Transcript Genetics and Genetic Diseases

Genetics and Genetic
Diseases
Genetics
Study of inheritance and human disease
 1860’s – Gregor Mendel
 Gene = DNA  RNA Proteins (enzymes)
 permit specific biochemical reactions to
occur
 Genes determine the structure and
function of the human body
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Chromosome
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Chromosomes are made of chromatin
(DNA)
Human Genome Project
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Genome – entire collection of genetic
material in a cell
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2001 – rough draft published
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30,000 genes
1% carries genes, rest is filler
Genomics – analysis of genome
 Proteomics – proteins encoded by genes,
goal is to understand role of each protein
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Ideogram
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Simple cartoon of chromosome
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P-arm – shorter segment
Q – arm – longer segment
Bands – show landmarks
Chromosomes
46 chromosomes in a cell, 23 pair
 22 pair – autosomes (body cells)
 23rd pair – sex chromosomes
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XX, XY
Undergo meiosis, produce sex cells (gametes)
Sperm meets egg = zygote
Genetic Variation
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Independent assortment
Crossing over
 Random
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fertilization
Gene Expression – Mendel
Complete Dominance
Dominant – CC, trait seen
 Recessive – cc, trait only seen if both
alleles are recessive
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CC – homozygous dominant
 Cc – heterozygous
 cc – homozygous recessive
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Example: Albinism
Gene expression
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Codominance – both alleles are dominant
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Incomplete dominance – hybrid
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Ex – blood type A, B, O, AB
Pink flowers
Sex linked – non-sexual trait carried on X
or Y chromosome, sometimes called xlinked since X chromosome is largest
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Hemophilia, color blindness
Genetic Mutations
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Change in DNA, genetic code
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Can occur spontaneously
Mutagens – cause mutations
Carcinogens – cause cancer, viruses
Damage to chromosome, deletion
can be beneficial
Mitochondrial DNA
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Powerhouse of cell with own circle of DNA
Inheritance occurs only through the mother
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sperm mitochondria do not
survive during fertilization
Codes for only a few
important enzymes
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carry mutations that
produce disease
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Leber’s hereditary optic neuropathy
Parkinsons
Alzheimers
Mechanisms of Genetic Disease
Single gene diseases
 Genetic predisposition – not solely caused
by inheritance, but environmental
 Non-disjunction – failure of chromosomes
to separate
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Trisomy – triplet of chromosomes (Down
syndrome)
Monosomy – single chromosome only (Turner
syndrome)
Single gene diseases
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Cystic fibrosis
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Recessive
Chromosome 7
CFTR gene regulates transfer of sodium ions
across cell membrane and serves as chloride
ion channel
Phenylketonuria - PKU
Recessive
 Fail to produce enzyme phenylalanine
hydroxylase
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Converts aa phenylalanine into tyrosine
Lack of enzyme results in accumulation and
presence of phenylketone in urine which
destroys brain tissue.
Identified at birth
Diet restrictions
Chromosomal diseases
Down syndrome, Trisomy 21
 Not inherited, result of nondisjunction
 Characterized by
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Varying range of mental retardation
Distinctive facial appearance
Enlarged tongue…
Klinefelter syndrome
Nondisjunction of sec chromosomes – XXY
 Characteristics
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Long legs
Enlarged breasts
Low intelligence…
Turner Syndrome
XO, monosomy female
 Characteristics include:
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failure of sex organs maturing
dwarfism or short stature
cardiovascular defects…
Can be treated with hormone therapy,
surgery
Prevention and treatment
of genetic diseases
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Genetic counseling – professional
consultation
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Help to determine risk
Help evaluate whether offspring have a genetic
disorder
Offer advice on treatment, care
Tools
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Pedigree
Punnett square
karyotype
Pedigree
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Shows relationships in a family over
several generations
Punnett square
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Box used to determine the probability of
inheriting genetic traits
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Monohybrid
dihybrid
Karyotype
Used to find chromosomal disorders
 Use a sample of cells (cheek, wbc)
 Cells in metaphase are stained and
photographed
 Chromosomes cut and
arranged according to size
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Amniocentesis
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Fetal cells floating in amniotic fluid are
collected using a LARGE syringe
Chorionic Villus Sampling
Cell from chorionic villi are collected from
area surrounding embryo
 Cells are grown in petri dishes, then
analyzed
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Treating Genetic Diseases
No cure, but some can treat symptoms
 Gene therapy
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Gene replacement – replace abnormal with
normal
Gene augmentation – normal cells are
introduced and add normal proteins