1. Understanding heredity
Part 2

2. mutations

3. Mutations Genes code for proteins
Mistakes in genetic code cause mistakes in the protein
Mutations are mistakes in genetic code
A point mutation involves one nitrogen base in a codon
Some point mutations cause no difference in protein produced
Others point mutations can cause a noticeable or serious effect

4. Mutations, cont. Types of Point Mutations:
Substitution – one nucleotide is changed to another
Example: CAT GCA CAG GCA
Insertion – one nucleotide is inserted into a sequence
Example: CAT GCA CAG TGC A
Deletion – one nucleotide is deleted from a sequence
Example: CAT GCA CAG CA

5. Mutations, cont. Substitutions usually affect only one amino acid
Insertions or deletions can result in a frameshift mutation – they shift the “reading frame” of the bases
This can change every amino acid that follows the point of mutation

6. Mutations, cont.
Chromosomal mutations – involve changes in the number or structure of chromosomes
Some may change the locations of genes on chromosomes
Others may change the number of copies of a gene made

7. Mutations, cont. Types of Chromosomal Mutations:
Deletion – an entire gene is deleted
Duplication – an extra copy of the gene is added
Inversion – a segment of the chromosome is flipped over
Translocation – a portion of a chromosome breaks off and reattaches to another chromosome

8. Mutations,cont.
Many mutations are neutral – they have little/no effect on the expression of genes or the function of proteins for which they code
Some mutations can result in the production of defective proteins that disrupt normal biological activities
Harmful disruptions cause many genetic disorders
Beneficial disruptions can be the source of genetic variation that allows certain members of a species to be more successful in a changing environment

9. Mutations, cont.
Polyploidy – condition in which an organism has an extra set of chromosomes
Occurs during meiosis when the chromosomes fail to separate
Triploid- 3N
Tetraploid- 4N
In animals: polyploidy is deadly
In plants:
benefits – larger, stronger; source of seedless fruits
drawbacks – cannot be fertilized; have to purchase seed to make more plants

10. Genetic disorders

11. Genetic Disorders
Genetic disorder – disease caused by an abnormality in the organism’s DNA
Single-gene disorders are inherited in Mendelian patterns:
Autosomal recessive disorders
Autosomal dominant disorders
Sex-linked patterns

12. Genetic Disorders, cont.
Autosomal Recessive Disorders:
Most human genetic disorders are caused by recessive alleles on autosomes
This means the individual must inherit two copies of the recessive allele
Examples:
Sickle-cell Disease – red blood cells develop a rigid sickle shape; blood cells clot and cause oxygen loss to body cells
Cystic Fibrosis – thick mucus secretions in lung, pancreas, liver and intestines
Tay-Sachs Disease – progressive degeneration of all nerve cells starting about 6 months old with death by 4

13. Genetic Disorders, cont.
2. Autosomal Dominant Disorders:
Less common than recessive because they are often lethal
In most cases, individuals with disorder live long enough to reproduce
Keeps allele in population
Examples: Huntington’s Disease & Marfan Syndrome

14. Huntington’s Disease –
degeneration of nerves
affects muscle coordination
causes mental and emotional decline
starts in mid-life
most common cause of death is pneumonia; second most common is suicide

15. Marfan Syndrome -
affects proper growth of connective tissue
individuals are unusually tall, with long & thin limbs/toes/fingers
disruption of proper heart function is most serious complication

16. Genetic Disorders, cont.
Sex-Linked Patterns
Females: XX Males: XY
Y chromosome contains the gene, SRY, that codes for development of the testes
If testes form, other genes guide production of testosterone and fetus develops into a male
If Y chromosome is absent or SRY gene does not function correctly, fetus develops into a female

17. Genetic Disorders, cont.
Genes located on sex chromosomes are called sex-linked genes
Many genes are found on the X chromosome, but not the Y chromosome
Because there is not an alternate allele on the Y chromosome, the allele on the X is the one expressed
Sex-linked = X-linked
Examples of X-linked disorders:
Color blindness – inability to see some, or all, colors in the normal way
Hemophilia – blood disorder in which blood does not clot properly (have low to no clotting factor in blood)

18. Pedigree Chart – Queen Victoria of England (died 1901)
Died: 1945, no children

19. biotechnology

20. Biotechnology
Biotechnology – use of living organisms to improve the quality of human life

21. Biotechnology, cont.
Bacteria are the most commonly used organisms in biotechnology
This is because their DNA is not surrounded by a nucleus and is easier to manipulate
Also, manipulated bacteria reproduce rapidly
Insulin, produced by E.coli bacteria, is the first protein commercially manufactured using this method

22. Biotechnology, cont. Human DNA is 99.9% identical
The .1% difference is displayed in fingerprints, inherited health conditions and appearance
Gel electrophoresis is a process used by scientists to isolate and study specific proteins
This increases our understanding about how proteins work and how we can utilize them to a better quality of life