Mendel and Meiosis

1. Mendel and Meiosis Chapter 10

2. Section 10.1Mendel’s Laws of Heredity • Heredity: the passing of characteristics from parents to offspring. • Genetics: study of Heredity • Traits: Inherited characteristics. • Gene:is a region of genetic information on a chromosome that “codes” for a certain trait

3. Gametes: The sex cells found in an individual- egg or sperm. • Fertilization: The uniting of male and female gametes. • Zygote: fertilized cell

4. Pollination: The transfer of pollen grains from a male reproductive organ to a female reproduction organ. • Sperm: Male gamete • Egg: Female gamete Cross Pollination Self-Pollination

5. Father of Genetics • Gregor Mendel (1822-1884): An Austrian monk. He wanted to know how traits were passed from parent to child.

7. Mendel’s Research • Mendel did many experiments with pea plants and bred them for certain traits • Mendel started out with plants that he knew were only tall or short. • He mated short plants with tall plants. • All the offspring were tall!! • What was going on??? To investigate he bred these plants over and over again and recorded his results!

8. Mendel’s Experiments

9. Mendel’s experiments • In his work he named the different generations of plants: • The Parents: P1 generation • The first generation of offspring: F1 generation • The second generation of offspring: F2 generation

10. Mendel’s Laws • Law of Segregation: the members of each pair of alleles separate when gametes are formed. A gamete will receive one allele or the other

11. Law of Independent assortmentstates that when gametes are made, the genes for traits found on different chromosomes separate independently Animation

12. Basic Genetics • Remember: DNA twisted into chromosomes, chromosomes have genes on them, for each gene there are different forms or alleles of that trait Alleles: A form of a gene, one comes from the mother, one from the father. • Ex. Gene = height, the allele could be tall or short. Gene = eye color, the allele could be light or dark. We have 2 alleles for each trait (one from mom, one from dad)!

13. Draw me in your notes and write down the info!!

14. If there are two alleles, and only one observed trait, which allele is dominant? • A dominantallele is always expressed. • Write the dominant allele in capital letters • A recessive allele; • not expressed when in the presence of a dominant allele. • is expressed when paired with another recessive allele. • Write the recessive allele in lower case letters t T Dominant Recessive

16. Phenotype: The expression of the gene itself. (what we see) • Blue eyes, straight hair, brown hair are all phenotypes. Genotype: The combination of alleles for a trait. (your actual DNA) Ex. B = brown eyes b = blue eyes Genotype: Bb Phenotype : brown eyes

17. So we know about genes and traits… how can we predict what our offspring will look like? Punnett Squares tell us the probability that the offspring will look a certain way!!

18. Punnett Squares: a diagram used to identify possible combinations of dominant and recessive alleles in offspring Mom Dad - A is a dominant characteristic. - This bird has two genes for red feathers. - Its genotype is AA. - Its phenotype is red - a is a recessive characteristic. - This bird has two genes for blue feathers.   - Its genotype is aa. - Its phenotype is blue

19. Setting up your Punnett square • Possible Offspring: 4 Red Because Red is dominant!

20. Homozygous: Two of the same allele for a trait. • Ex: AAoraa • Heterozygous: Two different alleles for one trait. • Ex: Aa • AA is homozygous dominant. • aa is homozygous recessive. • Aa is heterozygous.

21. Punnett Squares (cont’d) • Monohybrid cross: means“one gene”. Each parent donates one allele to the offspring

24. Dihybrid Cross (Two factor cross) • Each parent donates two alleles to the offspring

25. Genetic Exceptions to the rules! Incomplete Dominance • One allele is not completely dominant over the other. • Example: Cross red (RR) flower with a white (WW) flower. The resulting RW flower is pink.

26. Genetic Exceptions to the rules! Codominance • Both alleles contribute to the phenotype • Example: A red cow crossed with a white cow results red cows with white blotches.

27. Genetic Exceptions to the rules! Multiple Alleles • A gene has more than one allele • The result is various expressions of the gene. • Example: various hair colors in mice.

28. Genetic Exceptions to the rules! Polygenic Traits • Traits controlled by more than one gene • Ex. Human skin color • More than 4 different genes control this trait, which is why we all look so different!

29. Genetics and the Environment • Depending on the trait.. Your environment can affect your phenotype! • Ex. If you are out in the sun, your skin color may change • Ex. If you smoke, you increase your risk of lung cancer