1
2
Incomplete dominance
Intermediate in phenotype
3
Blood type co-dominance
4 6
4
5
6
Genetics – Dominant Traits,
Recessive
7
Hitchhiker’s Thumb
• Dominant allele – hiker’s thumb
• Recessive – straight thumb
8
Tongue Rolling
• Ability to Roll is dominant
• Inability to roll is recessive
9
Mid-Digital Hair
• Presence of hair results from dominant allele
• Absence results from recessive allele
10
Widows Peak – a dominant trait (straight hairlines are recessive
11
Pedigree analysis
12
Genetic Disorders
13
(Trisomy 21) = Down’s syndrome results from 3 copies of chromosome pair
21
14
15
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
16
17
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.
18
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
19
Albinism
• Lack of pigmentation
• Often sickly, tired and/or weak
• Eyes lack pigment and appear red due to blood vessels
20
Phenylketonuria (PKU)• Enzyme missing to break down the
amino acid phenylalanine
• Child usually does not survive long
21
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
22
ColorblindnessIf Mom has it, all her sons will
and girls have a 50:50 chance of getting it
PunnettSquare
Xc Xc
X Xc X Xc X
Y XcY XcY
All daughters are carriers, but with one working X, they do not show colorblineness
All sons colorblind – boo hoo, sniff, sniff
Colorblind Mom: Xc XcOkay Dad: XY
23
Take the Test
24
25
26
27
28
Colorblindness Gene is located on the X-Chromosome. Use of a Pedigree to Track
Transmission
29
Testing for Genetic Disorders
Karyotyping – picturing human chromosomes
30
Fetal Diagnosis for Genetic Problems – Amniocentesis & the
Needle of Doom
31
Overall lessons:
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.
7. Not all genetically-caused disorders are inherited. Some are caused by mutation of your genes by chemicals or radiation.
Overall Lessons about Genetics