Wake Up Work #3

1. Wake Up Work #3 • What are homologous chromosomes? • What process starts with a diploid cell and ends with haploid cells? • What process creates new body cells? • If a mango has diploid cells with 40 chromosomes, how many chromosomes would it’s sex cells contain?

2. Genetics • Heredity – The passing of characteristics from parents to offspring • Traits – distinguishing characteristics that are inherited • Eye color, leaf shape, tail length, etc. • Genetics – the study of biological inheritance patterns and variations in organisms.

3. What are Genes? • A piece of DNA that provides set instructions to a cell to make a certain protein • Since a gene is a piece of a chromosome, and we have two of every chromosome, we have two copies of every gene to make every protein in our body!

4. What is an Allele? • Alleles are different versions of the same gene. • We have half of our chromosomes from each of our parents, but we may not have inherited the same version of every gene. • For example: We inherit genes that code for eye color, but we may inherit the specific directions to make brown eyes from mom and blue eyes from dad—those different types of genes are called alleles. • All cells have two alleles for each gene that may occur at a specific location • Each parent gives one allele

5. Homologous Chromosomes • Matching chromosomes from our mom (maternal) and dad (paternal). • They contain the same genes in the same locations, but may contain different alleles.

6. How do we Represent Alleles? • We use an uppercase or lowercase letter to represent one allele • UPPERCASE letters for DOMINANT • lowercase letters for recessive • We put two letters together to show what trait can be shown (remember…one from mom and one from dad) • Example: The dominant allele for height in pea plants is T, for tall and the recessive is t, for short

7. Are the Alleles the Same or Different? • If they are the same two of the same alleles at a specific location: HOMOZYGOUS • If they are different two different alleles at a specific location: HETEROZYGOUS

8. Dominant and Recessive Alleles • Dominant: This allele shows dominance over the recessive…if it is present, then the trait shows (Tt, or TT for a tall plant) • Recessive: For the recessive trait to show, both recessive alleles must be present (tt, for a short plant)

9. Genotype vs. Phenotype • Genotype • Combination of alleles (BB, Bb, bb) • Genetic makeup of a specific set of genes, • Phenotype • Physical characteristics/traits that are shown (blonde hair, blue eyes, attached earlobes)

10. Homozygous Dominant: BB Homozygous Recessive: bb Heterozygous: Bb

11. Face Drawing Lab • Pre Lab Questions • Read Intro on packet • Toss coin to choose male or female • Heads up is female • Tails up is male • Toss coin to determine each trait • Heads determines dominant • Tails determines recessive • Check on the table for each trait whether it is dominant, hybrid, or recessive for each trait

12. Agenda for 3/31/14 • Wake Up Work #1 • Finish Face Drawing Activity • Punnett Squares

13. Mendelian Genetics • Gregor Mendel was an Austrian monk who is known as the “Father of Genetics” because of his studies of how traits are passed in pea plants. • He described how traits were passed between generations • He did studies on pea plants in the 1860’s

14. Mendel’s Experiments • Mendel studied and bred pea plants. 3 reasons he chose to use the pea plant: • Had control over breeding: • Mendel used pea plants that typically self-pollinate • Used only purebred plants: • Purebred –creates offspring that have the same characteristics as the parent

15. He could observe“either-or” traits: • Chose pea shape, pea color, pod shape, pod color, plant height, flower color

16. Mendel Learned: • Organisms that reproduce sexually pass on only half of their genetic material to the next generation. • All traits are passed on. • Every individual gets one allele for each trait from each parent.

17. Mendel’s Laws • Mendel took meticulous notes on his investigations, and used them to develop three Laws of Inheritance. • The Law of Dominance • The Law of Segregation • The Law of Independent Assortment

18. Law #1Law of Dominance • States that some alleles are dominant while others are recessive • RR or Rr -Dominant allele present, the dominant trait is seen • rr -No dominant allele present, the recessive trait is shown

19. Law #2Law Of Segregation • Describes how chromosomes are separated during meiosis • During fertilization, gametes from different individuals randomly pair up to produce different combinations of alleles. (One from each parent) • So if a man has alleles for brown hair and blonde hair, his sperm cells can contain the instructions for either (only one will be passed to his offspring)

20. Law of segregation

21. Law #3Law of Independent Assortment • States that the assortment of chromosomes for one trait does not affect the assortment of traits for another chromosomes for another trait. • You can pass on any combination of maternal and paternal chromosomes.

23. Punnett Squares • The Laws of Segregation and Independent Assortment helped to develop a tool for predicting the probability of passing on certain combinations of alleles. This tool is called a Punnett Square.

24. Example of how the Rules Work: • Brown hair (B) is dominant over blond hair (b). Mom is heterozygous (Bb) and Dad is homozygous recessive (bb). • The Law of Segregation tells us that each parent will only pass on ONE of the alleles (letters) to their offspring. • The Law of Independent Assortment tells us that we can look at this trait independently because its inheritance is not related to the inheritance of other traits.

25. What is a Punnett Square? • A Punnett Square is simply a tool to help you understand how alleles are passed to the next generation.  • It enables you to follow each parental allele as it could get passed to the next generation.

26. What is a Cross? • The crossing of an egg and a sperm from two individuals • For example: • Bb x bb

27. Rules for Punnett Squares: • The dominant allele is written first. • Typically use the first letter of the dominant allele for the trait. (B) • The recessive allele is the lower case of the dominant allele. (t) • Separate Mom’s and Dad’s alleles—put one letter over/next to each box • Combine each of their alleles (one from each) into each grid box • The outcome allele combinations represents the parent’s offspring (or zygote) Link to a helpful tutorial on how to use punnett squares: http://www.wikihow.com/Work-With-Punnett-Squares

28. Monohybrid Cross • Examines the inheritance of one trait • There are three types of monohybrid crosses: • Homozygous x Homozygous TT x TT tt x tt • Heterozygous x Homozygous Tt x TT Tt x tt • Heterozygous x Heterozygous Tt x Tt

29. This shows the probability of passing on a specific combination of alleles (in the example – 50% chance of Bb, 50% chance of bb). • However, this only represents ONE OFFSPRING! This does not mean that this set of parents will have 2 children with brown hair and 2 children with blond hair. • Each child will have the same chance (50/50 in this case) of having brown or blond hair. • Example: Bb x bb • B=brown hair • b=blonde hair B b b b

30. Try crossing a homozygous recessive with a homozygous dominant individual Genotype Ratio: Phenotype Ratio:

31. Try crossing two heterozygous individuals. Genotype Ratio: Phenotype Ratio:

32. Try crossing a heterozygous individual with a homozygous recessive one. Genotype Ratio: Phenotype Ratio:

33. Magic or Muggle? • The allele for being a muggle is M. • The allele for wizarding ability is m. • M is dominant to m so you can only be a wizard if you have the recessive alleles.

34. Harry Potter Punnett Squares • Hermione’s only possible genotype is mm, because she is a wizard. What would be the possible genotypes of Hermione’s parents who are both Muggles?

35. Harry Potter married Ginny Weasley. What is the chance that their children will have magical ability?

36. Wake Up Work #1 • Harry has brown hair like his father did, but his mom had red hair. If B=brown hair and b= red hair, what could Harry’s genotype be? Show your Punnett square and the phenotype and genotype ratios.

37. 4/1/14 • Go over pages 16-18 • Dihybrid crosses • Practice

38. Dihybrid Cross • Shows the inheritance of TWO different traits

40. Cross two individuals who are both heterozygous tall (Tt) and heterozygous red (Rr). Determine the phenotypic ratio.

41. A male rabbit with the genotype GgBbis crossed with a female rabbit with the genotype GgBb. Determine the phenotype possibilities of the offspring. G=gray g=white B=blue eyes b=brown eyes

42. Work on pages 19-21 • this will be turned in for a grade

43. Dihybrid Cross Tutorial • http://www.sophia.org/tutorials/dihybrid-cross