1. Bell Ringer 1.Fill in the table correctly. MitosisMeiosis Creates somatic cells Concerns sexual reproduction Forms haploid daughter cells Used for growth and repair Forms unique cells

2. Mendelian Genetics Can we predict what offspring will look like?

3. Mendelian Genetics We can determine an organism’s physical traits (characteristics) by examining its chromosomes. Chromosomes are made up of a series of genes, sequences that code for proteins. In the mid-1800s, Gregor Mendel experimented with pea plants. He discovered that he could predict what the offspring of pea plants would look like, as the parents were passing down their physical traits to their offspring. This lead to two vital laws: the laws of segregation and independent assortment.

4. Segregation The law of segregation states that every physical trait has a unique gene that codes for it. All of the different possibilities for each trait are called alleles. Example: alleles for eye color: black, brown, blue, etc. Since you have two of every chromosome, you have two alleles for ALL of your traits. Your alleles are split up when forming new gametes!

5. Independent Assortment The DNA in your cells is randomly separated in anaphase I. For each chromosome pair, there is a 50% chance of getting either chromosome. Independent assortment: the idea that each gamete randomly receives chromosomes in meiosis.

6. Independent Assortment

7. Alleles One pair of alleles will determine one specific physical trait. In traditional Mendelian genetics, all traits have two possible alleles: A dominant allele, which will ALWAYS dictate the physical trait if present A recessive allele, which ONLY dictates the physical trait if there are NO dominant alleles present

8. Alleles The exact pair of alleles is referred to as a genotype. Your physical trait is called a phenotype. Genotype – “genes” – genetic sequences Phenotype – “physical” – physical appearance Genotype ALWAYS controls phenotype!

9. Alleles Rules: Dominant alleles are typically given a capital letter. Recessive alleles receive a lowercase letter. Example: if yellow peas are dominant, and green peas recessive, then Y = yellow, and y = green. If the genotype contains ANY dominant alleles, the phenotype will be dominant. So, BOTH YY and Yy will produce YELLOW peas. You will ONLY see the recessive trait if you have TWO recessive alleles. In other words, the ONLY way to make green peas is with the genotype yy!

10. Alleles Rules: If you have two of the same alleles, you have a homozygous pair. “Homo-” means the same. If you have two different alleles, you have a heterozygous pair. “Hetero-” means different. Using our previous example of yellow and green peas: The genotype YY is homozygous dominant, and makes yellow peas. The genotype Yy is heterozygous, and makes yellow peas. The genotype yy is homozygous recessive, and makes green peas.

11. Punnett Square We can use a device called a Punnett square to predict what offspring will look like. A Punnett square is a grid that shows all possible offspring.

12. Punnett Square Monohybrid squares are very easy to use: 1.Take the genotype of one parent, and split the alleles. Place them on the top of the square. Example: YY crossed with yy.

13. Punnett Square Monohybrid squares are very easy to use: 2.Take the genotype of the other parent, and split the alleles. Place them to the left of the square. Example: YY crossed with yy. YY

14. Punnett Square Monohybrid squares are very easy to use: 3.Fill in your square by crossing the alleles together. Example: YY crossed with yy. YY y y

15. Punnett Square What genotypes will our offspring be? What phenotypes will our offspring be? YY yYy y

16. Common Monohybrid Crosses We will examine some of the most common monohybrid crosses you will see. Pay close attention to the genotypic and phenotypic outcomes! For our examples, P = purple flowers, p = white flowers.

17. Common Monohybrid Crosses Crossing a pure dominant with a pure recessive. Example: PP x pp Genotypic ratio: 100% Pp (hybrid) Phenotypic ratio: 100% purple flowers PP pPp p

18. Common Monohybrid Crosses Crossing two hybrids. Example: Pp x Pp Genotypic ratio: 1 PP: 2 Pp: 1 pp 25%/50%/25% Phenotypic ratio: 75% purple flowers: 25% white flowers 3:1 purple to white Pp PPPPp p pp

19. Common Monohybrid Crosses Crossing a hybrid with a pure recessive. Example: Pp x pp Genotypic ratio: 50% Pp: 50% pp 1 Pp: 1 pp Phenotypic ratio: 50% purple flowers: 50% white flowers 1:1 purple to white Pp pPppp pPppp

20. Dihybrid Crosses Say you want to cross a tall purple flower with a short white flower. You will be crossing two different traits. Can we find out what the offspring will look like?

21. Dihybrid Crosses According to Mendel’s law of independent assortment, the genes for two different traits will always be on different chromosomes. We CAN determine how two different traits can be passed down, though. This requires the use of a dihybrid cross.

22. Dihybrid Cross In a dihybrid cross, you will cross two traits at the same time. Since each gamete has to have one copy of each chromosome, you need to assign each side of the Punnett square TWO letters; one for each trait! http://www.youtube. com/watch?v=PdQPX VZqyT8 http://www.youtube. com/watch?v=PdQPX VZqyT8

23. Dihybrid Crosses All organisms in a dihybrid cross will have four alleles. You’ll need to separate them into gametes using the FOIL method! Example: Parent has the genotype AaBb. Front: AB Outside: Ab Inside: aB Last: ab

24. Dihybrid Crosses Then, place each gamete pair along the top of the Punnett square. ABAbaBab

25. Dihybrid Crosses Do the same for the other parent. Example: Parent has the genotype AaBb. Front: AB Outside: Ab Inside: aB Last: ab ABAbaBab

26. Dihybrid Crosses Now, fill in each cell of the dihybrid Punnett square. Always keep the same letters together. Also, keep the letters in the same order! ABAbaBab AB Ab aB ab

27. Dihybrid Crosses ABAbaBab ABAABBAABbAaBBAaBb AbAABbAAbbAaBbAabb aBAaBBAaBbaaBBaaBb abAaBbAabbaaBbaabb

28. Dihybrid Crosses From there, you can determine the genotypic and phenotypic ratios. Remember, genotypic ratios are the number of different sequences, and phenotypic ratios are the number of different appearances. When counting genotypes, ALWAYS work from most to least dominant.

29. Dihybrid Crosses SequenceNumber AABB1 AABb2 AAbb1 AaBB2 AaBb4 Aabb2 aaBB1 aaBb2 aabb1 ABAbaBab ABAABBAABbAaBBAaBb AbAABbAAbbAaBbAabb aBAaBBAaBbaaBBaaBb abAaBbAabbaaBbaabb

30. Dihybrid Crosses For this particular cross, the genotypic ratio is 1:2:1:2:4:2:1:2:1 Don’t worry – you won’t see any crosses this complex. You will have much simpler ones to do!