Genetics!!!

1. Genetics!!!

2. First… • Some Background Information…

3. What is heredity? • Heredity is the passing of traits from parent to offspring. • You inherit traits from your parents

4. What are traits? Ex. Include: • Eye Color • Hair Color • Height • Weight • Body Structure • Facial Features • Skin Color http://www.dance-classes.ca/photos/faces/faces_2004W_comp1.jpg

5. What traits did you inheritfrom your parents? • Turn to the Activity: Genetic Traits Taking a Class Survey” in your Packet. • You will have 7 min. to complete the chart • Be prepared to share the information with your class.

6. How are traits passed? • When organisms reproduce, traits are passed from parent to offspring. • These traits are carried in DNA, the genetic material found in a cell’s nucleus. • DNA acts like a blueprint. publications.nigms.nih.gov

7. http://www.healthsystem.virginia.edu/internet/huntdisease/i mages/DNA.gif

8. Gregory Mendel’s Genetics • Father of Genetics • Studied how traits or characteristics are passed from parents to offspring called hereditary • Is most known for his • experiments with • thousands of • pea plants to learn • about genetics

10. Mendel’s Experiments: • Crossed plants with opposite traits • ex. Tall plants w/ short plants • Crossed purebreds – always produce offspring with the same trait • Crossed : • Parents: green plant x yellow plant = all green (F1 generation) • F1 generation: green x green = green and yellow (F2 generation)

12. Dominant and Recessive Alleles: One trait can hide or mask another trait Dominant trait – the trait that always shows up when the allele is present, hiding the other trait Recessive trait – the trait that is hidden or masked whenever a dominate allele is present Some traits are dominate, some are recessive

13. Heterozygous vs. Homozygous • Heterozygous: • 2 different alleles for a specific trait • Ex. Tt, Bb (Capital = Dom., lower case= rec.) • Pure/Homozygous: • two of the same alleles for a specific trait • Ex. tt, BB (Capital = Dom., lower case= rec.) • Homozygous recessive = 2 lower case letters • Homozygous dominant = 2 capital letters

14. Chromosomes How do we know what something will look like? • Ans. In the genes and the alleles of the organism • Genes – small piece of DNA for a trait • Alleles provide the “code” for a specific trait

15. Alleles: Carry specific information regarding a trait: Ex. • Gene eye color • Alleles for eye color blue vs. brown • And height (gene) in pea plants: • Tall pea plant (allele)= T dominant trait (capital letter) • Short pea plant (allele) = t recessive trait (lower case)

16. Homologs & Alleles • organisms have a chromosome received from each parent. • Called homologous chromosomes • This ex. has alleles of A, B, C & D. • A & a, B & b, C & c, D & d • A, B, C & D are at specific loci (location)

17. How did Mendel cross plants to get variation (differences) in the offspring? Ans. He manipulated the pollination (fertilization) process of various traits in the flowers of pea plants. • Reproductive structures of a flower: • Male Structures = anther and filament (pistil) • Female Structures = stigma, style and ovary (style)

18. The Reproductive Structures of a Flower: Pistil

19. Genetics and Probability Punnett Squares: • A chart showing all possible combinations. • Used to determine probability of an out come • Cross between 2 alleles • One set across top • One set down left hand side • Boxes = possible combinations

20. Phenotype and Genotype • Phenotype - how it looks. Examples tall short, blue, black. - the visible outcome of the alleles - Ex. 75% Tall, 25% short ( not tall) • Genotype – = the alleles represented in the Punnett square - Ex. 25% Tt, 50 % TT, 25% tt - genetic make-up. - Allele combinations ex. TT, Tt, tt • Homozygous-2 same alleles for a specific trait • Homozygous recessive  tt • Homozygous dominate  TT. • Heterozygous – 2 different alleles for a trait  Tt, Bb.

21. Using a Punnett Square: • Used to determine probability • (Probability = the likelihood a particular event will happen.) • Example of a Punnett Square crossing 2 parents Tt : • Out come 1-TT, 2- Tt, 1- tt

22. Predicting Probability • Using alleles offspring can be predicted: Pure dominate – TT X Pure recessive - tt = • All offspring will receive a dominant allele • 100% will show the dominant trait • Can you create another cross and predict the out come? • the visible outcome of the alleles • Ex. 75% Tall, 25% short ( not tall)

23. Predicting Probability Crossing 2 heterozygous parents always gives the ratio…

24. Punnett Square Examples: • In rabbits, black (B) fur is dom. to white (b). Cross a homozygous black fur w/ a heterozygous rabbit. Identify the genotypes and phenotypes.

25. LAB: Genetics with a Smile  • Turn your packet to the page titled: • Genetics with a Smile. • With a partner, you will construct Punnett squares to determine the outcome of your youngin’…  • Complete at home as needed!!!!

27. Section 10.1 Summary – pages 253-262 The law of segregation • The law of segregation states that every individual has two alleles of each gene and when gametes are produced, each gamete receives one of these alleles. • During fertilization, these gametes randomly pair to produce four combinations of alleles.

28. Section 10.1 Summary – pages 253-262 Phenotypes and Genotypes Law of segregation Tt´Tt cross • Two organisms can look alike but have different underlying allele combinations. F1 Tall plant Tall plant T t t T F2 Tall Tall Tall Short t t t t T T T T 3 1

29. Section 10.1 Summary – pages 253-262 The law of independent assortment • Mendel’s second law states that genes for different traits—for example, seed shape and seed color—are inherited independently of each other. • This conclusion is known as the law of independent assortment.