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Presentation on theme: "GENETICS."— Presentation transcript:


2 from parents to offspring
Gregor Mendel “FATHER OF GENETICS” Genetics- scientific study of heredity; how traits are inherited Heredity the passing of traits from parents to offspring

3 Mendel’s Pea Plant Experiments Why Peas?
Pea plants have many traits (tall/short, purple flowers/white flowers) self-fertilized or cross-fertilized

4 Tall x Short = Hybrid True-Breeding Plants: Hybrid Plants:
create plants that look like themselves Hybrid Plants: offspring of true-breeding plants Tall x Short = Hybrid

5 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.

6 Tall x Short = all tall offspring (hybrids)
Dominance -One trait dominates & “hides” the other Tall x Short = all tall offspring (hybrids) *Tall is the dominant trait * Short is recessive

7 Genes and Alleles Mendel discovered that each trait is controlled by two factors Genes – factors that determine your traits Alleles-different forms of a gene

8 Mendel’s Experiments Draw the crosses


10 Explaining the Cross 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)


12 Let's review what you know about genetics......

13 what the organism looks like (tall or short)
GENOTYPE  -  what genes the organism has (TT, Tt, tt) PHENOTYPE   - what the organism looks like (tall or short)

14 Are these offspring the F1 or F2 generation?
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?

15 6. Who was the father of genetics? _________
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 ______________

16 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 .

17 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

18 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

19 Show possible genotypes for the F2 offspring.
Punnett Square can be used to predict and compare the genetic variations that will result from a cross. Show possible genotypes for the F2 offspring.

20 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?


22 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.


24 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

25 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_

26 Independent Assortment
RRYY rryy RrYy F1 generation = heterozygous dominant with round yellow peas

27 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

28 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.

29 2-Factors:Sample Problem
Dihybrid Cross

30 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


32 What percentage of the offspring will have
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%

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