Genetics

1. Genetics Chapter 9 and 12

2. Gregor Mendel • 1842 • Studied heredity- the transmission of characteristics from parents to offspring. • Studied garden peas- Pisum sativum

3. Mendel's Work • Looked at peas’ traits • Height (tall or short) • flower position (axial or terminal) • pod appearance (inflated or constricted) • pod color (green or yellow) • seed texture (smooth or wrinkled) • Flower color (purple or white)

4. Mendel’s Methods • Pollination - from anther to stigma • Self-pollination • Cross-pollination

6. Types of Pollination

7. His experiments • Mated pure plants through self pollination. • Created strains of plants. • Created P1 or parent generations. • Crossed the plants to get F1 or first filial generations. AKA 1st offspring. • Then crossed F1 plants to create F2 Plants. AKA 2nd generation offspring.

8. Conclusions (pg 167-168) • Axial + terminal = axial • Green + yellow = green • Purple + white = purple • THEREFORE…. • Found factors – pairs for each trait. • 2 Alleles per trait (ex Gg)

9. Recessive vs Dominant Traits • Dominant = controlling or over powering allele. • Recessive= overpowered not controlling allele. Can be masked • Law of segregation= pair of factors is segregated, or separated, during the formation of gametes. • AKA one from dad, one from mom -> join to make a pair.

10. Chromosomes and Genes • Molecular genetics= study of structure and function of genes. • Alleles- one half of a pair of genes • ex. Aa, “A” is an allele. “a” is an allele. • Probability- the likelihood that a specific event or trait will occur. • ratios

11. Genotype and Phenotypes • Genotype= genetic makeup of an organism. (Gg) • Phenotype= Physical appearance of organism as a result of its genotype. (green) • Homozygous= both alleles are the same (GG) • Heterozygous= alleles are different (Gg)

12. Punnett Squares and Crosses • Monohybrid Crosses- cross for ONE pair on contrasting traits. • Homozygous Dominant (PP) x Homozygous Recessive (pp)

13. Homozygous (BB) x heterozygous (Bb) Heterozygous (Bb) x heterozygous (Bb) Monohybrid Cont.

14. Test Crosses • Unknown genotypes of parents • Known phenotypes of offspring BB=black, Bb= black, bb=brown • 2 black:2brown • One parent is brown (bb)

15. Incomplete Dominance • Two or more alleles influence the phenotype. AKA “mixing” • Neither allele is dominant • EX: RR=red, Rr=pink, rr=white • Geno=1RR:2Rr:1rr • Pheno=1red:2pink: • 1white

16. Co dominance Page 176 • Both alleles are expressed in heterozygous offspring. • Example- a horse has a gene for both red and white hair. Therefore he has strands of white hair and strands of red hair.

17. Dihybrid Crosses • Involves two pairs of contracting traits. • EX= seed texture and seed color • Homo Dom x Homo Recessive • R (round) is dominant over r (wrinkled) • Y (yellow) is dominant over y (green) • Cross rryy (homogenous wrinkled green) with RRYY (homogenous round, yellow)

18. RRYY X rryy (Homozygous dominant X recessive)

19. Heterozygous X Heterozygous RrYy X RrYy

20. Hetero X Hetero Results • Genotypic ratio • 1RRYY: 2RRYy: 2RrYY: 4 RrYy: 1RRyy: 2Rryy: 1rrYY: 2rrYy: 1rryy • Phenotypic Ratio • Always 9:3:3:1 (total 16) • 9 dominant for both traits • 1 recessive for both traits

21. Results Continued • 9/16 round and yellow • 3/16 round and green • 3/16 wrinkled and yellow • 1/16 wrinkled and green • **Remember** • 9:3:3:1

23. Sex determination of Offspring • Cross XX (mom) with XY (dad) • Geno Always = 2XX:2XY • Pheno Always= 2females:2males

24. Sex Linkage • Genes that are found only on the “X” chromosome or the “Y” chromosome. • color blindness (inherited from mom) • hemophilia • Ex Fly eye color (Morgan) • F1= all red eyes • F2= 3 red: 1white • White was ALWAYS male • THUS, eye color is carried on the “X” chromosome.

25. Results • F1- all red eye because they all carry “R” • F2- • 3 red eyed (carry “R” • 1 white (does not carry “R” )

27. X- Influenced • Traits influenced by sex hormones. • Phenotypes differ even is genotypes are the same. • Pattern baldness • B=bald • B’=non bald • Dominant in males, Recessive in females • **Females only show if both alleles are dominant. **

28. Blood Type • Controlled by multiple alleles • iA, iB, and i (iO). • A and B are co dominant. • A and B are dominant to O.

30. Pedigrees (see page 227) • Record of how a trait is inherited over several generation. • Determines carriers- organisms that have the gene but do not show the phenotypic trait. • Used to determine genetic disorders.

33. Additional Info • Chromosome Map- diagram that shows a linear sequence of genes on a chromosome. • Mutation- some sort of change in the gene sequence. Can be good or bad.

34. Chromosome Map

35. Trisomy 21

36. Great Apes Karyotype

37. Mutations Cont. • Chromosome Mutations • Deletion- loss of part of a chromosome. • Inversion- break off and reattach in reverse. • Translocation- break off and attaches to another chromosome.

38. Gene Mutations • Point Mutation- substitution, addition, or removal of a single nucleotide. • Ex sickle cell anemia (A for T) • Substitution- nucleotides switch • Frame Shift- caused by deletion or addition.

39. Ways to detect genetic Disorders. • Genetic Screening • Genetic Counseling • Amniocentesis • Chorionic villi sampling • Pedigrees

40. Genetic Traits and Disorders • Huntington’s Disease- (single allele) • Blood Type- (multiple alleles) • Skin Color- (polygenic alleles) • Non-disjunction (addition or subtraction of chromosomes) • Monosomy- One chromosome • Trisomy- Three chromosomes • Trisomy-21 – Down Syndrome

41. Huntington’s Disease