“FATHER OF GENETICS” • Genetics- • scientific study of heredity; how traits are inherited Gregor Mendel • Heredity • the passing of traits • from parents to offspring
Pea plants have many traits • (tall/short, purple flowers/white flowers) • self-fertilizedor cross-fertilized Mendel’s Pea Plant ExperimentsWhy Peas?
True-Breeding Plants: • create plants that look like themselves • HybridPlants: • offspring of true-breeding plants • Tall x Short = Hybrid
Drill: April 2, 2012 • What is a gene? An allele? • Define and differentiate between a true/pure-breed and a cross-breed/hybrid? • Self-pollination vs cross-pollination: Explain each and how did Mendel prevent self-pollination.
-One trait dominates & “hides” the other Tall x Short = all tall offspring (hybrids) *Tall is the dominant trait * Short is recessive Dominance
Mendel discovered that each trait is controlled by two factors • Genes – factors that determine your traits • Alleles-different forms of a gene Genes and Alleles
Mendel’s Experiments Draw the crosses
When a parent makes sperm or eggs, their genes separate (PRINCIPLE OF SEGREGATION) Gametes contain either a T allele (tall) or a t allele (short) Explaining the Cross
GENOTYPE - what genes the organism has (TT, Tt, tt) PHENOTYPE - what the organism looks like (tall or short)
Check for understanding 1. A one-eyed purple people eater is crossed with a two eyed purple people eater. All of their offspring have two eyes. Which trait is dominant? 2. If you use the letter E for this gene. What is the genotype of the offspring? Are these offspring the F1 or F2 generation? 4. If you crossed the offspring with each other? How many of the new offspring would you expect to have two eyes?
More checking 5. The passing of traits from parents to offspring is known as _________________ 6. Who was the father of genetics? _________ 7. A single gene will code for a ______________, such as flower color. 8. Every gene is made of two ______________
Drill: Thursday 5, 2011 1) How did Mendel find out whether the recessive alleles were still present in the F1 plants? 2) About one fourth of the F2 plants from Mendel’s F1 crosses showed the trait controlled ______ by the allele. 3) The dominant allele is represented by and a recessive allele is represented by .
Probability: the likelihood that a particular event will occur is called_______. The probability that a single coin flip will come up heads. • a. 100 percent • b. 75 percent • c. 50 percent • d. 25 percent
Probability TRUE or FALSE The past outcomes of coin flips greatly affect the outcomes of future coin flips Q: Why can the principles of probability be used to predict the outcomes of genetic crosses? A: The way in which the alleles segregate is completely random, like a coin flip
PunnettSquare can be used to predict and compare the genetic variations that will result from a cross. Show possible genotypes for the F2 offspring.
Practice #1: In seals, the gene for the length of the whiskers has two alleles. The dominant allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers. a) What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered seals, one that is homozygous dominant and one that is heterozygous? b) If one parent seal is pure long-whiskered and the other is short-whiskered, what percent of offspring would have short whiskers?
Practice #2: A green-leafed luboplant (I made this plant up) is crossed with a luboplant with yellow-striped leaves. The cross produces 185 green-leafed luboplants. Summarize the genotypes & phenotypes of the offspring that would be produced by crossing two of the green-leafed luboplants obtained from the initial parent plants.
Allele Types Definitions • Organisms that have two identical alleles • particular trait (TT or tt) Homozygous • Organisms that have two different alleles • same trait (Tt) Heterozygous • Physical characteristic of an organism Phenotype • Genetic makeup of an organism (Tt) Genotype
Independent Assortment • In a 2-factor cross, Mendel followed 2 genes passed from one generation to the next • Phenotype Genotype (true-bred) a. round yellow peas __RRYY_ b. wrinkled green peas __rryy_
Independent Assortment RRYY rryy F1 generation = heterozygous dominant with round yellow peas RrYy
Independent Assortment • Circle the letter of the phenotypes that Mendel would expect to see if genes segregated independently. • a. round and yellow • b. wrinkled and green • c. round and green • d. wrinkled and yellow
Overall concept: Q: What did Mendel observe in the F2 offspring that showed him that the alleles for seed shape segregate independently of those for seed color? A: He observed F2 offspring that had combinations of phenotypes—and therefore combinations of alleles—not found in either parent.
2-Factors:Sample Problem • Dihybrid Cross
Dihybrid Cross Problem #1: In the breeding season, male Anole lizards court females by bobbing their heads up and down while displaying a colorful throat patch. Assume for this question that both males and females bob their heads and have throat patches. Assume also, that both traits are controlled by single locus genes on separate chromosomes. Now, suppose that anoles prefer to mate with lizards who bob their heads fast (F) and have red throat patches (R) and that these two alleles are dominant to their counterparts, slow bobbing and yellow throats. A male lizard heterozygous for head bobbing and homozygous dominant for the red throat patch mates with a female that is also heterozygous for head bobbing but is homozygous recessive for yellow throat patches
a) How many of the F1 offspring have the preferred fast bobbing / red throat phenotype (assume 16 young)? b) What percentage of the offspring will lack mates because they have both slow head bobbing and yellow throats? What percentage of the offspring will have trouble finding mates because because they lack one of the dominant traits? a) 12 b) 0% c) 25%