Understanding Genetics: Heredity & Mendel's Pea Plant Experiment

1. Genetics The science that relates to the study of genes and the patterns of heredity

2. Please don’t talk over the lesson….raise your hand if you have a question to make. Thank You

3. Heredity The passing of traits from parents to offspring. A puppy gets its traits from its parents just as we get ours from our parents, but just how are traits inherited?

5. KARYOTYPE- a picture of all the chromosomes in a nucleus Each human has 46 chromosomes located in their body cells nucleus of the cell (diploid cells) These are divided into 23 chromosomes- a baby inherits one chromosome from each parent from each pair of chromosomes

6. Of the 46 total chromosomes, two of them are sex chromosomes. XX- female Xy- male

7. A piece of DNA on a chromosome is called a gene. Genes also come in pairs. They determine many of the characteristics of a baby.

9. Gregor Mendel • Gregor Mendel is known as the father of genetics • He was born in Austria in 1822 • He grew up on a farm and learned a lot about flowers and trees • When he was 21 yrs old he joined a monastery and became a monk. As a monk he taught science and performed scientific experiments

10. Mendel spent most of his time and energy performing experiments with pea plants • He was very curious as to how offspring inherited their traits • He used pea plants in his experiments because peas had many desirable traits that made them easy to work with

11. Peas were a good choice because • They grow quickly • They come in many varieties with easy to observe traits: round, wrinkled, yellow, green, smooth bumpy, tall, short • Some cross pollinate, others self-pollinate • Self –pollination was important because Mendel was able to grow true- breeding plants for his experiments GREGOR MENDEL USED PEAS FOR HIS EXPERIMENTs- WHY?

12. Mendel noticed that one trait was always present in the first generation and the other one seemed to disappear • He called the trait that appeared the dominant trait and the trait that seemed to fade away the recessive trait • To find out what might have happened to the recessive trait, Mendel decided to perform another set of experiments

13. P stands for the parents of the first generation (purple flower crossed with white flower) F1 stands for the offspring of the a self of the purebred cross above. F2 stands for the offspring when an F1 flower is self-fertilized were crossed.

14. Brown eyes is a dominant trait, so we would write the genotype for brown eyes as BB, Bb Blue eyes is a recessive trait. The only way to show a recessive trait is to have a genotype with two recessive alleles, such as bb

15. Alleles • An allele is a variation of a gene: BB, Bb, CC, Cc, cc, DD, EE, ee Some alleles are dominant and some alleles are recessive. Dominant alleles are represented by capital (A) letters in genetics, and recessive alleles are represented by lower case letters (a)

16. Alleles, are variations of a gene, and they usually come in pairs. Alleles determine the appearance of our characteristics There are at least two alleles for every characteristic If the two alleles are the same then it is said to be homozygous for that gene If they are different then they are heterozygous

17. Homozygous means the same and heterozygous means different.

18. Genotype and Phenotype • Genotype is the combination of alleles that code for a specific trait DD for example could be the genotype for having dimples. • Phenotype is the physical appearance that the genotype codes for. • Dimples is a phenotype. What is a phenotype that you have?

19. PHENOTYPES Your adorable smile, the shape and color of your eyes, and your hair texture are just a few examples of phenotypes

20. We know that genes determine our smile, but what about personality? Yes, some of our personality is hereditary, but part of it is also a result of the environment we are exposed to as a child Nature vs. Nurture

21. Homozygous and Heterozygous Genotypes • Homozygous genotypes with either all dominant alleles or all recessive alleles (think: the same) • DD, dd, cc, CC, EE, ee, FF, gg, GG, dd, DD • Heterozygous genotypes have at least one dominant allele and one recessive allele • (think: different) • Dd, Ff, Gg, Ee, Ee, Cc, Gg, Rr...

22. Punnett Squares predict the possible genotypes of offspring in a particular cross using the genotypes of the parents

23. What color feathers will the offspring in the test cross below have?

25. PTC tasting is a dominant trait

27. A brown furred rabbit (Bb) mates with a white furred rabbit (bb). What is the probability that they will have dark-furred offspring?

28. Answer: • Approximately 50% of their offspring will be dark-furred, with a heterozygous (Bb) genotype. • What percent would likely have the recessive phenotype of white fur? • To show the recessive trait, the offspring must have inherited two recessive alleles (bb), one from each parent. They also have a 50% chance of having white furred bunnies…..

29. Punnett Square Problem • Two brown furred rabbits with the genotypes Bb mate and produce ¼ offspring that are light furred with the genotype bb. How is this possible?

30. Answer • The ¼ offspring received one recessive allele from each parent giving them a recessive trait

31. True or false A puppy receives half its genes from its mother and half from its father

32. Incomplete Dominance An inheritance pattern where neither allele is dominant, but instead the phenotype of the offspring is in between both homozygous genotypes In this case, the R allele codes for a red color, so the more of this of this protein, the more red the petal color

33. Codominance • An inheritance pattern where neither allele is dominant, but rather they share dominance, and thus, the offspring will have traits of both alleles if it inherits one of each

34. Human blood type is determined by codominance There are three alleles for blood type. We inherit two from our parents. IA and IB share dominance and i is recessive See chart to the side…. A person with alleles A and B is neither A or B blood type, but rather, blood type AB. A person must have two i alleles to have blood type O because O blood type is a recessive trait.

35. Type A and B individuals can be either homozygous (IA,IA, or IB, IB), or heterozygous (IA i, or IB i) A person must have two i alleles to have blood type O

36. A woman with blood type A and a man with type B blood could potentially have offspring with which of the following blood types?

37. Multiple Genes • Some traits, such as hair, eye and skin color are determined by multiple genes, giving a wide variety in the colors produced

38. Environmental Influences • Some genes can remain unexpressed until something in the environment influences it • For example, some people have a gene for developing lung cancer that may not be expressed unless the person is exposed to the chemicals in tobacco • The Himalayan rabbit has a gene for fur color that produces dark fur, but it is only activated at cooler temperatures, which is why the cooler body parts, like ears and nose are black.

39. These Rabbits have a gene that causes fur color to be black if exposed to low temperatures

40. EYE COLOR • Different eye colors are produced because of the different amounts and patterns of pigments in the iris (colored part of the eye), which is determined by one’s genetic make up • The DNA inherited from one’s parents determines what color eyes they will have • Right now there are three known gene pairs that control eye color, and at least two are incompletely dominant

41. The bey 2 gene on chromosome 15 has a brown and blue allele • On chromosome 15 the bey 1 gene contains the central brown gene • On chromosome pair 19, the gey gene contains a blue allele and a green allele

42. BB Xbb All children with Bb genotype Bb X Bb Possible genotypes: BB,Bb,Bb, bb

43. Can two brown-eyed parents have a blue-eyed child? Explain and show your work.

44. Yes, if both are heterozygous for brown eyes and the child inherits a recessive allele from each parent. There is 25% chance…

45. A green allele is dominant to a blue allele • And brown allele is dominant to both a blue and a green allele • For the bey 2 gene if a person has a brown allele then they will have brown eyes • In the gey gene the green allele is dominant to the blue alleles but still recessive to brown • A person will have green eyes if they have a green allele on chromosome 19 and all or some blue alleles • Blue eyes is produced by having only recessive genes • So for a blue eyed person all four alleles have to be blue

46. If two parents have a blue and a brown gene, there eyes are brown, but they can have a blue eyed child if the child inherits a blue gene from each parent • If the child inherits one blue gene and one brown gene the child will have brown eyes, because brown is dominant to blue

47. Heterochromia- condition where a person has two different colored eyes

48. What are the causes of heterochromia? • Disease or injury to that affects the health of the melanocytes (cells in the eyes that produce eye colors) • Wardenburg Syndrome- A mutation in certain genes that causes melanocytes to get lost on their way to where they are supposed to go • Chimarism (very rare!)- when two fertilized eggs fuse to form one egg, each with a different set of DNA

49. David Bowie

50. Genetic Disorders • A genetic disorder is one that is caused by abnormalities in the genes or chromosomes • While some diseases, such as cancer, are caused by genetic abnormalities in some cells, a “genetic disease” is one that is present in all cells and has been present since conception • When something goes wrong with the chromosomes in processing a new human being, the code cannot be read properly and the child’s brain and body may not develop properly. When a problem results from this genetic mistake, we call is a genetic disorder.