1. The Human Genome
Chapter 14

2. Human Chromosomes
Karyotype: a picture of the chromosomes from a single cell.
Used to determine the sex, or possible genetic disorders of an individual.
44 autosomes
2 sex chromosomes

3. Determining the sex of a zygote:
Always determined by the father.
All eggs contain one X chromosome
Sperm either contain one X chromosome or one Y chromosome.

4. Pedigrees
Used to show how a particular trait is passed from one generation to the next in a family

5. Blood types
Controlled by more than one gene
A, B, O, AB
Rh factor

6. Recessive disorders most common
Genetic disorders
Recessive disorders most common
To be afflicted with a recessive disorder, one must have 2 copies of each recessive allele.

7. PKU (phenylketonuria)
The body cannot break down the amino acid phenylalanine
Nutrasweet could be deadly
If not detected early, or if a specific diet is not followed, serious brain damage can occur.
1 in 60 Caucasians are carriers of the gene that causes PKU.
The gene is found on chromosome 12

8. Tay-Sachs
Cannot break down certain fats.
Results in brain damage
The gene is found on chromosome 15
Mainly affects people of European Jewish ancestry (1 in 30 are carriers)

9. Cystic Fibrosis Affects digestive system and absorption of fats.
Causes a build up of mucus in the lungs.
CF kids are often more likely to develop pneumonia.
One of the first disorders to be actively studied for gene therapy.

10. CF (cont.) Sweat test Gene found on chromosome 7
1 in 25 people are carriers.
Most lethal autosomal recessive disorder in U.S.
No cure

11. Enzyme therapy (DNAse) Lung transplants
Treatment
Respiratory therapy
Enzyme therapy (DNAse)
Lung transplants

13. Albinism Lack of pigment in skin, hair, and eyes.
Approx. 1 in 17,000 people
Risks:
Eye problems
Severe sensitivity to sunburn.

14. Autosomal dominant disorders
Expressed when the dominant allele is present in the genotype.

15. The torso is of normal size, but arms and legs are very short.
Achondroplasia
A form of dwarfism
The torso is of normal size, but arms and legs are very short.
Average adult height of 4 feet.
1 in 25,000 births.
Gene is found on chromosome 4
“Little People”

16. Huntingtons Results in a loss of muscle control and mental function.
Breakdown of nerve cells in the brain
Approximately 1 in 10,000 births in Europe and N. America
Gene on chromosome 4
Symptoms after age 30
Autosomal Dominant

17. Marfan Syndrome
Mutation in the fibrilin gene that makes proteins found in tendons/ligaments
Results in TALL stature
Heart problems
Abe Lincoln
was suspected
to have M.S.

18. Sickle cell anemia Codominant disorder found in African Americans.
Red blood cells are misshapen.
Characterized by extreme pain in legs and arms because the cells get stuck in capillaries.
Can be fatal
The gene can prevent Malaria

19. Sickle-cell cont’d normal rbc sickle-cell rbc
Approx 1000 babies born each year
1 in 400 African Americans
Possible cure: bone-marrow transplants
Treatment:
Avoid being overly active
Watch your diet
sickle-cell rbc

20. Sex-linked genes and disorders
A situation in which an organism’s sex can affect the chances of inheriting a gene.
First studied by Morgan with fruit flies
Most sex-linked genes are found on the X chromosome

21. Recessive gene located on the X chromosome.
Color blindness gene
Recessive gene located on the X chromosome.
Men only have one X chromosome, thus only one copy of the color blind gene.

22. Color Blindness

23. Hemophilia
A disorder in which a person’s blood does not clot properly.
Gene found on X chromosome.
1 in 10,000 males born are afflicted.

24. Traditional treatment: periodic blood transfusions “Bleeder’s disease”
Hemophilia:
Main type: hemophilia a. Body cannot manufacture a specific protein needed for proper blood clotting.
Traditional treatment: periodic blood transfusions
“Bleeder’s disease”

25. Duchenne muscular dystrophy
Weakening and loss of muscle tissue.
1 out of 3000 males born in U.S.
Sex-linked/recessive
Caused by absence of dystrophin, a protein that helps keep muscle cells intact.
Genetic disorder website

26. Chromosomal disorders
loss of or gain of part or a whole chromosome.
Nondisjunction - most common chromosomal mutation.
When a gamete contains either an extra or one less chromosome.
Occurs during meiosis.

27. Down Syndrome
Also known as Trisomy 21 because of the presence of an extra chromosome 21.
Symptoms similar to mental retardation
Approx 1 in 800 babies born in U.S.
Chances of having a baby with Down Syndrome increases with the age of the mother.

28. Sex Chromosome Disorders:
Turner’s syndrome: In females, a person only inherits one X chromosome (45,X)
Klinefelter’s syndrome: In males, an extra X chromosome is present (47,XXY)

29. Hutchinson-Guilford Progeria
One mistake in the DNA sequence of the gene, LMNA causes Progeria. (point mutation)
The LMNA gene normally makes a protein called lamin A, and helps maintain the shape and function of the cell.

30. The mutation causes the gene to produce an abnormal Lamin A protein called progerin.
In children with Progeria, many cells in the body make progerin protein.
As the children age, progerin builds up in these cells causing progressive disease-Rapid aging

31. DNA analysis
Testing for alleles : makes it possible to determine if a person can pass on a particular disorder to his or her children.
DNA fingerprinting

32. Human Genome Project Began in 1990.
The goal was to analyze the entire human DNA sequence (6 billion base pairs)
Originally scheduled to be completed in 2005
In June 2003, the map was completed

33. Gene Therapy
Replacing an absent or faulty gene with a copy of a “good” or working gene.
Still considered a radical therapy.
Has not been tested thoroughly.

34. Assignment:
Page
1-10, 12,14,17,19,23,25,26,29