red eyes
Half males have white eyes

48
Q

What is the term used used to describe males in x linkage?

A

‘hemizygous’ as they only have 1 x chromosome so cant be homozygous and heterozygous

49
Q

What is gene drive?

A

The function is to cause non-Mendelian inheritance patterns and the rapid spread of transgenes through a population

50
Q

What is the purpose of gene drive?

A

Designed with payloads (genes) that cause desired traits

51
Q

What is the current method for gene drive?

A

CRISPR-Cas9

52
Q

What does CRISPR stand for?

A

Clustered Regularly Interspaced Short Palindromic Repeats

53
Q

What does Cas9 stand for?

A

CRISPR associated protein 9

54
Q

What does gRNA mean?

A

Guide RNA

55
Q

What is the first stage of gene drive?

A

Guide RNA guides Cas9 to the section of DNA which allows Cas9 to cut the DNA. Then the Cas9 and gRNA are inserted into the DNA with any DNA inbetween

56
Q

What is the second stage of gene drive?

A

Homologous Directed Repair fixes the DNA strand building the DNA of the Cas9 and gRNA to complete the other strand

57
Q

Does gene grive only impact 1 allele?

A

No the second allele is also rebuilt as the first allele will code for cas9, gRNA and any DNA inbetween which then inserts itself into the other allele

58
Q

Will gene drive impact future generations?

A

Theoretically yes as the children will inherit 1 mutated allele which will then insert itself into the other gene. This will repeat across all future generations

59
Q

What are 3 examples of genes that can be inserted to reduce mosquito (Anopheles stephensi) related infection?

A

Altered Akt - increase signalling response to human blood insulin and reduced Plasmidium falciparum infection by 66-99%

Anti-P. falciparum circumsporozoite protein (PfCSP) single-chain antibody (scFv) reduce parasite transmission of parasite to mice from 83% to 25%

Two single-chain antibodies (scFv) that target pathogen circumsprozoite protein and chitinase. Using gene drive this was introgressed into ~99.5% of the progeny

60
Q

How can genes be resistant to CRISPR induced cleavage?

A

The cleavage is repaired by non-homologous end-joining (NHEJ). This means that mutated sites are no longer recognised by the drives gRNA

61
Q

How have scientists overcome the resistance challenges by non-homologous repair?

A

They target the Anopheles gambia doublesex (dsx) gene

62
Q

What happens when the doublesex gene is targetted?

A

Males are normal but females are sterile
No resistance observed
In caged population, proportion of modified individuals increased and modified egg production reduced progressively from one generation to the next
Total population collapse

63
Q

What is molecular genetics?

A

The study of how differences in the structure (or expression) of DNA manifests as phenotype variations in organisms

64
Q

What are the core field mergings in molecular genetics?

A

Medelian inheritance, molecular biology and biotechnology

65
Q

What is the aim of molecular genetics?

A

Link gene sequences to phenotypes/ link mutations to genetic conditions

66
Q

What is the central dogma of molecular biology?

A

The process by which instructions in DNA are converted into a functional product.

67
Q

Who and when was this central dogma first proposed?

A

Francis Crick in 1958

68
Q

What does the central dogma suggest?

A

That DNA contains the informations needed to make all of our proteins, and that RNA is a messenger that carries this information to the ribosome

69
Q

What happens with a mutation in the enhancer?

A

Reduction or increase in amount of gene product

70
Q

What happens with a mutation in the promoter?

A

Reduction or increase in amount of gene product

71
Q

What happens with a mutation in the start codon?

A

Abolition of translation or aberrant translation

72
Q

What happens with a mutation in the exon donor consensus or the exon acceptor consensus?

A

Aberrant splicing - non functional protein

73
Q

What happens with a mutation in the stop codon?

A

Failure of translation termination - carboxy terminal extension of protein

74
Q

What happens with a mutation in the Poly(A) addition signal?

A

Failure of polyadenylation - reduced mRNA stability and reduced protein

75
Q

Why molecular genetics important?

A

Studies structure and function of gene at molecular level - allows us to combine patterns of inheritance with studies of gene structure to understand molecular function

76
Q

What is the advantage of molecular genetics over classical genetics?

A

Classical genetics requires a phenotype. Not all allelic variation produces a phentotype and phentypes can be affected by envrionement.
Molecular genetics can identify and track subtle sequence differences

77
Q

What is the phenotypic ratio for two heterozygous parents?

A

3:1 (Dominant trait: Recessive trait)

78
Q

What is the genotypic ratio for two heterozygous parents?

A

1:2:1 (Homozygous dominant: Heterozygous: Homozygous recessive)

79
Q

What allows for Restriction Fragment length Polymorphism?

A

Sequence variation creates unique sites for restriction endonucleases e.g. EcoRI

80
Q

When was Restriction Fragment length Polymorphism invented?

A

1984

81
Q

What 2 processes after introduction of restriction enzymes are used?

A

Gel electrophoresis and southern blot

82
Q

What were the early uses of Restriction Fragment length Polymorphism?

A

Genome mapping
Indentifying genetic disorders
Paternity testing

83
Q

What are the problems of Restriction Fragment length Polymorphism?

A

Large amounts of DNA
Probe label design
Length Southern Blot procedure

84
Q

Is Restriction Fragment length Polymorphism used today?

A

Largely obsolete due to increasily inexpensive DNA sequencing

85
Q

What is PCR?

A

Polymerase Chain reaction allowing for the genotyping of individuals and loci

86
Q

How does PCR work?

A

Extract whole DNA
Produce an ‘amplicon’ region of targeted amplification using primers

87
Q

What are the 3 stages of PCR and their temperatures?

A

Denaturing stage= 94-95 degrees C
Annealing stage= 50-56 degrees C
Extending stage= 72 degrees C

88
Q

Why is restriction digest of PCR amplicons more effective than Restriction Fragment length Polymorphism?

A

Much faster due to PCR creating many copies of the gene that needs to be targeted

89
Q

What is the downside of restriction digest of PCR?

A

Still need a mutation to have introduced a recognition site

90
Q

How can PCR products be determined without restriction enzymes?

A

The change in size of PCR products on a gel electrophoresis

91
Q

What is the first step of sanger sequencing?

A

PCR with fluorescent chain-terminating ddNTPs

92
Q

What is the second step of sanger sequencing?

A

Size seperation by capillary gel electrophoresis

93
Q

What is third step of sanger sequencing?

A

Laser excitation and detection by sequencing machine

94
Q

In a output chromatogram in sanger sequencing what does a larger peak mean?

A

The confidence in result

95
Q

How is Sanger sequencing important for PCR?

A

Sanger sequencing is a downstream method for PCR results

96
Q

What is the steps in whole genome sequencing for the reference gene ie Human Genome Project?

A

Break genome into larger fragments
Order clones
Break individual clones into small pieces
Generate thousands of sequence reads and assemble sequence of clone
Assemble sequence reads of overlapping clones to establish reference sequence

97
Q

What are the steps for generating a persons genome sequence?

A

Break genome into small pieces
Generate millions of sequence reads
Align sequence reads to established reference sequence
Deduce starting sequence and identify differences from reference sequence

98
Q

What is the size and frequency (1 per x kb) of SNP mutation?

A

1bp
1 per 1kb

99
Q

What is the size and frequency (1 per x kb) of InDel?

A

1-100bp
1 per 10kp

100
Q

What is the size and frequency (1 per x kb) of SSR?

A

1-10bp
1 per 30kp

101
Q

What is the size and frequency (1 per x kb) of CNV?

A

10bp-1Mb
1 per 60 kb

102
Q

What is the size and frequency (1 per x kb) of Inversions?

A

1bp> 1Mb
1 per ?

103
Q

What is SNP?

A

Single Nucleotide Polymorphism

104
Q

What can SNP affect?

A

mRNA stability
Promoter activity
Peptide formation

105
Q

What are InDel?

A

Insertion or deletion of a single stretch of DNA sequence (2nd most common)

106
Q

What commonaly causes InDel mutations?

A

DNA replication or DNA repair (NHEJ)

107
Q

What is SSR?

A

Simple Sequence Repeat
Sequence of one to a few bases that repeat in tandem form <10 times to >100 times

108
Q

What are SSR with larger repeating units?

A

Are less frequent and will be classified as Copy Number Variants (CNVs)

109
Q

What is the cause of Huntintons disease?

A

The more SSR regions the more severe the symptoms ie 20-30 no conditions, 50-99 late onset and 100 or more early-onset disease, the more repeats the earlier the symptoms

110
Q

How can genotyping help with determining if a person has sickle cell disease?

A

As it is caused by a single nucleotide changing from an A to a T (it is homozygous recessive)

111
Q

How can gene editing help cure Sickle cell disease?

A

Use lentivirus to code for normal beta-globin gene
Use CRISPR to inactivate the inhibitor for y-globlin- alternative to beta-globin but only during fetal development
Use CRISPR to swap the mutated beta-globin gene for the normal sequence fully repairing the sickle cell mutation

Sem 1: Genetics (10 decks)

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