Unraveling Genetics: Decoding Traits Through DNA

1. Genetics and Inheritance Chapter 11 (page 262)

2. What makes you you? DNA • DNA is a system of codes that controls every aspect of your life (how you look, how you act, etc.) • DNA is like the instruction manual to keep you working.

3. DNA gene Gene = one section of DNA that controls one specific trait. (Examples: Hairline gene, earlobe gene, etc.)

4. DNA gene  chromosome Chromosome = 1 strand of DNA that is condensed/squeezed into a rod shape

5. DNA gene  chromosome

6. Every living things inherits traits, or characteristics, from its parents. How are these traits passed from one generation to the next? The answer lies in the study of genetics.

7. Mendelian Genetics Essential Question: "How can two brown fur rabbits have a white fur baby?"

8. Genetics Definition = The branch of biology that studies heredity. (Heredity = biological inheritance)

9. ~Austrian monk ~In charge of the monastery garden~Experimented with pea plants Gregor Mendel “Father of Genetics” Gregor Mendel    1822-1884  

10. Mendel observed seven traits that are easily recognized and apparently only occur in one of two forms:

11. Mendel knew an important fact of his pea plants: The flowers have both male and female reproductive parts.

12. Pollination • Pea plants contain both male and female parts, so they can produce seeds by… SELF-POLLINATION • Fertilization of a plant’s egg cells by the pollen of another plant = • CROSS-POLLINATION

15. Terminology: • 1. Gene- a section of DNA that controls a specific trait • Allele– alternative form of a GENE • Trait—a characteristic of a species determined by specific genes

16. Dominant gene—the presence of this type of gene will mask/hide the other gene • Recessive gene—this gene is hidden by the other gene unless there are two copies of the recessive form.

17. Video from: http://ed.ted.com/lessons/how-mendel-s-pea-plants-helped-us-understand-genetics-hortensia-jimenez-diaz

18. Results By breeding many plants over and over, he found that "statistically" certain traits appeared with a certain probability

19. Mendel’s Results and Conclusions: • Biological characteristics are determined by genes. • (Genes are passed from parents to their offspring.)

20. Mendel’s Results and Conclusions: • Some forms (alleles) of a gene may be dominant and others may be recessive.

21. Mendel’s Results and Conclusions: • In most sexually reproducing organisms, each adult has two copies of each gene—one from each parent. These genes are segregated/separated from each other when gametes are formed. (Law of Segregation)

22. Mendel’s Results and Conclusions: • The alleles for different genes usually segregate independently of one another. (Law of Independent Assortment)

24. Terminology continued: 6. HYBRID–offspring of parents with different traits 7. Homozygous - both pairs of genes for a specific trait are the same 8. Heterozygous - both pairs of genes are different

25. Terminology Con’t… 9. Genotype – the genetic makeup of an organism (ie. AA, Aa, aa) 10. Phenotype – the physical appearance of an organism (ie. Hair color, eye color, etc.)

26. Monohybrid CrossesA cross between individuals that involves ONE pair of contrasting traits

27. Punnett Squares!!!= tool used to determine the probability of offspring of a cross between two parents

28. Punnett Squares Can be used to predict & compare the genetic variations that will result from a cross = DOMINANT = DOMINANT (capital letter) Punnett B MonoHybrid Cross Squares = recessive = recessive (lower case) b

29. Punnett Squares Can be used to predict & compare the genetic variations that will result from a cross = DOMINANT = DOMINANT (capital letter) HOMOzygous = organisms that have 2 IDENTICALalleles for the same trait Punnett B Squares = recessive = recessive (lower case) HETEROzygous = organisms that have 2 DIFFERENT alleles for the same trait b

30. Probability The likely hood that a particular event will occur Punnett Squares Segregation

31. Test Cross • To determine the GENOTYPE of an organism expressing the dominant phenotype. • Testcross= a mating between an individual with an unknown genotype and an individual that is HOMOZYGOS RECESSIVE. – Look at offspring to determine parent genotype • Example: Labrador Retriever • B- back fur • b= chocolate brown fur Black lab X chocolate lab B___ X bb

32. Test Cross Example • In humans, long eyelashes is (E) is dominant short eyelashes (e). • A man with long eyelashes marries a woman with short eyelashes and they have three children, two of whom have long eyelashes and one of whom has short eyelashes. • Draw the Punnettsquares that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?

33. Dihybrid CrossesA cross between individuals that involves TWO pairs of contrasting traits

35. Patterns of inheritance

36. One allele can completely hide the other (Mendel traits) 1. Complete Dominance

37. 2. Incomplete Dominance Flower Color in Snapdragon =both alleles influence the phenotype (blending)

38. Incomplete dominance in humans

39. 3. Codominance = neither alleles totally masks the other RR = red hair rr = white hair Rr = roan (red AND white hairs present) (both traits are seen—spotting)

40. Most common blood type Codominance and multiple alleles

41. 4. Polygenetic One trait is controlled by multiple genes Examples: Height, skin color

42. 5. Pleiotropy One gene affects multiple traits • --In humans these usually present themselves with disease. • Example: sickle cell disease