Introduction

1. Introduction • Genetics: the study of the transfer of traits and hereditary material from parents to offspring. • Asexual reproduction: The offspring is exactly copy of the parent. Only one parent is involved. • Sexual reproduction: Two parents are involved. -Genes from 2 organisms (parents) of the same species get mixed. sex cells = gametes = sperm and ova

2. What is the purpose of sexual reproduction? • Greater variety • Why are animals diploid (2 copies of each chromosome)? • Most of “genetics” is based on the fact that animals have 2 copies of each gene. • What is the purpose of meiosis: • To keep the chromosome number constant

3. Diploid (2n): having 2 sets of chromosomes • Haploid (1n): having 1 set of chromosomes • Homologous chromosomes have the same genes.

4. Meiosis • Meiosis is cell division which produces gametes. • Meiosis cuts the chromosome number in half. -Example: a human body cell has 46 chromosomes and a human sex cell has 23 chromosomes • Meiosis occurs after DNA replication, and contains two cell divisions ( Meiosis I and Meiosis II), with no Interphase between them.

5. Meiosis l – homologous chromosomes separateThis results in 2 daughter cells that are NOT the same(DON’T NEED TO KNOW ALL DETAILS)

6. Meiosis ll – similar to mitosis: sister chromatids separate (DON’T NEED TO KNOW ALL DETAILS)

7. Crossing over provides more genetic variation Occurs at prophase of Meiosis I

8. Genetics Gregor Mendel observed pea plants with different traits ( flower color, plant size, pea shape..)

9. Self-pollination • Most plants produce both sperm and ova • Pea plants can self-pollinate. • Self pollination leads eventually to pure –bred plants. • Pure-bred plants produce offspring exactly like themselves (if self-pollinated). • Mendel crossed various pure-bred plants.

10. Life Cycle of the Pea Plant

11. Cross-Pollinated Plants

12. Dominant and Recessive Traits • A dominant trait overshadows a recessive trait. • Mendel crossed yellow seeds x green seeds. All offspring had yellow seeds. He did not get plants with green seeds.

13. P – parental generation • F1- first filial generation (from 2 purebred parents) • F2- second filial generation (F1 X F1)

14. Mendel then crossed the F1 offspring among themselves. In the F2, he got 3/4 yellow seeded plants and ¼ green seeded plants.

15. Mendel’s conclusions • There are 2 alternative forms of a gene, one for green seeds and one for yellow seeds. These 2 forms are called alleles. • Peas have 2 alleles of each gene. • Yellow is dominant and green is recessive.

16. Modern Genetics • Genes are segments of DNA on a chromosome that make a particular protein that is responsible for a particular trait (seed color, skin color, eye color, type of hair, etc.)

17. Homozygous is an organism with two identical alleles of a gene for a given character: - YY (yellow) or yy (green). • Heterozygousis an organism that has different alleles for a character: Yy. Only the dominant gene will be expressed.

18. • Phenotype is an expressed, observable trait. • Example: color of the seed, yellow phenotype and green phenotype. •Genotype is the combination of specific alleles in the offspring. - Example: YY and Yy genotypes for yellow color, and yy genotype for green color.

19. The Punnett Square It demonstrates simple genetic possibilities and probabilities in chart form. Parent’s alleles are placed on both sides of the chart

20. The Punnett Square

21. F2 Phenotype and genotype ratio

22. Phenotype ratio in a Dihybrid Cross(DON’T NEED TO KNOW DETAILS)

23. The Law of Independent Assortment • The traits are not stuck together. They sort independently.

24. Probabilities • Rule: probabilities of events that must happen at the same time are multiplied • Coin: H-head h-tails 1. Coin # 1 H probability ½ ( 50%) Coin #2 H probability ½ (50%) • Probability for HH: ½ x ½ = ¼ ( 25%) 2. Probability for hh: (25%) 3. Probability for Hh: (25%) 4. Probability for hH: (25%) 5. Hh and hH are basically the same. To calculate the probability of one head and one tail, add the two separate probabilities.  • ¼ + ¼ = 2/4 (50%)

25. In a 4-person card game in which all the cards are dealt out, what is your chance of getting the king of spades? • What is your chance of getting the king and ace of spades? • What is your chance of getting the queen, king and ace of spades?

26. Pedigree Chart-Genetic History of a Person Carrying a Mutation

27. Using eye color (blue recessive or brown dominant), what conditions would prove that a man is not the father of a child?

28. Answer • If child has brown eyes, and both man and mother have blue eyes.

29. Polygenetic Inheritance • More then one gene determines a particular trait. Examples: wheat grain color, skin color, body height. • Such a trait exist in a range (it does not come in just two variations).

30. Sex Determination • X and Y chromosomes are a pair, but they do not carry the same genes. The Y chromosome is much smaller. • XY - male individual • XX - female individual • So the Y chromosome makes a person a male • Females have 2 X chromosomes, but males have only 1.

31. Genes linked to the X sex chromosome • Sex chromosomes also carry genes for other traits. The X chromosome carries many more genes than the Y chromosome. • Since a male has only one X chromosome, all genes on that chromosome will be expressed. • A bad gene on the X chromosome is much more likely to be expressed in a male than in a female.

32. My father was color blind (X-linked recessive). • I am not, but do I have to worry that my children will get my father’s color blind gene from me? • If I had a sister, would she have to worry about this?