Genetics

1. Genetics The study of inherited traits +

2. Jennifer and Homer Simpson If the two of them were to get married, would their children look like this?

3. Definitions • Heredity – the passing of traits from parents to offspring • GregorMendel – the father of genetics • Self-pollination – all traits are received from the one parent • Cross-pollination – seeds are produced as offspring from two different plants • Purebred – offspring are bred for specific traits by mating identical parents

4. Traits – an organism’s characteristics passed on by the biological parents • Hybrids – offspring created by crossing parents with different characteristics • Genes – segments of DNA that code for traits • Alleles – letters that are used to express the frequency of traits • Dominance – individual traits that are more likely to be expressed in a population, capital letters

5. Recessive – traits less likely to be visible in a population , lower case letter. • Segregation– separation of alleles during meiosis • PunnettSquare – a probability chart used to determine possible outcomes for the inheritance of traits • Phenotype – a description of an organism’s physical appearance, what it looks like. • Genotype – a two letter code using alleles that expresses the dominance of an individual, what genes/letter are there.

6. Probability – the % chance of a specific trait or set of traits being inherited • Homozygous – the two alleles that represent a trait are exactly the same, ex. HH, hh • Heterozygous – the two alleles that represent a trait are different, ex. Hh • One-Factor Cross – only one allele is used in a Punnett Square, ex. Hair color • Two-Factor Cross – two sets of alleles are used to determine probability of having two linked traits, ex. Hair and eye color

7. What is Genetics? • Genetics is the study of traits and how they are chemically passed from one generation to their offspring by meiosis and fertilization

8. Where did Genetics get its Start? • Gregor Mendel (a Biology Teacher and a Catholic Priest) made some observationswhile working in the monastery gardens • He hypothesized that each organism had its own unique set of traits that could be transferred from one organism to the next. • He used pea plants to test and support his hypothesis. First:  peas exhibit a number of contrasting traits that Mendel could easily studySecond: pea plants can easily be cross pollinatedThird:a relatively large number of seeds are produced

9. The Start of Genetics cont. • Mendel's first observations showed that peas self pollinate. • Each pea plant had its own egg and sperm. • He exchanged male and female pollen from two different plants to force cross-pollination. (hybrid) • The plants that weren’t switched were purebreds.

10. Gregor Mendel1822 - 1884

11. Genes and Dominance Dominant • Every organism has certain characteristics called traits. • Each trait is expressed by a two letter code (alleles) • Some alleles are stronger than others (dominant) and others are weaker (recessive) Recessive T=Tall t=short

12. Each trait is expressed by a _________? What are stronger traits called? What are weaker traits called? Two letter code (alleles) Dominant Recessive Number your paper from 1 to 3Do Not skip a space!

13. Alleles • Each trait is controlled by two genes (1 from each biological parent) • Genes can be represented by letters • An uppercase letter denotes the wild type (usual, dominant) form of the gene • A lowercase letter denotes the mutant (unusual, recessive) form of the gene • There are three distinct combinations; e.g. TT,Tt, and tt • If a dominant gene is paired with a recessive gene, the dominant's trait will usually out power the recessive, but not always

14. How many genes control one trait? What are genes represented by? If a dominant and recessive gene are paired together, which trait is seen? Two Letters Dominant Questions 4, 5, & 6

15. Punnett Squares • To set up a Punnett square, draw a large square, and then divide it into 4 equal sections. It should look something like this:

16. Punnett Squares cont. Now you need two parents to mate with a known genotype. For example, a red flower (genotype Rr) and a white flower (genotype rr). Place one of the parents on top, and one on the left. You should get a something similar to this: R r r r

17. Punnett Squares cont… • Take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this: R r r Rr rr r Rr rr

18. Each punnett square is equal to 100% of the possible genotypes. Therefore each box in our punnett square is equal to 25% probability We can then look at the results of our Punnett Square and determine the probability of traits. 50% of the squares are Rr; 50% are rr We can assume there is a 50% chance the flowers will be red or 50% chance of them being white. Punnett Squares cont….

19. What is each punnett square worth in percentage? If there are 10 boxes in a Punnett Square, what would each individual box represent in percentage? 100% 10% Questions 7 & 8

20. Find out the probability of having a tall or short plant using these two genotypes. TT and tt (T = Tall t = short) Try your own Punnett Square

21. Genotype is the genetic code (alleles) for an organism. Phenotype is the actual physical appearance. Genotype and Phenotype Phenotype Genotype • Blonde Hair = BB • Green Hair = bb • Brown eyes = AA • Yellow eyes = aa

22. Figure out probability of this problem.Write down each of their traits for hair and eye color +

23. The Grinch Phenotype: Green Hair Yellow Eyes Genotype: bb (green hair) aa (yellow eyes) Britney Spears Phenotype: Blonde Hair Brown Eyes Genotype: BB (blonde hair) AA (brown eyes) The Information Make your Punnett Squares

24. Try again! + This time, come up with your own set of alleles for hair color and skin color.

25. Is this what their kids would look like?