Transcript Traits_Disorders_Teacher

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Incomplete
dominance
Intermediate in
phenotype
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Blood type co-dominance
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Genetics – Dominant
Traits, Recessive
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Hitchhiker’s Thumb
• Dominant allele –
hiker’s thumb
• Recessive – straight
thumb
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Tongue Rolling
• Ability to Roll is
dominant
• Inability to roll
is recessive
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Mid-Digital Hair
• Presence of hair
results from
dominant allele
• Absence results
from recessive allele
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Widows Peak – a dominant
trait (straight hairlines are
recessive
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Pedigree analysis
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Genetic Disorders
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(Trisomy 21) = Down’s syndrome
results from 3 copies of chromosome pair 21
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Sickle Cell Anemia
• Occurs most often in people of
African descent
• Is recessive on chromosome #11
• Abnormal blood protein changes
shape of blood cell
• Misshaped and carries less
oxygen
• Cells get less oxygen and
suffocate with this disorder
• Misshaped cells cause blocked
capillaries and arteries - often
strokes
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There is a interesting thing about sickle
cell anemia. People who carry the
tendency to have sickle cell anemia are
less likely to die from malaria. Sometimes
what is bad in one situation helps out in
another.
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Malaria is a disease caused by a
parasite that likes to set up
housekeeping in the red cells.
This parasite is carried by the
Anopheles mosquito.
Anopheles
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Albinism
• Lack of
pigmentation
• Often
sickly, tired
and/or weak
• Eyes lack
pigment and
appear red
due to blood
vessels
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Phenylketonuria (PKU)
• Enzyme missing to break down the
amino acid phenylalanine
• Child usually does not survive long 
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Tay Sachs Disease
• Harmful fatty acids
produced in brain of a
developing child
• Enzymes not produced to
reduce levels
• Nerve cells are injured by
the fatty acids
• Characteristic cherry red
spot in the eye develops
• No cure
• Death occurs by age 5 on
average 
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Colorblindness
If Mom has it, all her sons will
and girls have a 50:50 chance of getting it
Colorblind
Okay
Punnett Xc
Square
X
Y
Xc X
XcY
Mom: Xc Xc
Dad: XY
Xc
Xc X
XcY
All daughters are carriers, but with one
working X, they do not show
colorblineness
All sons colorblind – boo hoo, sniff,
sniff
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Take the Test
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Colorblindness Gene is located on the X-Chromosome. Use
of a Pedigree to Track Transmission
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Testing for Genetic
Disorders
Karyotyping – picturing
human chromosomes
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Fetal Diagnosis for Genetic Problems –
Amniocentesis & the Needle of Doom
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Overall
lessons:
Overall Lessons
about
Genetics
1. Your overall phenotype is controlled thousands of separated
genes.
2. Some alleles are co-dominant so there can be more than two
phenotypes per gene.
3. Genetics is never simple! – it becomes complicated when more
than one gene is involved in producing a phenotype (Green eyes
for ex.)
4. Pedigree analysis can help one determine human genotypes.
5. Harmful recessive genetic traits can persist in the population
through carriers
6. Genetic testing will become more widespread.
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7. Not all genetically-caused disorders are inherited. Some are
caused by mutation of your genes by chemicals or radiation.