Intro to Genetics Flashcards

1
Q

Examples of unifactorial diseases

A

Duchenne muscular dystrophy
Haemophillia
Phenylketonuria

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2
Q

Polygenic inheritance

A

Phenotype is determined by variants of many genes at diff loci, each allele exerting a small additive effect

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3
Q

Traits showing continuous distribution

A

Determined by interplay of many alleles at diff loci but influenced by environmental factors

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4
Q

Multifactorial

A

Phenotype results from the interaction of environmental (incl in utero environment) and genetic factors

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5
Q

Heritability

A

The proportion of variance in a characteristic attributed to genetic factors for a given pop.

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6
Q

Concordant

A

If both twins have same trait (incl complex disease phenotypes)

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7
Q

Discordant

A

If only one twin has the disease

Freq. of concordance is compared for mz and dz twins

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8
Q

Concordance rates in multifactorial traits

A

Degree of concordance in mz twins exceeds that seen in dz twins but is <100% as a result of diff environmental contributions

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9
Q

When are concordance rates the same in mz and dz twins

A

When the disease is caused directly by environmental factors

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10
Q

What do family and twin studies measure

A

Heritability

Heritability estimates can vary over times and between populations

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11
Q

What does the liability threshold model explain

A

Why we see family clustering for polygenetic and multifactorial traits e.g. heart disease and psychiatric disorders

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12
Q

Examples of autosomal dominant and autosomal recessive monogenic

A

Huntingtion disease

Hereditary haemochromatosis

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13
Q

Huntington disease

A

Classic single gene disorder
Inherited as autosomal dominant trait and underlying mutation has v. high penetrance - the chance that a carrier of the mutation (genotype) will eventually express the disease phenotype too

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14
Q

Mutation leading to Huntington’s

A

Expansion to CAG codon –> expressed as glutamine in the proteins AA sequence
Altered protein is toxic and causes progressive degeneration of the basal ganglia

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15
Q

Altered protein in Huntington’s

A

Altered protein is toxic and causes progressive degeneration of the basal ganglia and cerebral cortex’s resulting in a range of neurological symptoms
Toxic-gain of function phenotype —> degeneration

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16
Q

Transmission of Huntington’s

A

Pedigree shows vertical transmission

17
Q

Anticipation

A

Age of onset decreases w/ successive generations

Seen in several neurological disorders caused by mutations that involve expansions of trinucleotide repeats

18
Q

Hereditary haemochromatosis

A

Used by absorption of too much dietary iron –> accumulates in organs such as liver and heart
Patients have accumulated large iron stores that damage essential organs by the time they are symptomatic so patients present w/ a host of life threatening disease manifestations e.g. liver cancer

19
Q

Treatment of HH

A

Venesection

20
Q

Venesction

A

Removal of blood - done through phlebotomy needle and leg

21
Q

Causes of HH

A

Single nucleotide polymorphisms/ point mutation resulting in change in codons for AA 63 or 282

22
Q

What are recessive genetic diseases usually associated with

A

Mutations that result in loss of normal protein function

23
Q

How does the centromere divide the chromosome

A

Into the short (p) arm and the longer (q) arm

24
Q

Classification of centromeres

A

Done according to the position of the centromere and relative lengths of the p and q arms

Metacentric
Sub metacentric
Acrocentric

25
Metacentric
Centromere located midway
26
Sub metacentric
Centromeres placed slightly away from centre
27
Acrocentric
Centromere placed quite near one end of the chromosome
28
Telomere
End of chromosome
29
Isoforms
A single gene encodes for two or more isoforms through alternative splicing
30
Alternative splicing
Transcripts from coding sequences can be cut up and re-joined in many ways
31
Why can protein and transcript isoforms occur
Alternative initiation and termination sites for gene expression ---> far fewer coding-genes than potential transcripts and protein sequences
32
Why is plasticity in genome important
For tissue spp gene expression