Lecture 1 Flashcards by Bella Parolini

How many base pairs in human DNA

3.12 billion

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How many genes in human genome

25000

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What percent of DNA is the same between people

99.5%

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Do all cells in the body have the same DNA

Yes, but different genes are expressed in different cells

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How is variation in the human genome generated

mutations and SNPs

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SNP

single nucleotide polymorphism
-change in a single base pair
-can result in non change or a big change

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Hereditary

come from parents, familial

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congenital

present from birth

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are all genetic disorders congenital?

No, ex. Huntington’s Disease

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are all congenital diseases genetic?

no, ex. HIV

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3 classifications of human genetic disorders

Disorders related to mutations in single genes (Mendelian disorders)
Complex Multigenic Disorders
Chromosomal disorders

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Disorders related to mutations in single genes

Mendelian disorders
Result from mutations in single gene resulting in large effects
Pretty rate

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Complex Multigenic Disorders

More common
Interaction between a number of genes

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Genetic heterogeneity

Mutations in several locations have impact on same trait/disorder

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Chromosomal disorders

Structural (insertions, deletions) or numerical changes (i.e. less chromosomes) in autosome or sex chromosomes
Not very common

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3 transmission patters for Mendelian disorders

Autosomal dominant disorders
Autosomal recessive disorders
X-linked disorders

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Autosomal dominant disorders are evident in which state

heterozygous state (only one allele needs to have mutation)

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Penetrance

Probability of a gene or genetic trait being expressed
100% penetrance = every individual with mutation shows phenotype

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Expressivity

The degree to which a phenotype is expressed by individuals who have a particular genotype (“severity” of phenotype)

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Which category of mendelian disorders is the most common

Autosomal recessive

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Autosomal recessive disorders are evident in which state

homozygous (both alleles need to be present)

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Penetrance and expressivity in autosomal recessive disorders

-Complete penetrance common
-Expressivity more uniform

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When is onset for autosomal recessive disoders

early in life

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All sex-linked disorders are:

X-linked

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Most X-linked disorders are dominant or recessive?

Recessive

Which sex is more affected by X-linked disorders and why

Males, they are hemizygous for X-linked genes (only have one copy)

3 mendelian disorders from mutations in structural proteins

-Marfan Syndrome -Ehlers Danlos Syndrome -Sickle Cell

6 mendelian disorders from mutation in enzymes

-lysosomal storage disorder -tay-sachs disease -gaucher disease -Nieman pick disease -pompe disease -hemophilia

3 mendelian disorders from mutations in receptor and transport system

-familia hypercholesterolemia -cystic fibrosis -achondroplasia

Collagen

-glue that holds everything together -abundant in connective tissue

What does collage provide

tensile strength (max stress a tissue can sustain)

how is tensile strength generated

fibril formation

EDS category

mutation of structural protein

Ehlers Danlos Syndrome cause

mutation of collagen V

Ehlers danlos syndrome symptoms

-joint hypermobility, stretchy skin, arthritis, etc. (broad implications bc collagen is abundant)

Vascular EDS

-more severe -can lead to rupture of blood vessels

Sickle cell disease category

mutation of structural protein

sickle cell disease cause

mutation in hemoglobin gene (HBB)

most common form of sickle cell disease

sickle cell anemia (cells rigid and sickle shaped)

sickle cell disease vs trait

-disease: both alleles affected -trait: one one allege for abnormal hemoglobin

is sickle cell trait harmful

generally benign

when might sickle cell trait be harmful

dehydration, low oxygen levels, high altitude

sickle cell trait advantages

survival against malaria

lysosome mutations category

enzymes

inclusion cell disease

lysosomes do not get enzymes due to defect in manos-6-phosphate group

manos-6-phosphate group

"address label" for lysosomal proteins

lysosomal storage disorders general

rare symptoms include delays, seizures, dementia, blindness, deafness no cures

tay-sachs disease

lysosomal storage disease

tay-sachs disease cause

-mutations in HEXA gene (hexosaminidase A) -enzyme that degrades gangliosides (food source) in brain cells -gangliosides accumulate in brain and choke off cells

signs of tay-sachs disease

-manifest around 6months -motor and mental deteroration -2-3 year life expectancy

pompe disease category

-lysosomal storage disorder -enzyme class

other name for pompe disease

glycogen storage disease type II

cause of pompe disease

enzyme deficiency acid alpha-glucosidase accumulation of glycogen (instead of cleaved to glucose) leads to damage of muscle cells and organs

onset of pompe disease

-infantile onset: cardiomedaly (enlarged heart) -late onset: does not affect heart, progressive muscle weakness

pompe disease treatment

-symptom management -enzyme replacement therapy: myozyme

hemophilia disorder category

enzyme disorder

hemophilia general

blood clotting disorder, sex-linked x chromosome

2 types of hemophilia

A and B

hemophilia a

clotting factor VIII deficiency

hemophilia b

factor IX deficiency

hemophilia symptoms

prolonged bleeding or oozing, sometimes in response to minor trauma or spontaneous

hemophilia treatment

liver transplant = cure manage with clotting factor therapy

what can clotting factor therapy lead to

Abs made to infused clotting factors, need more and more factor injected

what is cholesterol

waxy, white substance highly produced in liver get some from food

cholesterol function

lipoproteins: cell wall, production of hormones

types of cholesterol

LDL (bad) and HDL (good)

familial hypercholesterolemia category

receptors

familial hypercholesterolemia cause

defect in gene encoding LDL-R (bad) on chromosome 19 -typically negative feedback to slow down cholesterol synthesis, but this causes cells to keep making more and more LDL

symptoms of familial hypercholesterolemia

deposits of fatty skin (xanthomas) and xanthelasmas (on eyelids) chest pain and heart disease (cholesterol clogs arteries)

what is the most frequent disorder of mendelian inheritance

heterozygous vs homozygous FH

homozygous = 5 to 6 fold increase in blood cholesterol (less for heterozygous)

FH treatment optioonos

statins diet

Statins

treat FH -bind to enzyme that produces chol. and blocks it to reduce amount of chol made

Fibroblast growth factor receptor (FGFR) mutations category

receptor

examples of FGFR

achondroplasia and thanatophoric displasia

achondroplasia

mutation that leads to dwarfism results in abnormal cartilage formation and growth plate problems causes constitutive activation

thanatophoric displasia

homozygous, more severe/death

FGFR mostly inherited or random

random

achondroplasia treatment

NOT growth hormone limb lengthening but high complications