1. DNA Mutations & Disorders

2. Normal Protein Formation
A segment of DNA strand is copied by mRNA in the nucleus.
mRNA leaves nucleus and goes to ribosome in cytoplasm.
Ribosome “reads” mRNA and calls for specific amino acids.
Amino acids linked together to form protein chain.

3. Abnormal Protein Formation
Mutations in DNA will code for wrong amino acids which will cause wrong protein to form.
Can lead to cell death, disease, disorders

4. What is a mutation? Any change in a gene or chromosome.
Most are natural and have no effect on the organism- can promote good genetic diversity
Some are harmful
Some are lethal (cause death in offspring)
Some are good for the organism (ex: some mosquitoes have a gene mutation that makes them resistant to pesticide- leads to evolution of stronger mosquito populations)

5. What are some types of mutations?
Point mutation- change in ONE single nitrogen base in ONE gene.
This change causes the code to change so amino acids are not put in correct order.
EX: albinism, sickle cell anemia

6. Types of Point Mutations
A. Silent- one letter change but no change in amino acid= no change in protein structure= no problems
B. Missense- one letter change causes changed amino acid= wrong protein structure
C. Nonsense- one letter change causes STOP codon in middle of amino acid chain= protein won’t get made
(Normal)

7. What are some types of mutations?
2. Chromosome Mutations (Frameshift)- changes in MANY genes, entire segments of chromosome are messed up.
Because more genes are involved, usually more harmful to the organism.

8. Deletion- part of chromosome is lost
Duplication- part of chromosome is repeated twice
Inversion- chromosome breaks, piece is turned over & reinserted upside down
Translocation- two chromosomes affected- one piece detaches & reattaches to another chromosome A B C D

9. E. Insertion- a nitrogen base is added which causes nitrogen bases to shift to the right, throws off amino acid sequence.
F. Nondisjunction- a chromosome pair fails to separate properly during meiosis (some sperm/egg get too many chromosomes, some get too few).
Monosomy- too few (45 chromosomes)
Trisomy- too many (47 chromosomes)

10. What are some causes of mutations?
1. Mutagen- anything that causes a mutation in DNA in a cell.
UV light
Radiation
X rays
chemicals in tobacco smoke, synthetic materials, pollution
viruses

11. What is the difference between germ cell mutation & somatic cell mutation?
Occurs in gametes (sperm/egg)
Does not affect individual person
CAN be passed to offspring
Somatic Cell mutation
Occurs in body cells
Affects individual in which it occurs
CANNOT be passed to offspring
If occurs in genes that control cell reproduction can become CANCER.

12. What are some methods of detection?
Ultrasound- sound waves generate image of unborn child. Detect abnormalities of limbs, organs, etc.

13. What are some methods of detection?
Amniocentesis: use needle to extract fluid/cells surrounding the fetus. Chromosomes can then be karyotyped

14. What are some methods of detection?
Karyotyping: pictures of chromosomes are matched up according to size

15. Difference between Autosomes & Sex Chromosomes
Autosomes- first 22 pairs of chromosomes in karyotype
Sex Chromosomes- last pair of chromosomes that determine gender
Male karyotype- sex chromosomes are a big chromosome (X) and a small chromosome (y)
Female karyotype- sex chromosomes are two big chromosomes (XX)

16. What are some types of genetic disorders
1. Autosomal Dominant- if dominant gene is present, person will have disorder
Huntington’s disease
Achondroplasia

17. HUNTINGTON’S DISEASE Caused by dominant allele Develops after age 30
Lose muscle control, mental deterioration, & eventually death.
No cure

18. Achondroplasia Dwarfism
Defect in gene that controls cartilage formation
Shortened stature
Some have normal sized torso but shortened limbs.

19. What are some types of genetic disorders?
2. Autosomal Recessive- must have two recessive genes to show disorder
Phenylketonuria
Cystic Fibrosis
Tay-Sachs
Sickle cell anemia

20. PHENYLKETONURIA Also called PKU
Must inherit two recessive alleles to show this disease.
Unable to synthesize the enzyme that breaks down the amino acid phenylalanine. Phenylalanine accumulates and kills brain cells.
Tested at birth- if present, put on diet low in phenylalanine (no milk) for first six years to prevent brain damage.

21. CYSTIC FIBROSIS Also called CF Caused by a recessive allele
on chromosome #7.
Serious digestive problems, thick mucus that clogs lungs. Makes breathing & digesting food very difficult.

22. TAY-SACHS DISEASE Caused by two recessive alleles
Occurs mostly in Jewish families
Fats accumulate in brain cells, mental deficiency, delayed development, blindness
Usually results in death within first few years of life.

23. SICKLE-CELL ANEMIA
Red blood cells are half moon shaped instead of round.
Clog blood vessels, depriving tissues of oxygen- causes severe pain, weakness.
Found more often in people of African descent.

24. What are some types of genetic disorders?
3. Sex-Linked- disorder on sex chromosomes
Klinefelters syndrome
Turner’s syndrome
XYY males

25. KLINEFELTERS SYNDROME
Males with an extra X chromosome
XXY
Sterile
Some degree of mental deficiency

26. TURNER’S SYNDROME Females with only one X chromosome. XO Sterile
Short, with thick, webbed necks, mild mental deficiency.

27. XYY MALES Males with extra Y chromosome taller than average
Produce more testosterone, some say more aggressive