Transcript Human Genetics

Why are humans difficult to study?
Lots of chrom
Lots of genes
osomes
Small number of offspring
Pedigree Analysis
•Pedigree: family record that shows how a
several __________.
generations
trait is inherited over ________
Genetic Traits and Disorders
 Single Allele Traits
 Dominant
 Huntington’s disease: forgetfulness and irritability
& 40’s loss of muscle control, spasms, mental
in 30’s
_______;
illness, death.
dwarfism
 Achondroplasia: ____________________.
extra
fingers
and toes
 Polydactyly: ________
_____________
_________
clouding ______
lens ___
of _______;
eye
 Cataracts: _________
impaired vision, blindness.
Single Allele Traits Cont.
 Recessive




pigment of hair, skin, eyes.
Albinism: lack of _________
Cystic fibrosis: abnormal cellular secretions of thick mucus
lungs
which accumulates in the __________.
Phenylketonuria (PKU): inability to metabolize
milk
phenylalanine in ________;
PP and Pp = normal; pp = PKU
 build up causes mental retardation
 Babies tested; those w/ PKU not given phenylalanine in diet.
deterioration ___
of CNS
Tay-sachs disease: causes death by _____________
____
from lack of enzyme to breakdown fatty deposits on nerve and
brain cells.
Multiple Alleles
 Multiple Alleles: traits controlled by 3 or more alleles of
the same gene.
IA
IB and____.
i
 ABO blood groups controlled by 3 alleles: _____
_____
 Each person’s blood contains 2 of these alleles.




A type = IAi or IAIA
B type = IBi or IBIB
AB type = IAIB
O type = ii
 Which cross could result in all four blood types in the offspring?
IA
i
IB
IAIB
IBi
i
IAi
ii
Genetic Traits and Disorders
 Polygenic Traits: trait controlled by 2 or more genes
3-6
 Example: skin color is influenced by __________
genes;
controls the amount of pigment (melanin) in the skin.
 Sex-influences traits: male or female hormones may
influence gene expression.
 Example: baldness controlled by gene B; is dominant in
males but recessive in females.


BB = bald in male and female
Bb = bald in male, normal in female; caused by testosterone.
X-linked Traits
 Colorblindness: recessive; inability to distinguish
colors (red/green).
 Hemophilia: recessive, _______________
bleeding
disease;
impaired ability of blood to clot.
 Duchenne muscular dystrophy: weakens and
muscle
tissue
destroys _____________
_____________.
Non-disjunction Disorders
 Non-disjunction disorders: failure of chromosomes to
separate in meiosis.
Turner’s
 Monosomy X = _____________
syndrome:(45 chromosomes)
underdeveloped, sterile females.
 Trisomy X = XXX; super females; some retarded
 Klinefelter’s syndrome: XXY; normal egg x XY sperm

Sterile, underdeveloped males
 XYY: tall aggressive males, criminals??
 Down’s syndrome: trisomy 21
 Extra chromosome 21
 Mild to severe retardation, facial features, muscle weakness, short
Detecting Human Genetic Disorders
 Genetic screening: exam of a person’s genetic make-
up.
picture
 Ex. Karyotype = _____________
of chromosome.
 Ex. Blood test
amniotic ________
fluid
 Ex. Amniocentesis: testing of ______________
from embryo.
 Genetic counseling: informing patients about
genetic disorders and risks of having affected children.