1 / 28

Genetics: A Monk a Pea and a Fly

Genetics: A Monk a Pea and a Fly. Mendel and His Peas. Born in Czech Republic in 1822 Studied math in Vienna Was in charge of the monastery garden Conducted controlled breeding between true-breeding pea plants to study inheritance. Garden Peas : Tasty and Educational. Easy to grow

orpah
Download Presentation

Genetics: A Monk a Pea and a Fly

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. Genetics: A Monk a Pea and a Fly

  2. Mendel and His Peas • Born in Czech Republic in 1822 • Studied math in Vienna • Was in charge of the monastery garden • Conducted controlled breeding between true-breeding pea plants to study inheritance

  3. Garden Peas : Tasty and Educational • Easy to grow • Fast growing • Number of easily recognized traits • Lots of offspring (each seed) • Easy to control crossing

  4. Mendel’s Crosses

  5. Dominant and Recessive Traits • Noticed traits in the F1 were not a blend of the parents but, instead favored one parent • Trait that shows up the F1 generation is Dominant the trait that is masked is Recessive • Today : Traits chemical factors = Genes Forms of a trait = Alleles

  6. The F1 Cross • Mendel then crossed the F1 plants and the recessive trait reappeared! • What happened? *Segregation : Alleles on homologous chromosomes separate when sex cells are produced Think about the logic here

  7. Genotypes and Phenotypes • Genotype : expression of alleles present Dominant alleles : Capital first letter of the dominant trait Recessive alleles : Lower case script of the first letter of the dominant trait Homozygote : Two of the same allele Heterozygote : Two different alleles • Phenotype : Actual visible trait

  8. Example : Flower color Purple (P) is dominant to white (p) Cross a pure breeding plant with purple flowers with a pure breeding plant with white flowers. 1) Determine genotypes 2) Segregate alleles 3) Perform cross

  9. Probability and Genetics • Chance of an event occurring : probability • Does not indicate something will happen only the likelihood that it can happen • Allele combinations follow rules of probability • Probabilities in genetics can be determined using simple math or Punnett squares

  10. Mr. Curry’s Never Miss, Easy, Solves Every Type of Genetics Problem Method • Define alleles • Define phenotypes associated with genotypes • Write out cross • Produce gametes • Perform cross (Punnett square) • Determine genotypic and phenotypic ratios of offspring • Answer the problem

  11. 0

  12. Typical Monohybrid • Homozygous Dominant X Homozygous Recessive P= F1= F2=

  13. Two Traits at Once : Dihybrid Cross • How do you determine inheritance for two traits at once? - Dihybrid Cross • Just remember : Segregation and Independent Assortment (For now, these genes exist on separate chromosomes)

  14. In the fruit fly Drosophilamelanogaster, vestigial wings and hairy body are produced by two recessive alleles carried on different chromosomes. The normal alleles, long wings and hairless body, are dominant. If a vestigial-winged, hairy male is crossed with a female homozygous for • both of the normal traits, what would be the phenotypes and genotypes of their progeny? If the • F1 generation was allowed to mate randomly among themselves, what phenotypes and genotypes would be expected among the F2’s, and in what proportions?

  15. In some breeds of dogs, a dominant allele controls the characteristic of barking while trailing. In • these dogs, another, independent gene controls ear shape, erect ears being dominant over floppy ears. • If a dog breeder wants to produce a true-breeding strain of floppy-eared dogs that bark on the trail, • how should she proceed, knowing that the alleles for erect ears and silent trailing are present in her • kennels?

  16. P cross = Homozygous Dominant X Homozygous Recessive P= F1= F2=

  17. Other Types of Inheritance • Not all genes are dominant or recessive • Sometimes get both alleles, a modified form or the dominant or something new altogether

  18. Incomplete Dominance • Two alleles produce three phenotypes • Third phenotype is a muted version of the “dominant” • Example 4 O’clock flowers RR = Red RW= Pink WW = White

  19. Codominance • When two alleles are both equally expressed in the heterozygote • Example : ABO bloodtypes IAIA, IAi =A type blood IBIB, IBi = B type blood IAIB = AB type blood ii = O type blood

  20. Sex Determination • In all animals : Sex is determined by the combination of sex chromosomes (23rd pair in humans) • XX = female • Xy = male

  21. Polygenic Inheritance • Traits are governed by more than one gene • Most traits are polygenic • Each gene may have two or more alleles • Many genes can be codominant or incompletely dominant • Heterozygotes are intermediate in phenotype

  22. A recessive gene combination will effect the phenotype

  23. Multiple Alleles

  24. The Fruit Fly Drosophila melanogaster Homo sapiens

More Related