1. Chapter 3 Part 2 Sections 7-12

2. SECTION 3-7 What are incomplete dominance and codominance?

3. Key terms! Incomplete dominance- pattern of inheritance in which alleles from both parents are blended Incomplete dominance- pattern of inheritance in which alleles from both parents are blended Codominance- patter of inheritance in which both alleles of a gene are expressed Codominance- patter of inheritance in which both alleles of a gene are expressed

4. Incomplete Dominance In simple dominance, one allele is dominant over another. In simple dominance, one allele is dominant over another. There are special cases, however, when there is no completely dominant trait. This is called incomplete dominance. There are special cases, however, when there is no completely dominant trait. This is called incomplete dominance. – When this happens offspring will show a blending of traits from each parent.

5. Incomplete Dominance Incomplete dominance can been seen is many organisms. Incomplete dominance can been seen is many organisms.

6. We can still complete a Punnett square for these cases, to determine the probability of what the offspring will be like. We can still complete a Punnett square for these cases, to determine the probability of what the offspring will be like. Now, instead of having a capital and a lowercase letter. We will have two capital letters for both alleles! Now, instead of having a capital and a lowercase letter. We will have two capital letters for both alleles!

7. For Example There is a flower called the four o’clock flower, which gets it’s name for the time of day that the flowers open, shows incomplete dominance. There is a flower called the four o’clock flower, which gets it’s name for the time of day that the flowers open, shows incomplete dominance. RR- are red plants RR- are red plants WW- are white plants WW- are white plants RW- are pink RW- are pink

8. It looks like this

9. A different type of dominance is codominance. A different type of dominance is codominance. – This happens when both alleles of a certain trait appear in the offspring. As with incomplete dominance, codominance neither dominant allele is dominant over each other. As with incomplete dominance, codominance neither dominant allele is dominant over each other. IT IS NOT THE SAME AS INCOMPLETE DOMINANCE!!! IT IS NOT THE SAME AS INCOMPLETE DOMINANCE!!! Codominance

10. Codominance in Chickens In some chickens there is a gene for black feathers (B) and there is a gene for white feathers (W). In some chickens there is a gene for black feathers (B) and there is a gene for white feathers (W). A chicken that has: A chicken that has: – Black feathers is BB – White feathers is WW – Both black and white is BW* *This is the heterozygous form. *This is the heterozygous form.

12. Heterozygous Crosses When crossing two organisms showing incomplete dominance you will have 3 categories that the offspring fall into. When crossing two organisms showing incomplete dominance you will have 3 categories that the offspring fall into. It looks like this: It looks like this:

13. 3-8 How is gender determined?

14. Key Terms Gender – sex of a person or other organism

15. X and Y In people, there are 23 chromosomes. The 23 rd chromosome determines a person’s gender, or sex. Males are X and Y Females are X and X

16. A Karyotype

17. Gametes Gametes (or sex cells) are different in males and females. Male gametes have an XY. – During meiosis, a sperm cell can carry and X or Y. Female gametes have an XX – During meiosis, an egg cell can carry only an X. Males will determine the sex of a their offspring

18. Gender of Offspring The gender of the offspring is determined by the sperm cell – If they get an X or a Y XX – female XY – male The chances of someone being male or female is 50%, ALWAYS!

19. 3-9 What are sex-linked traits

20. Key Terms Sex-linked traits- Sex-linked traits- traits that are controlled by the sex chromosomes Carrier Carrier- an organism that has a recessive gene for a trait but does not show the trait (they are heterozygous) Pedigree Pedigree- chart that shows inheritance of certain traits over several generations.

21. Inherited traits Some traits are inherited along with gender. These traits are controlled by the X and Y gender chromosomes. Traits that are inherited along with gender are called sex linked traits. The X chromosome carries more traits than the Y. – So most of the sex-linked traits are found o the X chromosome.

22. Sex-linked Disorders Some hereditary disorders are caused by sex-linked traits. 2 examples are color blindness and hemophilia. – Hemophilia is when the blood does not clot properly. – Color blindness is where a person cannot see the different between colors.

23. Sex-linked disorders They are found more commonly in men than women. This is because the genes for most sex- linked disorders are recessive.

24. Carriers carriers Women who have one normal gene and one recessive gene (heterozygous) are said to be carriers of the disorder. – This means they carry the disorder and can pass it on, but do not have it themselves.

25. If we did a Punnett Square… Normal XX Carrier XX C Normal XY Color blind X C Y X X XCXCXCXC Y

26. Practice Problem #1 Dave is color blind, his wife Anna isn’t color blind, but her father is. What is the chances that they will have a color blind son? Dave is color blind, his wife Anna isn’t color blind, but her father is. What is the chances that they will have a color blind son?

27. Practice Problem #2 Susan is a carrier for color-blindness, her husband, Alex, isn’t color blind. What is the chance that they will have a color blind son? A daughter that is a carrier? Susan is a carrier for color-blindness, her husband, Alex, isn’t color blind. What is the chance that they will have a color blind son? A daughter that is a carrier?

28. Pedigrees Scientists often study the traits of past generations in order to predict the traits of offspring. One way to do this is to use a pedigree. Pedigrees are very similar to a family tree. It shows how a trait is passed from one generation to the next. Pedigrees can identify carriers of a trait, and people who have a trait.

29. How to read a pedigree A pedigree uses symbols to represent males, females, carriers, those who are normal, and those who have the trait that we are examining. A pedigree uses symbols to represent males, females, carriers, those who are normal, and those who have the trait that we are examining. All this information will be found in a key. All this information will be found in a key. A male will be represented by a square A male will be represented by a square A female by a circle. A female by a circle. Those who are affected by the trait will have their circle or square filled in. Those who are affected by the trait will have their circle or square filled in. Those who carry it, will have half of it filled in. Those who carry it, will have half of it filled in. And those who are normal, or don’t have it all, will have an empty or not colored in circle. And those who are normal, or don’t have it all, will have an empty or not colored in circle.

30. Left handed- ness Key:

31. Another Example

32. 3-10 What are some inherited diseases?

33. Key Term Inherited disease- disease caused by an inherited gene

34. Inherited disease Sometimes a gene is defective or abnormal. The abnormal gene stops the body from working correctly and then causes a disease An abnormal gene can be passed from parents to their offspring. This is called an inherited disease

35. Examples of Inherited Diseases Sickle-cell anemia- a disease that affects the shape of red blood cells. They are shaped like a crescent moon. PKU (phenylketonuria)- people who have this disease cannot eat foods that are protein rich such as fish, milk and eggs. Tay-Sachs Disease- is a disease that affects those who are mostly of Jewish decent. It affects children at an early age by preventing them from breaking down fat. As a result fat gathers in the child’s brain and causes death at an early age.

36. Huntington’s Disease- This one is carried by a dominant gene and it affects males in their later 30’s to 40’s after they have already had children. It breaks down the ability to control your muscles, and results in death at an earlier age than normal.

37. People in Science Genetic Counselor – Are people who study family histories and interpret test results in order to predict the possible traits of offspring.

38. 3-11 How does the environment affect inherited traits?

39. Key Terms Mutations- change in a gene

40. Conditions in the environment Genes control many of your traits. – This is true for all living organisms However sometimes, other factors can affect traits. The environment affects the traits of living things in many different ways. – Ex.) Green plants need sunlight to live. If they don’t have the greatest sunlight they won’t grow as tall.

41. Environment and Traits An example of the environment affecting trait is the divi-divi tree that lives on the island of Aruba. It grows side ways because of the strong winds, NOT because of genetics.

42. Environment and Genes Plants that are grown in poor soil are small in size. They will produce only a few fruits. Adding nutrients to the soil changes the environment, which means that the plant can now grow taller and produce more fruit. In this example the genes are not changed or affected, only the appearance of the plant.

43. Genetic Mutations A mutation is a change in the genetic material of an organism. – This can be harmful if it decreases the ability of the organism to function properly. If the mutation occurs in the gametes, it can be passed on to the next generation. If it only affects the body cells, it will NOT be passed to the next generation. Mutations can affect a single gene, or an entire chromosome.

44. Causes of Mutations Mutations occur randomly in nature. However, they can be increased by factors in the environment. Factors that increase mutations are called mutagens. – Ex.) ultraviolet light and some chemicals; radiation from X-rays or nuclear power plants. Some mutagens are known to cause cancer and are called carcinogens.

45. 3-12 How is genetics used to improve things?

46. Key Terms Controlled breeding- mating organisms to produce offspring with certain traits Mass selection- crossing plants with desirable traits Hybridization- mating two different kinds of organisms Inbreeding- mating closely related organisms.

47. Controlled breeding People have been raising and breeding crops and animals for thousands of years. Over the centuries they have learned that some crops produced better plants than others, and that some animals had better traits than others. They began to mate those with desirable traits together, this is called controlled breeding.

48. Mass selection Plant growers use a process called mass selection. – This is where plants with desirable traits are crossed. – Seeds from these plants are collected and then planted. – The seeds from those offspring with the desirable traits are then kept to keep the process going. An example of this is the corn that we eat.

49. Hybridization Sometimes 2 organisms with different kinds of genes are crossed. The offspring with show traits from both parents and is called a hybrid. The process of breeding 2 different organisms with different genes is called hybridization. – Ex.) mule- mother is a horse, father is a donkey.

50. Inbreeding Inbreeding is the mating of closely related organisms. The offspring have genes that are very similar to BOTH parents. This is done with racehorses, and a lot of plants.