1 / 21

Understanding Mendel's Laws of Heredity

Explore Mendel's success in genetics, from careful subject selection to his groundbreaking experiments on pea plants. Uncover Mendel's monohybrid and dihybrid crosses, as well as the laws of dominance, segregation, and independent assortment.

rlabelle
Download Presentation

Understanding Mendel's Laws of Heredity

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. Mendels Laws of Heredity 10.1Martin aka Tha’ Boss

  2. WHY MENDEL SUCCEEDED? • Heredity: the passing on of characteristics from parents to offspring • Traits: the characteristics that are inherited • Genetics: the branch of biology that studies heredity

  3. WHY MENDEL SUCCEEDED? • A. Mendel Chose his subject carefully • He chose to use garden peas to experiment with • Because they reproduce asexually and have both male and female reproductive organs • Gametes: male and female sex cells • Fertilization: the union of male and female gametes to form a zygote • Zygote develops into a “seed”

  4. WHY MENDEL SUCCEEDED? • A. Mendel Chose his subject carefully • Pollination: when plants transfer pollen grains from the male reproductive organ to the female reproductive organ • Self-pollination: plants usually do this because they have both male and female organs • Let’s take a look at what Mendel did…

  5. WHY MENDEL SUCCEEDED? • Mendel cut away male pollen organs from purple • Mendel got pollen from the white plant and transferred it to the female part of the purple plant • Allowed purple plant to produce “seeds” from this pollination and planted seeds to see what color offspring would be produced.

  6. MENDELS MONOHYBRID CROSS • Hybrid: the offspring of parents that have different forms of a trait • Monohybrid: where two parents only differ by “one” trait

  7. MENDELS MONOHYBRID CROSS • A. The First Generation • Cross Pollination of 2 plants • 1 short, 1 tall • All offspring grew as tall as the tallest parent • The short plant characteristic has been “masked” in this generation • Parent 1 x Parent 2 = F1 Generation

  8. MENDELS MONOHYBRID CROSS • B. The Second Generation • Mendel allowed the F1 offspring to “self pollinate”, then planted the seeds • He noticed now that: • 3/4ths of the plants were tall • 1/4th of the plants were short • 3:1 ratio in the F2 offspring • F1 x F1 = F2

  9. MENDELS MONOHYBRID CROSS • C. The Rule of Unit Factors • Alleles: the different forms that genes can exist in • in other words, each gene is represented by two “letters”. Letters can be capital or lowercase. Each letter is an allele and each gene is represented by 2 letters/alleles • TT, Tt, tt

  10. MENDELS MONOHYBRID CROSS • D. The Rule of Dominance • Dominant: the observed trait in the F1 • Recessive: the trait that disappears in F1, only to return in the F2

  11. MENDELS MONOHYBRID CROSS • E. The Law of Segregation • States that every individual has two alleles of each gene and when gametes are produced, each gamete receives one of these alleles • During fertilization, gametes randomly pair to produce combinations of alleles

  12. MENDELS MONOHYBRID CROSS

  13. PHENOTYPES AND GENOTYPES • Phenotype: the way an organism looks or behaves • Its physical appearance • Tall, or short • Genotype: the allele combination an organism contains • TT, Tt, tt

  14. PHENOTYPES AND GENOTYPES • Genotypes can be described two ways • Homozygous: TT, or tt • Because the alleles are the “same” (homo) • TT is “homozygous dominant” • tt is “homozygous recessive” • Heterozygous: Tt • Because the alleles are different (hetero)

  15. MENDELS DIHYBRID CROSS • A. The First Generation: • Mendel took true breeding round yellow (RRYY) seeds and crossed with true breeding green/wrinkled (rryy) seeds • This produced an F1 that had all round/yellow seeds • This proved that yellow/round were the dominant traits

  16. MENDELS DIHYBRID CROSS • B. The Second Generation: • Mendel allowed a single F1 offspring to self-pollinate • This produced an F2 that had the following phenotypes • 9 – Round/Yellow • 3 – Round/Green • 3 – Wrinkled/Yellow • 1 – Wrinkled Green

  17. MENDELS DIHYBRID CROSS • B. The Second Generation: • The results from Mendel’s F2 experiment led him to his 2nd law regarding genetics • The Law of Independent Assortment

  18. MENDELS DIHYBRID CROSS • C. The Law of Independent Assortment: • States that genes for different traits are inherited independently of each other

  19. PUNNETT SQUARES AND PROBABILITY • We should all be able to complete monohybrid and dihybrid crosses using Punnett Squares at this time • We should be able to describe genotypes and phenotypes of offspring • We should be able to describe ratios among offspring and describe probabilities of phenotypes among offspring • But can we?

More Related