Understanding Genetics in Organisms - Explore Mendelian Traits and Inheritance Patterns

1. Chapter 4 - Modern GENETICS Cells and Heredity Textbook

2. Gregor Mendel did a lot to initiate and progress the Genetics--study of heredity. • What organisms did Mendel study? He studied pea plants. Why were traits in pea plants (like tallness)easy to study? These traits were clearly defined—like tall and short, green or yellow, wrinkled or smooth. There is often a definite dominant and definite recessive trait. A Single gene with 2 alleles controls a trait.

3. REVIEW of TRAITS:One of the most important principles that governs life is inheritance of genes. There are over 200 traits that are transmitted from generation to generation in humans. The physical traits are those that are expressed and what makes every individual an 'individual'. These genes reside on specific segments of the DNA. Each gene is grouped to form a chromosome and each chromosome is found in the nucleus of the cell. There are two copies of each gene present in an individual's body with the exception of sex cells.It is generally believed that the dominant alleles are the most common traits observed in a population. However, this is not a complete fact. Many times the alleles may be dominant, but the allele for expression of a trait may be recessive. Thus, many times the dominant trait is not expressed in an individual. Let me explain this inheritance pattern in the following examples.

4. Now , we are going to look at: • “Mendelian” traits in humans. • Many of these traits have been claimed to be controlled by ONE gene with just 2 alleles. As we continue to learn more, some scientists disagree.

19. As you can see…. • Traits like hitchhikers thumb, mid-digit hair, cleft-chin, curly hair, handedness, etc are examples of… • “Mendelian Inheritance” • What is mendelian inheritance??? Traits are controlled by a single gene with 2 alleles, and one alleles is generally dominant over the other.

20. HOWEVER…… • There are a variety of inheritance patterns for the many traits that humans have. • Right now , brainstorm traits that are more complicated than “Mendelian traits” Ex: height, skin color, eye color, hair color, metabolism, body build, etc.

21. Some Inheritance Patterns • 1. Single gene with 2 alleles • 2. Single Gene with multiple alleles • 3. Traits controlled by many genes • 4. Sex – linked genes

22. Single Genes with Multiple Alleles • These genes have 3 or more forms (alleles). • Humans can only carry 2 of them • Ex: Blood • Alleles: • IA, IB, I • IA and IB are codominant • Blood Types • A, B, AB, O

23. Traits controlled by many genes • At least 4 different genes control height • 3 or more genes control skin color

24. Sex Chromosomes carry genes that determine whether a person is male or female, and some other traits. • XX = female • All female sex cells have an X chromosome • XY = male • Half of the male sex cells have an X chromosome and half have a Y chromosome

25. Sex Linked Genes • These genes are carried from parent to offspring on the sex chromosomes. • Sex-linked traits • Ex: red/green colorblindness • Occur more often in males.

26. If there is a sex-linked trait controlled by a recessive allele, • If a guy gets it, he will have the trait because he only has one X chromosome. • If a girl gets it, there’s a good chance her other X chromosome will be normal and she will not express the trait.

27. Ex: Colorblindness • It’s a trait controlled by a recessive allele on the X chromosomes • Carrier = a person who has one recessive allele for a trait and one dominant allele. They do not have the trait.

28. Effect of Environment • Many of a person’s characteristics are determined by an interaction between genes and the environment • Ex: bad dietaffects height • Ex: hair dye

29. DO NOW • Pg 117 Discover Activity

30. Human Genetic Disorders • Genetic Disorder = abnormal condition that a person inherits through genes or chromosomes • Caused by • mutations in DNA • Change in overall structure of chromosomes • Change in number of chromosomes

31. Genetic Disorders • Cystic Fibrosis • Sickle-cell disease • Hemophilia • Down syndrome

32. Cystic Fibrosis

33. Sickle-Cell Disease

34. Hemophilia

36. Down Syndrome

38. Pedigrees • A chart or “family tree” use to track witch members of a family have a particular trait

39. Which trait do you think is dominant? Which is recessive?

40. Managing Genetic Disorders • Doctors use tools such as karyotypes to help diagnose genetic disorders. • People with genetic disorders are helped through medical care, education, job training, and other methods

41. What’s a Karyotype?? • It’s a picture of all the chromosomes in a cell. Chromosomes are arranged in pairs. • They can reveal whether a person has the correct number of chromosomes.

42. Sec 3 - ADVANCES IN GENETICS • Genetic Techniques to produce organisms with desirable traits: • 1. Selective Breeding • 2. Cloning • 3. Genetic Engineering

43. 1. Selective Breeding HISTORY: • In Mexico thousands of years ago, Mexican farmers saved seeds from the healthiest corn plants each year. Then, in the spring, they planted those seeds. After a while, plants produced better corn and crops were improved.

44. SELECTIVE BREEDING Inbreeding

45. SELECTIVE BREEDING Hybridization • Cross 2 genetically different organisms so that the offspring will have the best traits from both. • Ex: cross a McIntosh apple with a Red Delicious to get Empire.

46. 2. Cloning • Clone = organism that has exactly the same genes as the organism from which it was produced • PLANTS: • African violet, just cut a stem from one plant and put it in soil. • ANIMALS: • Sheep and pigs have been cloned

47. 3. Genetic Engineering • Genes from one organism are transferred into the DNA of another organism. make medicines improve crops

48. Genetic Engineeringin Bacteria • Pg 126

49. Genetic Engineering… • Scientists take human genes and insert them into cells of cows so that they start to produce a human protein in their milk. This protein is needed by people with hemophilia.

50. Genetic Engineering…… • Scientists insert genes into the cells of plants like tomatoes and rice so that they will survive despite cold temperatures or poor soil.