1. Heredity Chapter 4

2. Standard: S7L3 Students will recognize how biological traits are passed on to successive generations.  a. Explain the role of genes and chromosomes in the process of inheriting a specific trait.

3. Heredity The passing of traits from parents to offspring. Traits- The characteristics of an organism.

4. Alleles A different form of a gene. One allele may code for dimples, and the other for no dimples.

5. Parents You get one allele from mom, and one from dad.

6. Genetics The study of how traits are inherited through the interactions of alleles.

7. Gregor Mendel The first to study how traits were passed from one generation to the next. He studied pea plants.

8. Mendel’s Experiments Mendel crossed a pure breeding white flowered plant with a pure breeding purple flowered plant He got all purple flowers BUT, then he crossed two of the second generation purples and he got ¾ purple and ¼ white!

9. What does that mean? Mendel decided that meant that one alleles was dominant and the other allele was recessive

10. Dominant vs. Recessive Dominant Alleles- An allele that covers, or dominates another allele. Recessive Allele- An allele that is covered, or hidden by another allele.

15. Punnett Squares A tool to predict the probability of certain traits in offspring. Punnett squares show the different ways alleles can combine.

16. Representing Alleles Letters! Upper case= dominant alleles. (R) Lower case =recessive alleles. (r)

17. Homozygous If the two alleles that you get from mom & dad are the same, it is homozygous(RR, rr)

18. Heterozygous An organism that has two different alleles for a trait is called heterozygous. (Rr)

19. Genotype vs. Phenotype Genotype- An organism’s genetic makeup. Phenotype- Outward appearance, or behavior of an organism.

20. Example The tongue rolling allele is R. R is dominant r is recessive

21. Your mom is homozygous dominant for the tongue rolling gene. Her genotype is RR

22. Your dad is heterozygous for the tongue rolling gene. His genotype is Rr

23. Probability What is the probability that you will be able to roll your tongue? Do a Punnett Square!

24. Making a Punnett Square To set up a Punnett Square, draw a large square, and then divide it into four equal sections.

25. Dad’s Alleles go on top Mom’s Alleles go on the side

26. R R R r Eggs Sperm

27. RRRrRr RrRr R R R r Eggs Sperm

28. Your genotype could be: 50% RR- Homozygous Dominant 50% Rr- Heterozygous Your phenotype would be: 100% Tongue Roller 0% No Tongue Roller

29. Hybrid vs. Purebred Hybrids=Heterozygous- Have two different alleles for a gene: Rr Purebreds=Homozygous- Have the same allele for a gene: RR or rr

30. Let’s Do Another One! The Big Nose Allele is N. Big Nose is N Little nose is n

31. Mom is Heterozygous for Big Nose: Nn Dad is Heterozygous for Big Nose: Nn What is the chance you’ll have a big nose? Do the cross!

32. NNNnNn nnNnNn N N n n Eggs Sperm

33. What is the genotype? 25% NN- Homozygous Dominant 50% Nn- Heterozygous 25% nn- Homozygous Recessive

34. What is the phenotype? 75% Big Nose 25% little nose

35. Incomplete Dominance When the offspring of two homozygous parents show an “in-between” phenotype.

36. Example Purebred white flowers Purebred red flowers Makes “in-between” color pink flowers

37. Multiple Alleles Any trait that is controlled by many alleles. Blood type is an example.

39. Polygenic Inheritance When many genes act to control a trait. Examples include hair, eye and skin color

43. Chromosome Disorders If a sperm or egg cell gets fewer or more chromosomes than normal, this can cause genetic disease.

44. Down’s Syndrome These persons have three copies of chromosome #21. They can be shorter, have learning disabilities and heart problems.

45. DDDD_D_ D_D_ DD D D ? Eggs Sperm Down’s Syndrome Fetus Dies

46. Non-disjunction When chromosomes fail to separate. One sex cell gets an extra chromosome. One sex cell doesn’t get a chromosome.

48. Recessive Genetic Disorders Offspring only gets the disease if he/she inherits the recessive alleles from mom and dad.

49. Cystic Fibrosis Causes a thick fluid to build up in the lungs, making it difficult to breathe. Cystic Fibrosis is a Recessive Genetic Disorder.

50. Carriers Mom and dad are carriers- They carry the defective allele, but don’t have the disease.

52. CCCcCc ccCcCc C C c c Eggs Sperm Cystic Fibrosis

53. Sex Determination Females have XX chromosomes. Males have XY chromosomes.

54. XXXYXY XYXY X X X Y Eggs Sperm Girls Boys

55. Sex-Linked Disorders An allele inherited on a sex chromosome. Color blindness is an example.

56. Selective Breeding Selecting plants or animals with the most desirable traits to breed for the next generation.

60. Genetic Engineering Finding desirable genes in one plant, and inserting them into another plant. This can make vegetables bigger, heartier and more resistant to insects and fungi.

64. Genetic Anomalies