1 / 34

Fundamentals of Genetics Chapter 9

Fundamentals of Genetics Chapter 9. What makes you who you are, your genes or your environment????? BOTH!!!. Thalidomide (1957-1961)  -causes phocomelia (flipperlike arms/legs) Can you think of other examples?. Environmental Influences. Mendel.

boydn
Download Presentation

Fundamentals of Genetics Chapter 9

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fundamentals of GeneticsChapter 9 • What makes you who you are, your genes or your environment????? • BOTH!!! .

  2. Thalidomide (1957-1961)  -causes phocomelia (flipperlike arms/legs) Can you think of other examples? Environmental Influences

  3. Mendel • Gregor Mendel (Born 1822) Monk worked with pea plants

  4. Stamens:  actually anthers on the end of the stamen produces pollen which contains sperm cells inside (male structure) Stigmas:  actually ovary in pistil produces egg cells (female structure)

  5. What Mendel did with Pea Plants • Removed stamens from flowers so self-pollination could not occur. • Worked with only one visible trait at a time. • Kept detailed record of crosses and results.

  6. Terminology for Results • Parent generation P1 •  Offspring of parent generation =F1 (first filial generation) •  Offspring of offspring=F2 (second filial generation)

  7. Page 176 in book What do you notice about the observed ratio?

  8. Mendel's Experiment - P1=tall x short - F1=all tall - F2= 3/4 tall and 1/4 short -Mendel studied many different traits Mendel’s Results

  9. This led Mendel to these conclusions: • Mendel's first hypothesis:  inherited characteristics are controlled by factors (genes) which occur in pairs. ex. Tt or TT or tt

  10. 2. Mendel's second hypothesis (Principle of dominance and recessiveness):  one gene of a pair may mask (hide) the other, or prevent it from having an effect.    • Ex. Tt= TALL  

  11. Mendel's third hypothesis:  (Law of Segregation):  a pair of genes are separated during the formation of the gametes (sperm and egg). 

  12. Law of Independent Assortment:  the separation of gene pairs occurs entirely independent of the separation of all other gene pairs in an organism.

  13. Molecular Genetics Supports Mendel • Gene- segments of DNA on a chromosome *genes occur in pairs • Genes have different forms called alleles *we use letters to represent alleles ex. T or t

  14. 5 Steps to a Punnett Square

  15. Genetic Problem • In eyecolor, BROWN is dominant to blue. Pres. George Bush is heterozygous for BROWN eyes. Laura Bush has blue eyes. Complete a Punnett square showing the possible eyecolors of their twin daughters.

  16. STEP #1 Write Genotypes of Parents • Males 1st, female 2nd • If Dominant use all Capital Letters • If Recessive use lower Case 1. GT: Bb x bb

  17. STEP #2- Write Phenotypes of Parents • Write Male 1st, female second • 1.GT: Bb x bb • 2. PT: BROWN x blue

  18. STEP #3 - Punnett Square • Draw Tic Tac Toe Board • Males on vertical side • Females on horizontal • Complete Punnett Square 1. GT: Bb x bb • PT: BROWN x blue 3.

  19. Step #4- Write Genotypic Ratio or Genotypic Fraction • Compares the chances of getting different genotypes in the offspring. 1. GT: Bb x bb • PT: BROWN x blue 4. GF: 2/4 Bb, 2/4 bb

  20. STEP #5- Write Phenotypic ratio or Phenotypic Fraction • Compare the chances of different phenotypes in the offspring. • 1. GT: Bb x bb • 2. PT: BROWN x blue 3. • 4. GF: 2/4 Bb, 2/4 bb • 5. PF: 2/4 BROWN, 2/4 blue

  21. In eyecolor BROWN eyes are dominant to blue eyes. Chuck is homozygous for BROWN, his wife Lyn has blue eyes. What color eyes can their kids have? • 1. BB x bb • 2. BROWN x blue • 3. • 4. GF: 4/4 Bb • 5. PF: 4/4 BROWN

  22. Special Punnett Squares 1. Test Cross • A punnet sq. done to determine if parent is homo or heterozygous. • Involves crossing the unknown parent genotype with a homozygous recessive genotype • BB or Bb x bb • If all offspring are dominant then parent was homozygous; if some offspring are recessive then parent was heterozygous.

  23. Test Cross Question • A purple flowered pea plant is crossed with a white flowered pea plant. 5 of the 6 pea plants resulting from the cross are purple but one is white. • What is the genotype of the purple pea plant?

  24. Occurs when the heterozygous is an intermediate between the homozygous dominant and recessive. Incomplete Dominance

  25. 2. Codominance • Occurs when both alleles are fully expressed in the offspring. • Neither allele is dominant, and no blending occurs.

  26. Blood Type • Ex of codominance • Blood types M, N, MN are determined by 2 alleles LM, LN

  27. Polygenic Traits • Most human characteristics are polygenic • Polygenic traits are controlled by several genes • Ex skin color, height, hair color • AABBCCDD- dark skin • AABBccdd or AaBbCcDd or…-med skin • Aabbccdd –fair skin

  28. Dihybrid Cross

More Related