1 / 15

Genetics of Inheritance

Genetics of Inheritance. History. Gregor Mendel was a monk who did experiments on garden peas in the 1860s. Peas have many varieties and strict control over mating is possible. Mendel. Example: Mendel bred round peas and wrinkled peas. The first generation had only round peas.

scott-rush
Download Presentation

Genetics of Inheritance

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 of Inheritance

  2. History Gregor Mendel was a monk who did experiments on garden peas in the 1860s. Peas have many varieties and strict control over mating is possible.

  3. Mendel Example: Mendel bred round peas and wrinkled peas. The first generation had only round peas. When the first generation round peas were self-fertilized, the second generation had one wrinkled pea plant for every three round pea plants…. Why???

  4. Mendel Each gene has 2 alleles (forms of the gene). An allele can be dominant (designated by a capital letter), or recessive (designated by a lower-case letter). The combination of alleles is called the genotype.

  5. Pea Genotypes Let R = dominant round pea allele Let r = recessive wrinkled pea allele Possible genotypes for pea plants: RR Rr rr Terms: RR = homozygous (ie. “the same”) dominant Rr = heterozygous (ie. “different”) rr = homozygous recessive

  6. Pea Phenotypes The expression of the genotype in the organism is called the phenotype. Resulting phenotypes: RR (round peas) Rr (round peas) Why? The dominant round allele masks the recessive wrinkled allele rr (wrinkled peas)

  7. A Closer Look… One parent had the genotype RR. What alleles can it donate to its haploid sex cells? Only the R allele The other parent had the genotype rr. What alleles can it donate? Only the r allele After fertilization, ALL offspring will therefore have the combination of R and r, resulting in Rr (round peas).

  8. A Closer Look… When these first generation (a.k.a F1 generation) peas are making gametes, which alleles could be present for each parent? R r

  9. R r Possible alleles for each gamete R r A Closer Look… What are the possible genotypes for the F2 generation? (draw a matrix chart… a.k.a a Punnett Square)

  10. R r R r A Closer Look… Fill in the possible genotypes in the square. RR Rr Rr rr

  11. R r R r The answer is… Genotypic Ratios: ¼ will be RR 2/4 or ½ will be Rr ¼ will be rr RR Rr Rr rr

  12. R r R r The answer is… Phenotypic Ratios: ¾ will be Round ¼ will be Wrinkled RR Rr Rr rr

  13. Terms: RR = homozygous (ie. “the same”) dominant Rr = heterozygous (ie. “different”) rr = homozygous recessive The mystery is solved!

  14. An example: Example: A heterozygous purple-flowered pea plant (Pp) is crossed with a homozygous recessive white-flowered pea plant (pp). a) What are the expected genotypic ratios? b) What are the expected phenotypic ratios? (hint: start with the possible alleles for the gametes, then make the Punnett Square)

  15. Dihybrid Crosses:

More Related