1 / 15

Chap 9 : Fundamentals of Genetics

Chap 9 : Fundamentals of Genetics. Mendel -- Gregor Mendel – “Father of Genetics” – worked with pea plants. Discovered inheritance (passing of traits from parents to offspring). A. Terminology. 1. Pure or Strain – trait that’s always passed to offspring.

howe
Download Presentation

Chap 9 : Fundamentals of Genetics

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. Chap 9 : Fundamentalsof Genetics Mendel -- Gregor Mendel – “Father of Genetics” – worked with pea plants. Discovered inheritance (passing of traits from parents to offspring)

  2. A. Terminology • 1. Pure or Strain – trait that’s always passed to offspring. • 2. P1 generation – parents • 3. F1 generation – 1st filial generation – offspring of P1 • 4. F2 generation – offspring of F1

  3. B. 3 Principles of inheritance • 1. Principle of Dominance andRecessiveness – says that traits that mask other traits are called dominant traits (R) and those that don’t are recessive traits (r). • 2. Principle of Segregation – each trait is expressed by 2 factors – one from each parent • Ex. RR x rr = Rr • (mom) (dad) (offspring)

  4. 3. Principle of Independent Assortment – says traits are independent from each other.Ex. Eye color and hair color are independent of each other. C. Chromosomes and Genes gene – piece of DNA calling for a specific trait – like eye color allele – that form of a gene. Ex. Blue, brown, or green gene chromosome

  5. II. Genetic Crosses • A.1. Genotype – genetic makeup of an organism. Expressed with letters. (Rr) • 2. Phenotype – physical appearance of an organism (ex. Blue eyes) • 3. Homozygous – when both alleles of a pair are the same. (RR or rr) • 4. Heterozygous – when the alleles of a pair are not the same. (Rr)

  6. Ex. B- black b - blonde Bb (dad) x bb (mom) Geneotype: Bb bb Phenotype: black blonde heterozygous homo. Rec. Homozygous dominant – BB Homozygous recessive – bb 5. Multiple alleles – when 3 or more alleles control 1 trait. ex. Blood type : A, B, O

  7. 6. Probability – the likelihood of something occurring. #of 1 kind of event / # of events • Ex. 50 tosses of coin • 18 heads, 32 tails. What is the probability of tossing a head ? • 18/50 = 36 % B. Monohybrid crosses – cross between 1 trait

  8. --- Punnett Square – tool used to predict the probability from genetic crosses. • Types of Monohybrid Crosses • In rats brown fur is dominant over white fur. If a homozygous dominant and homozygous recessive parent produced offspring, what would be their genotypes and phenotypes ? B- brown b-white BB x bb G: 100% Bb b b P : 100% Brown B Bb Bb B Bb Bb

  9. 2. If two of the offspring from #1 were mated what would be the outcome ? B- brown b- white Bb x Bb G : 1 BB B b 2 Bb B BB Bb 1 bb b Bb bb P : 3 brown 1 white

  10. 3. In pea seeds round is dominant over wrinkled. If a heterozygous seed is mated with a wrinkled one what percentage would end up wrinkled ? R- round r – wrinkled Rr x rr r r R Rr Rr r rr rr 50 % would be wrinkled

  11. 4. Test Cross – used to determine the genotype of a dominant phenotype. • In mice red eyes are recessive to blue. A mouse has blue eyes and you want to know if red eyes “run in the family line”, how can you determine this ? --- Perform a test cross – cross the mouse with a homozygous recessive (one with red eyes). B? X bb = ?. If any offspring have red eyes you would know the allele in question was for red eyes.

  12. 4. Codominance – when one or more alleles is considered dominant. The result produces a blend of the alleles. • Ex. Flower petals exhibit codominance.If a red flower was crossed with a white flower describe the genotype and phenotype of the offspring. R – red R’ – white RR x R’R’ R’ R’ R RR’ RR’ R RR’ RR’ G: all RR’ P : all pink

  13. C. Dihybrid Crosses – cross between individuals that involves 2 different traits. • In Peas, round seeds are dominant to wrinkled and yellow is dominant to green. What would be the genotype and phenotye of the offspring of a homo.rec. and homo.dom. parents ? R – round G- yellow r – wrinkled g – green RRGG x rrgg 1 2 3 4 1 2 3 4

  14. RG(1+3) RG(1+4) RG(2+3) RG(2+4) (1+3) rg RrGg RrGg RrGg RrGg (1+4) rg RrGg (2+3) rg (2+4) rg G : all RrGg P : all round and yellow

  15. Ex. If two offspring from above were to be mated what would be the phenotypes of the offspring ? • RrGg x RrGg • RG(1+3) Rg(1+4) rG(2+3) rg(2+4) • RG RRGG RRGg RrGG RrGg • Rg RRGg RRgg RrGg Rrgg • rG RrGG RrGg rrGG rrGg • rg RrGg Rrgg rrGg rrgg • Phenotypes : • 9 round and yellow (R_G_) • 3 round and green (R_gg) • 3 wrinkled and yellow (rrG_) • 1 wrinkled and green (rrgg)

More Related