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UNIT IV

UNIT IV. Genetics. Chapter 10 Patterns of Inheritance. Genetics A. Mendel – father of genetics Inheritance – traits carried on chromosomes Genes – code for certain traits Alleles – same gene, different trait. B. Principle of dominance – dominant trait will express itself.

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UNIT IV

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  1. UNIT IV Genetics

  2. Chapter 10 Patterns of Inheritance

  3. Genetics • A. Mendel – father of genetics • Inheritance – traits carried on chromosomes • Genes – code for certain traits • Alleles – same gene, different trait

  4. B. Principle of dominance – dominant trait will express itself • Dominant traits – expresses , shows up • Recessive traits – will only show up if both recessive alleles are present

  5. C. Genotype – gene, “code” • R = red & r = white • 1. Homozygous dominant – 2 dominant alleles (RR = purebred) • 2. Homozygous recessive – 2 recessive alleles (rr = purebred) • 3. Heterozygous – one dominant and one recessive allele (Rr = hybrid) • D. Phenotype – how genotype expresses itself , “looks like

  6. Punnett square – prediction of pairing • R = red, r = white • Genotypes all Rr • Phenotypes all red • RR x rr R R RrRr RrRr r Heterozygous(hybrid) cross r • R = red, r = white • Genotypes 1 RR, 2 Rr, 1 rr • Phenotypes 3 red, 1 white • Rr x Rr R r R r

  7. Incomplete dominance – heterozygous “blending” of dominant and recessive trait • Genotypes all Rr phenotypes all pink • RR x rr • 1RR = red, 2Rr = pink, 1 rr = white • 2 pink and 2 white R R r r R r R r R r r r

  8. Codominance – if heterozygous, both traits are expressed • Blood types : antigens A, B, AB, O • AB blood - both A and B antigens are present • Positive blood is a separate gene Rh d antigen

  9. F.Multiple alleles – traits expressed on more than two alleles • 3 or more alleles – combinations of alleles  genotype AABBCCDD whats the phenotype • Human examples • Hair color – 3 alleles (9) • Eye color – 3 alleles (9) • Skin color – 8 alleles (64)

  10. Polygenic system – interaction of multiple genes, determines phenotype • Continuous variation – full range of phenotypes – • Discontinuous variation – phenotype fall into a few well separated categories

  11. H. Environmental Influence on gene expression • 1. sun exposure, cold • example: siamese cat and himalayan darker color on ears, face and paws

  12. I. Principle of segregation • Gametes – separation of alleles – occurs during meiosis • Parental – purebreds homozygous, dominant or recessive (RR x RR or rr x rr) P generation = RR x rr • First filial – F1 generation, offspring of P generation, hybrids – heterozygous Rr • Second filial – F2 offspring of hybrid cross, phenotype ratio 3:1

  13. J. Independent assortment • Dihybrid cross –TtGg x TtGg • predicted phenotypes 9:3:3:1 • T = tall • t = dwarf fill this in • G = green • g = albino

  14. Being black, sire and dam must both be B-E-; having produced yellow and chocolate pups, each must also have the b and e alleles, so in each case the genotype is BbEe. A BbEe parent can contribute the four combinations of alleles BE, bE, Be, and be to various pups.

  15. BBEE (1 pup in sixteen or 6.25%) blackBbEE (2/16 or 12.5%) blackBBEe (2/16 or 12.5%) blackBbEe (4/16 or 25%) blackbbEE (1/16 or 6.25%) chocolatebbEe (2/16 or 12.5%) chocolateBBee (1/16 or 6.25%) yellowBbee (2/16 or 12.5%) yellowbbee (1/16 or 6.25%) yellow with brown nose and light eyes

  16. II. Human genetics • A. Karyotyping – human chromosomes • Autosomal – 22 pairs of somatic • Sex chromosomes – 1 pair XX or XY

  17. Pedigree – genetic • relationship in families • http://www.zerobio.com/drag_gr11/pedigree/pedigree1.htm • Abnormalities – • different • from the norm • Disease – • serious disorders • or abnormalities • caused by genes

  18. III. Human genes • A. Autosomal recessive inheritance – must have both recessive alleles • Albinism – aa , can’t make melanin • Tay-sachs disease – at 6 months develops spot on retina  blindness, death • Cystic fibrosis – most common 1/2500 children • Lactose intolerance – don’t have lactase • Sickle cell anemia – red blood cells, sickle shaped – so can’t carry O2 well and get stuck in capillaries

  19. Autosomal dominant inheritance – two dominant alleles or heterozygous • Darwin tubercle – thickened rim of cartilage in ear • Achondroplasia – dwarfism • Huntington’s disease – manifests in 30’s or 40’s, loss of muscle control, loss of brain tissue • Polydactyly – 6 fingers or toes

  20. IV. Sex-linked human inheritance – traits carried on the x chromosome • Sex – linked disorders • XX normal female, • X-X female carrier, • X-X- afflicted female, • X-Y afflicted male, • XY normal male • Hemophilia – bleeding disorder X-Y or X-X- • 2. Colorblindness – red- green –blue , • X-Y or X-X-

  21. V. Incorrect chromosome number – any number but 46 in humans (Down syndrome- 47) trisomy on the 21st chromosome • Disjunction abnormalities – extra or too few, occurs in meiosis, can also result in some degree of mental retardation and increased risk of diseases and defects • 1. Turners syndrome: XO • 2. Klinefelter syndrome: XXY • 3. Meta or super female: XXX • 4. Jacob syndrome: XYY

  22. VI. Gene Regulation in Eukaryotes • Female cat cells inactivate one of two X chromosomes in every cell (producing a Barr body) • Different patches of skin cells in a cat inactivate different X chromosomes • Patches of fur growing from skin cells may differ in color if fur genes on X chromosomes differ

  23. VII. Structural abberrations • Deletions – part of chromosome is missing, cri-du-chat syndrome #5, leukemia #21 • Inversions –part of chromosome is reversed • Translocation – part of one chromosome breaks off and attaches to another chromosome • Duplications – chromosome replicates genetic material it already has • VIII.Genetic screening • Ethical issues • insurance

  24. Chapter 11 DNA: The Molecule of heredity

  25. Chemical nature of genes • Coding capacity – genes carry codes produces traits in the organism • Transformation – A T G C • Adenine Thymine Guanine Cytosine • nucleotide code for all traits • DNA – deoxyribonucleic acid • Base composition • Chargaff’s rule – • A – T, T – A, G – C, C - G • Double helix model – 1953 by Watson and Crick – nucleotides form rungs of ladder, phosphate and ribose (sides)

  26. Purines – 2 carbon ring, adenine and guanine • Pyrimidines – single carbon ring, thymine and cytosine • Base pairing – A  T, G  C • DNA replication • Template – bases need to form a complimentary strand • DNA polymerase – enzyme which separates the base pairs – separates the DNA molecules • Mutations • Alteration of the bases

  27. Chapter 12 Gene Expression and Regulation

  28. RNA – ribonucleic acid – one strand • Composition – CG, AU , cytosine, guanine, adenine, uracil • Function – carry DNA instructions to various cell parts • Protein synthesis – code for amino acid sequences

  29. Messenger RNA – mRNA, carries DNA instructions “codons” • E. Transfer RNA – tRNA, translate the code “anticodons” • F. Ribosomal RNA – rRNA, from code puts amino acids together to form proteins • G. RNAi- interference RNA- destroys “suspect” codes such as viruses

  30. RNA Intermediaries • There are three types of RNA involved in protein synthesis • Messenger RNA (mRNA) carries DNA gene information to the ribosome • Transfer RNA (tRNA) brings amino acids to the ribosome • Ribosomal RNA (rRNA) is part of the structure of ribosomes

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