Understanding heredity

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