Biochem Genetics - Firstaid

Front 1

Codominance

Back 1

Neither of two alleles is DOMINANT

Front 2

Example of codominance

Back 2

Blood group antigens - A/B are both dominant

Front 3

Variable expression

Back 3

Nature and severity of the phenotype varies from one individual to the next

Front 4

Incomplete Penetrance

Back 4

Not all individuals with a mutant GENOTYPE show the mutant PHENOTYPE

Front 5

Pleotropy

Back 5

1 Gene has >1 effects on an individual's phenotype

Front 6

Imprinting

Back 6

Differences in phenotype depending on whether the mutation is of MATERNAL vs PATERNAL origin

Front 7

2 diseases of Imprinting:
What is the origin?

Back 7

Angelman's - MATERNAL

Prader willi - PATERNAL

Front 8

Anticipation

Back 8

Severity of disease worsens OR Age of Onset gets earlier in succeeding generations

Front 9

Example of a disease that shows Anticipation:

Back 9

Huntington's chorea

Front 10

Loss of heterozygosity:

Back 10

When a patient has one abnormal allele of a tumor suppressor gene, and then LOSES HETEROZYGOSITY due to another mutation in somatic DNA

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Result of LOH:

Back 11

Cancer

Front 12

What does NOT show LOH?

Back 12

Oncogenes - activation of only one can cause cancer.

Front 13

Dominant Negative Mutation

Back 13

When a heterozygote produces an abnormal gene product that in turn inhibits the function of the NORMAL product from the nonmutant allele.

Front 14

So a dominant negative mutation is _____ despite being heterozygous:

Back 14

Looks homozygous

Front 15

Linkage Disequilibrium:

Back 15

Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance

Front 16

How is Linkage disequilibrium measured? What does it often show?

Back 16

-Msr in population NOT family
-Often shows variation between populations

Front 17

Mosaicism

Back 17

When cells in the body have different genetic makeups - so there are 2 different cell populations

Front 18

Example of how mosaicism develops:

Back 18

Lyonization - random X inactivation in females

Front 19

Locus heterogeneity:

Back 19

Mutations at different loci can produce the SAME phenotype

Front 20

Example of locus heterogeneity:

Back 20

Albinism

Front 21

What are Hardy Weinberg population genetics FOR?

Back 21

Measuring the prevalence of a DISEASE and an ALLELE in a population

Front 22

4 assumptions of Hardy weinberg equilibrium:

Back 22

-No mutation is occurring
-Mating is random
-No migration of alleles into or out of population measured
-No selection for genotypes

Front 23

Equation for DISEASE prevalence:

Back 23

P2 + 2pq + q2 = 1

Front 24

What is P? What is Q? What is 2PQ?

Back 24

p = a separate allele prev
q = a separate allele prev
2pq = heterozygote prevalence

Front 25

Equation for ALLELE prevalence:

Back 25

p + q = 1

Front 26

What is Imprinting?

Back 26

When at a single locus only ONE allele is active and the other is INACTIVE.

Front 27

How does Imprinting happen?

Back 27

By methylation

Front 28

What if the ACTIVE gene is deleted?

Back 28

Disease

Front 29

What are the 2 diseases of Genomic Imprinting?

Back 29

Prader Willi
Angelman's syndrome

Front 30

What is deleted in Prader Willi?

Back 30

The normally active paternal gene

Front 31

What are the 4 clinical manifestations of Prader Willi?

Back 31

-Hypogonadism
-Obesity
-Mental retardation
-Hypotonia

Front 32

What is deleted in Angelman's syndrome?

Back 32

The normally active MATERNAL allele

Front 33

What are the 4 clinical manifestations of Angelman's syndrome?

Back 33

-Seizures
-Ataxia
-Mental retardation
-Inappropriate laughter (happy puppet)

Front 34

When do autosomal dominant disease tend to present?

Back 34

Later - after puberty

Front 35

What ARE autosomal dominant disease often? What sex can be affected?

Back 35

Structural gene defects
Either sex

Front 36

When are autosomal RECESSIVE disesaes tend to present?

Back 36

In CHILDHOOD

Front 37

What ARE auto recessive diseases often, and what sex gets it?

Back 37

METABOLIC ENZYME defects - either sex

Front 38

What tends to be more severe; autosomal recessive, or dominant?

Back 38

Auto RECESSIVE

Front 39

What tends to affect multiple successive generations; auto dom or recessive?

Back 39

DOMINANT - for an auto recessive disease to show up requires both parents being pos for the allele which is rare unless siblings!

Front 40

What sex is an X-linked Recessive disorder going to be more severe in?

Back 40

Males - they have a 50% chance of being affected when their mother has the allele.

Front 41

What sons will be affected if their father carries an X-linked recessive gene defect?

Back 41

NONE - males only inherit the Y chromosome from their dad.

Front 42

What are the hallmarks of X-linked DOMINANT inheritance?

Back 42

-Either m/f offspring of a carrier mother may be affected
-ALL female offspring of a father will be affected.

Front 43

What is an example of an X-linked DOMINANT disease?

Back 43

Hypophosphatemic Ricket's

Front 44

How are Mitochondrial enzyme disorders transmitted?

Back 44

Through MOTHER genes only

Front 45

What sex can be affected by Mitochondrial enzyme disorders inherited from maternal DNA?

Back 45

Either sex - sons or daughters

Front 46

3 examples of mitochondrial DNA diseases:

Back 46

-Leigh's disease (Subacute NEM)
-Mitochondrial Myopathies
-Leber's hereditary optic neuropathy