exam 3 quiz 3 biochem

Which cells are diploid

Somatic cells

Which cells are haploid

Gametes

Single gene disorders

Monogenic, single gene pair, autosomal or X-linked

Chromosomal abnormalities

Altered structure or number

Multifactorial traits

Combo of genetic and environmental influences

All tumor suppressor gene mutations are

Autosomal dominant

Hereditary chance of passing on an autosomal dominant trait

50%

Loss of function mutations (dominant)

Defects in structural proteins or regulatory proteins

Haploinsufficiency and an example

1 copy not enough, familial hypercholesterolemia

Hereditary chance of passing on autosomal recessive traits

25%

Catalytic proteins and incest usually lead to

Autosomal recessive mutations

Adult hemoglobin

HbA (2 a 2 B)

Fetal hemoglobin

HbF (2 a 2 y)

How many alpha hemoglobin copies

4

How many beta hemoglobin copies

2

A-thalassemia missing 1 copy

Silent carrier, normal

A-thalassemia Missing 2 copies

Trait, like B-minor

A-thalassemia missing 3 copies

HbH disease, like B-intermedia

A-thalassemia Missing all 4 copies

Hydrops fetalis

Which disease is Hb BART associated with

Alpha thalassemia

What causes symptoms in beta thalassemia

Increased insoluble A hemoglobin that prevents RBC production and low normal hemoglobin

Minor B thalassemia

1 normal, 1 mutant

Major B thalassemia

2 mutants, skeletal deformities

Neurofibromatosis type 1

Autosomal dominant, mutation in regulatory NF1 gene

Marfan syndrome

Autosomal dominant, defect in FBN-1 gene that encodes fibrillin

Achondroplasia

Autosomal dominant, mutation in FGFR3 gene receptor

Thalassemias

Autosomal recessive

Symptoms of NF1

Cafe spots, neurofibromas, axillary freckling, and Lisch nodules

Types of achondroplasia

1 copy: little person

2 copies: death in infancy

Point mutation

transition (purine to purine) or transversion (purine to pyrimidine)

Silent mutation

One codon change, AA stays the same

Missense mutation

Codon and AA change

Conservative missense mutation

Similar AA (like two polar)

Nonsense mutation

Early stop codon

Nonstop mutation

Changes stop codon to normal codon

Insertions and deletions

Frameshift: not a 3

In-frame: 3, full AA inserted or deleted

Trinucleotide repeat expansion mutations

Amplifies repeated bases, faulty protein in coding region, low production/toxicity in UTR

Splice mutations

Removing exons or leaving introns

Large segment mutations

Incorrect recomb or unequal crossover in meiosis

Polymorphisms

Frequency of 1% or more

Sickle cell

Missense mutation in Bs-globin gene

PKU

Nonsense mutation in phenylalanine hydroxylase gene

Renal cell carcinoma

Nonstop mutation in BRCA-1 or Von-Hip

Duchennes muscular dystrophy

Frameshift mutation

Becker muscular dystrophy

In-frame mutation

Cystic fibrosis

In-frame mutation in coding region

Fragile X syndrome

RE in 5’ UTR of FMR1 gene

Myotonic dystrophy

RE in 3’ UTR of DMPK gene

Friedreichs Ataxia

RE in intron of frataxin

Huntington’s

RE in coding region of HTT

B-thalassemia mutation

Splicing in promoter

Variable expression

NF type 1

Pleiotropy

Marfan syndrome, 1 mutation affects multiple systems

Germline Mosaicism

Type 2 OI (new mutation of autosomal dominant)

Reduced Penetrance

Retinoblastoma, requires 2 events

Delayed age of onset examples

Huntingtons and myotonic dystrophy

Locus heterogeneity

Same phenotype, diff mutation loci/ gene (EDS)

Anticipation

each generation gets longer RE and earlier onset and worse symptoms

Genetic drift

Rare genes in one population (MSUD)

Gene flow

Exchange of genes between populations

Consanguinity

Incest, siblings have 50% same genes

Methemoglobinemia

Congenital or from nitrates, chocolate blood and blue skin

Von-Hippel Lindau

Autosomal dominant defect in HDL tumor suppressor gene, causes pehochromo

Pheochromocytomas

Tumor of adrenal glands (Von-Hip)

X-linked dominant

Rare, usually females because males die

Examples of X-linked dominant

Rett syndrome and hypo ricketts

X-linked

Mainly males, mother is carrier, no male to male transmission

Hemizygous

Males for X

Hemophilia A + B

X-linked, mutation of clotting factors 8 or 9

Duchenne muscular dystrophy

X-linked, defect in dystrophin, more common, more severe

Becker muscular dystrophy

X-linked, defect in dystrophin, less common, milder

X inactivation

Barr body is inactive X, Xist is transcribed on inactive X

Fragile X syndrome

X-linked, not dominant or recessive, more in males, less severe in females

Mitochondrial inheritance

All offspring from affected mother, heteroplasmy from # of mtDNA copies

3 mitochondrial inheritance examples

Leber, MERFF, MELAS

Nondisjunction

Failure of chromosomes to separate, usually in meiosis 1

Down syndrome

Trisomy 21

Edward’s syndrome

Trisomy 18

Patau syndrome

Trisomy 13

Klinefelter syndrome

XXY (males)

Turner Syndrome

X (webbed neck)

Jacob’s syndrome

XYY (tall, acne)

Triple X

XXX (x inactivation provides balance)

Multifactorial inheritance deals with what

Polygenic traits (combined activity of several genes)

Relative risk ratio for disease

Prevalence in relatives / in general population

What traits follow a bell curve

BP, head size, height, IQ, skin color

What traits do not follow a bell curve

Diseases

Liability/ threshold model

Must cross threshold of liability to express disease, lower threshold is higher prevalence

Recurrence risk

Likelihood of disease in an individual after a relative presents affected

Heritability

Amount of a condition that’s determined by genes

Regression to the mean

Children will get closer to average if parents are both very far from mean