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BIOC192 2024 > Lecture 17 - Genetic Variation & Disease #1 > Flashcards

Lecture 17 - Genetic Variation & Disease #1 Flashcards

1
Q

How much DNA do diploid organisms receive from each parent?

A

1/2

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2
Q

What is DNA packaged onto?

A

CHromosomes

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3
Q

What does each chromosome have?

A

a particular set of genes in a particular order

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4
Q

How many of each chromosome does a diploid organism have?

A

two of each chromosome (one from each parent)

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5
Q

Will the chromosomes from each parent be identical?

A

NO

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6
Q

What is an allele?

A

an alternative form of a genetic variant

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7
Q

What is the criteria for an allele?

A

The variation must be located on the same place in the gene

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8
Q

What could happen with differing alleles?

A

You could have two different versions of a protein

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9
Q

When can we track an inheritance pattern?

A

when a genetic variant causes a visible/measurable change in phenotype

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10
Q

What is the phenotype?

A

the observable characteristics or traits in an individual

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11
Q

What determines phenotype?

A

genotype - combination of alleles a person has for a a particular genetic variant

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12
Q

What is a dominant allele?

A

an organism with at least one dominant allele will show that alleles phenotype

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13
Q

What is a recessive allele?

A

An organism will only show a recessive allele when both alleles are the same

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14
Q

What does the mode of inheritance an allele has depend on?

A

What the allele does to the protein and how the protein functions

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15
Q

Are the modes of inheritance for gain of function and loss of function alleles usually the same?

A

No usually different

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16
Q

What does a gain of function allele do?

A

causes the protein to work too well or do something new

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17
Q

What does a loss of function allele do?

A

causes the protein to no longer work

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18
Q

What type of inheritance pattern will gain of function alleles often show?

A

Often dominant because it is hard to hide the gain in function

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19
Q

What type of inheritance pattern do loss of function alleles often show?

A

recessive - because usually the other allele can compensate for the lost function

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20
Q

What is a monogenic trait?

A

An inherited trait/characteristic that is controlled by a single gene

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21
Q

What type of inheritance pattern will monogenic traits often follow?

A

Simple dominant/recessive inheritance patterns

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22
Q

Does the environment influence monogenic traits?

A

Yes sometimes ie. no. of freckles you have

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23
Q

What is a polygenic trait?

A

An inherited trait/characteristic that is controlled by multiple genes

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24
Q

Do polygenic traits follow a common inheritance pattern?

A

No, although they may may be common in a family, but can’t be characterised into dominant/recessive

25
Q

Are polygenic traits influenced by environment?

A

Yes usually

26
Q

What causes Retinitis Pigmentosa?

A

Variants in the Rhodopsin receptor protein

27
Q

What are symptoms of Retinitis Pigmentosa?

A

night-blindness, loss of complete vision over time

28
Q

What type of inheritance pattern does Retinitis Pigmentosa follow?

A

Dominant inheritance pattern

29
Q

Is Retinitis Pigmentosa monogenic or polygenic?

A

Monogenic

30
Q

What does the Rhodopsin receptor do?

A

Located in the rod cells in eyes and detects presence of light and sends signals to the brain

31
Q

What does the Rhodopsin receptor have to completely inactivate when there is no light present?

A

an ionic lock that helps make the receptor extremely responsive to light

32
Q

How does Retinitis Pigmentosa lead to loss of vision?

A

The genetic variants interuopt the ionic lock and make the rhodopsin receptors constantly active. This leads to the death of rod cells and loss of sight over time

33
Q

What is Phenylketonuria (PKU)?

A

The inherited inability to metabolise phenylalanine

34
Q

What are symptoms of PKU?

A

If untreated causes brain and nerve damage

35
Q

What inheritance pattern does PKU follow?

A

A recessive inheritance pattern, both gene must produce a non-functional enzyme in order to inherit the disease

36
Q

What does Phenylalanine hydroxylase do?

A

converts phenylalanine to tyrosine

37
Q

What happens when the phenylalanine hydroxylase enzyme doesn’t work well?

A

Leads to accumulation of phenylalanine and decrease in tyrosine, the increased phenylalanine in brain leads to brain damage

38
Q

What are some potential reasons why an increase in phenylalanine may cause brain damage?

A

MAY
- increase oxidative stress
- decrease cerebral protein synthesis
- alter neurotransmitter metabolism

39
Q

What can help treat PKU?

A

Low phenylalanine diet ensures minimal build up occurs

40
Q

What is genotyping?

A

the process of determining the specific genetic alleles in an organism’s DNA

41
Q

What are some ways to determine genotype?

A

PCR-RFLP, fluorescence-based methods (including gene chips), genome sequencing.

42
Q

What is the point of genotyping?

A

Often want to confirm presence/absence of a disease-causing allele. as this
* Could help point to specific cause of disease
* Confirm disease inheritance pattern
* Could predict future health/disease progression,

43
Q

What are the components of PCR?

A
  • DNA sample
  • Primers (small segment of DNA complementary to DNA sample)
  • Polymerase (heat tolerant enzyme)
  • Nucleotides (DNA nucleotides to build new strand)
44
Q

What is PCR?

A

Lab-based method to make many copies of specific segment of DNA using changes of temperature

45
Q

What happens during the 1st step of PCR?

A

Denaturation - DNA is seperated by heating to a very high temperature

46
Q

What happens to the DNA in each cycle of PCR?

A

Amount doubles

46
Q

What happens during the 2nd step of PCR?

A

Annealing - Reaction is cooled so DNA primers can attach to target sequence

46
Q

What happens during the 3rd step of PCR?

A

Elongation - Heat increased slightly so that heat tolerant DNA polymerase can bind primer and replicate DNA

47
Q

What does PCR-RFLP stand for?

A

Polymerase chain reaction-restriction fragment length polymorphism

48
Q

What is PCR-RFLP?

A

Genotyping method that uses PCR, restriction enzymes, and gel electrophoresis to determine genotype

49
Q

What are benefits of using PCR-RFLP?

A
  • Quick, simple genotyping method.
  • Easy to run in any DNA lab.
  • Scalable – can run just a few samples at once up to ~400 per gel.
50
Q

What is a restriction enzyme?

A

proteins isolated from bacteria that cut DNA (a bacterial defence mechanism)

51
Q

How does a restriction enzyme work?

A

Each restriction enzyme recognises a particular sequence and cuts that
sequence at a particular base on both strands. (sequence must be short and read the same forward and backwards)

52
Q

What is the process of PCR-RFLP?

A
  1. PCR primers amplify DNA around genetic variant of interest.
  2. Restriction enzyme cuts one allele of the variant but not the other
  3. DNA fragments are separated by size on a DNA gel. (smaller frags travel further, cut dna has 2 frags uncut only 1)
53
Q

How do fluorescence-based genotyping methods work?

A

Use different coloured probes to detect alleles

54
Q

What is the process of fluorescence based genotyping methods?

A
  1. PCR primers amplify DNA around variant of interest
  2. Probes specifically anneal to one of the two alleles
  3. As polymerase amplifies the DNA the probe is broken down and releases dye
  4. The specialised PCR machine detects the colour of the dye upon release
55
Q

What is a LightCycler?

A

A specialised PCR machine

56
Q

How are can you calculate which alleles are present via Fluorescence methods?

A

Clustering graphs (require enough samples to form a cluster need numerous samples)

57
Q

How can you detect 50000 - 100000 variants at once?

A

Genotyping chips - which use fluorescence based methods

BIOC192 2024 (25 decks)

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