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Flashcards in population genetics- basics Deck (48):
1

it is clear that some diseases have a major

environmental component

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Sir William Richard Doll

british physiologist who was a pioneer in research linking smoke to health problem. He was credited for proving that smoking increased chances of lung cancer rand hear disease

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proof in pictures of disease and enviroment

twins - twin on the right smoked and sunbathed her whole life

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environmental factors

physical chemical biological

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genetic

monogenic polygenic

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how manny human diseases are caused by single gene defects

4000

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defective enzymes can have a major consequence for

metabolic pathways

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dominant

vertical pattern of individuals

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recessive

horizontal patterns of affected individuals

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autosomal recessive

consanguinity (incest) often between parents

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autosomal

males and females affected with equal probability

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X-linked recessive

ales affected, female carriers

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X linked dominant

all daughter and males are affected

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mitochondrial

non-mendelian- maternal inheritance

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Dominant diseases

achondroplasia hungtintons

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achondroplasia

dwarfism- a bone growth disorder

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Huntington's disease

neurofegenerive genetic disorder that affects muscle coordination and leads to cognitive decline and psychiatric probles

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recessive

sickle cell anaemia CF

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sickle cell anaemia

blood disorder effecting shape of the red blood cells and therefore their carry of oxygen capacity

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Cystic fibrosis

autosomal recessive disorder caused by a mutation on a cl- channel- causes thick secretion of mucous and effects the lungs and various other organs

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X-linked

duchene muscular dystrophy haemophilia

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duchess muscular dystrophy

muscle degeneration which leads to death

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hemophilia

when you can't stop bleeding

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hemophilia

when you can't stop bleeding

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common traits have a

genetic component e.g. twin, family and admixture studies indicate that type 2 diabetes and obesity have genetic components

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monozygotic twins

40% will have type 2 diabetes if one does

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dizygotic twins

around 10% will have type 2 if one does

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Linkage

generally measured from recombination frequency between two markers in crosses- but humans are not ideal organisms for genetic since scientists can't control who they breed with

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why are humans not ideal organisms for genetics

can't control who they breed with

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markers can be used to

show up genetic disorders

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markers used to show up genetic disorders

structural rearrangements SNPs RFLPs INDELs

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SNPs

single nucleotide polymorphism

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RFLPs

Restriction Fragment Length Polymorphism (RFLP) is a difference in homologous DNA sequences that can be detected by the presence of fragments of different lengths after digestion of the DNA samples in question with specific restriction endonucleases.

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linkage and statistical analysis

..

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why has there been huge process in identifying common diseased genes

because genome wide association studies mean we can study a large proportion of the common human variation in one experiment. -GWA studies empty case-control design comparing two large groups (one being affected and the other as a control) -all individuals in each group are genotyped for the majority of common known SNP --> typically around a million Association is then measured using Lod score

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Lod score

.

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pedigree symbols

.

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autosomal dominant -huntington's -polycystic kidney disease Pedigree

-every affected individual has an affected biological parent -males and females equally likely to be affected -50% chance of recurrence -normally siblings to not transmit to offspring

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autosomal recessive -CF Pedigree

-males and females are equally affected -recurrence risk of each child- 25% -traits characteristically found in siblings and not parents mating parents may be consanguineous (incest) traits may appear as an isolated event

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consanguineous

incest

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x-linked recessive -duchenne -haemophlia Pedigree

-males are much more likely to be affected -trat is never passed from rathe rot son -all affected males in a family are related through their mothers -passed from affected grandfather to carrier daughter

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mitochondrial -leber hereditary optic neuropathy

Pedigree

-non-mendelian -everyone inherits the condition through the maternal line

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complications that affect interpretation of pedigrees

1. new mutations

2.penetrance- low penetrance- sufferers would only sometimes produce the symptoms

3.expressivity- patient always expresses some the symptoms of the disease and varies from very mildly affected to very severely affected

4. delayed onset- some diseases do not express themselves until later in life, well beyond reproductive age

5. anticipating 6.imprinting

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pentrance

e.g. low penetrance- sufferers would onto sometimes produce some symptoms

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expressivity

patients always express some symptoms of the disease and varies from very mildly affected to very severely affected

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delayed onset

1. some disease do not express themselves until later life, well beyond reproductive age.

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how can diseased genes sometimes be identified

sometimes diseases will correlate with a visible chromosomal deletion or rearrangement e.g. translocation or duplication or delegation e.g. may be able to be seen on karyotypes

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example pedigree of autosomal dominant with incomplete penetrance

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