1. Chromosomes and Inheritance 5 Lecture Presentation by Wendy Kuntz Chapter © 2015 Pearson Education, Inc.

2. Chapter 5 Chromosomes and Inheritance: Unit Hyperlinks 5.1 Cell division 5.2 What is DNA? 5.3 Cell cycle? 5.4 Mitosis 5.5 Cytokinesis 5.6 Gametes 5.7 Meiosis 5.8 Mitosis vs. meiosis 5.9 Genetic variation

3. © 2015 Pearson Education, Inc. Chapter 5 Chromosomes and Inheritance: Unit Hyperlinks 5.10 Meiosis mistakes 5.11 Mendelian genetics 5.12 Punnett square 5.13 Independent assortment 5.14 Pedigrees 5.15 Complex inheritance 5.16 Linked genes 5.17 Sex-linked genes 5.18 Clones

4. © 2015 Pearson Education, Inc. 5.1 Opening Questions: Cell birth and death Is your body making any new cells right now? What kind? Are certain types of cells replaced faster? What might be examples? Are certain types of cells never replaced or slowly replaced? What might be examples? Did you know that between 50 and 70 billion of your cells die each day?

5. © 2015 Pearson Education, Inc. 5.1 All living organisms consist of cells. A fundamental concept in biology is the cell theory, which states: 1.All life is cellular. 2.All cells arise from preexisting cells. Some living organisms have just one cell, but others have trillions.

6. © 2015 Pearson Education, Inc. 5.1 Cell division is the formation of new cells from preexisting cells Cell division provides for 1.Growth 2.Repair 3.Reproduction Organisms can use cell division to reproduce sexually or asexually.

7. © 2015 Pearson Education, Inc. 5.1 Sexual reproduction takes two parents Two parents produce genetically unique offspring. Gametes (egg and sperm cells) are formed via cell division from adult cells in the gonads (testes and ovaries).

8. © 2015 Pearson Education, Inc. 5.1 Life cycle in sexual reproduction:

9. © 2015 Pearson Education, Inc. 5.1 Asexual reproduction only needs one parent One parent produces genetically identical offspring. There is no sperm or egg involved.

10. © 2015 Pearson Education, Inc. 5.1 Sexual vs. asexual reproduction Complete the comparison table: SexualAsexual Number of parents needed Gametes? (yes/no) Fertilization? (yes/no) Number of chromosome sets Offspring genetically unique? (yes/no)

11. © 2015 Pearson Education, Inc. 5.1 Sexual vs. asexual reproduction SexualAsexual Number of parents needed 21 Gametes? (yes/no) YESNO Fertilization? (yes/no) YESNO Number of chromosome sets 21 Offspring genetically unique? (yes/no) YESNO

12. © 2015 Pearson Education, Inc. 5.2 Opening Questions: What is DNA? What type of information is stored in DNA? How different is your DNA from the person sitting next to you?

13. © 2015 Pearson Education, Inc. What type of information is stored in DNA? How different is your DNA from the person sitting next to you? 5.2 Opening Questions: What is DNA?

14. © 2015 Pearson Education, Inc. 5.2 DNA and genes: All life on Earth uses DNA as the genetic material. The nucleus of every eukaryotic cell contains long strands of DNA called chromosomes. Each chromosome contains genetic information in genes.

15. © 2015 Pearson Education, Inc. 5.2 DNA and genes: A gene is a length of DNA that codes for the proteins that make up our bodies. Genes are the unit of inheritance.

16. © 2015 Pearson Education, Inc. 450x11,000x550,000x 5.2 A closer look at the chromosome Inside the nucleus, the chromosomal DNA is wound around proteins; together they form chromatin. Most of the time chromosomes are unraveled as loose chromatin.

17. © 2015 Pearson Education, Inc. 5.2 Chromosome number: every human body cell has 46 chromosomes How many chromosomes did you inherit from your mother?

18. © 2015 Pearson Education, Inc. At cell division chromosomes 1.Become tightly packed 2.Duplicate Pairs of duplicated chromosomes are called sister chromatids. 5.2 Chromosomes at cell division have unique properties

19. © 2015 Pearson Education, Inc. 5.2 Chromosomes duplicate prior to division Sister chromatids (duplicated chromosome pair) are joined at the centromere. Formation of sister chromatids means the cell is preparing to divide.

20. © 2015 Pearson Education, Inc. 5.3 Opening Questions: Cell cycle Healthy cells only start dividing if there is a need for replication. Provide at least three examples of times when a cell (animal, plant, protist) would need to go through cell division.

21. © 2015 Pearson Education, Inc. 5.3 Opening Questions: Cell cycle Unhealthy cells may undergo unregulated cell division. Cancer begins when a cell divides although it should not. What are some things you know about cancer? Why might cancer be so difficult to treat?

22. © 2015 Pearson Education, Inc. 5.3 Cells have regular cycles of growth and division The cell cycle is an ordered sequence of events in the “lifetime” of a cell. There are two broad phases: 1. Interphase 90% of cell’s lifetime Normal cell functions 2. Mitotic phase Active cell division

23. © 2015 Pearson Education, Inc. 5.3 The cell cycle: Healthy cells only enter the mitotic phase if duplication is needed.

24. © 2015 Pearson Education, Inc. During interphase, the cell Performs its normal functions Grows Prepares for division by duplicating its chromosomes 5.3 Most of a cell’s lifetime is spent in interphase What are some normal functions of cells?

25. © 2015 Pearson Education, Inc. 5.3 Active cell division is the mitotic phase During the mitotic phase, the cell Undergoes active division (mitosis) Splits into two offspring cells (cytokinesis) The result of the mitotic phase is two genetically identical offspring cells.

26. © 2015 Pearson Education, Inc. 5.4 Opening Questions: Mitosis puzzle ABCD The cells below are all undergoing the process of cell division. Think about what is happening in the cell during division, and try putting them in logical order from start to finish. Explain your choices.

27. © 2015 Pearson Education, Inc. 5.4 Mitosis is active cell division Mitosis occurs in major stages. These stages help us think about how the chromosomes are organized during mitosis. However, cell division proceeds seamlessly through all the stages.

28. © 2015 Pearson Education, Inc. 5.4 Interphase: 1.Early interphase Cell is carrying out its normal activities. 2.Chromosomes duplicate Cell is preparing to divide; generates sister chromatids.

29. © 2015 Pearson Education, Inc. 5.4 Stages of mitosis 3.Chromosomes condense Nuclear membrane dissolves. Cell lays down mitotic spindle. 4.Chromosomes align Sister chromatids line up and attach to mitotic spindle.

30. © 2015 Pearson Education, Inc. 5.4 Stages of mitosis 5.Chromosomes split Sister chromatids are pulled apart as mitotic spindle retracts. 6.Nucleus reforms Two duplicated nuclei are formed.

31. © 2015 Pearson Education, Inc. 5.5 Cytokinesis is the final step in cell division Cytokinesis is the division of the cytoplasm and is the final step in the cell cycle. The process of cytokinesis is different for plant and animal cells

32. © 2015 Pearson Education, Inc. 5.5 Cytokinesis in animal cells: The parent animal cell is pinched into two, leaving two independent offspring cells.

33. © 2015 Pearson Education, Inc. 5.5 Cytokinesis in plant cells: Plant cells divide their cytoplasm by forming a cell plate along the center line of the cell.

34. © 2015 Pearson Education, Inc. 5.5 Review Questions: What side effects have you heard of related to chemotherapy treatment for cancer? With your understanding of mitosis, can you explain some of the side effects of chemotherapy? Many chemotherapy drugs are used to treat cancer by killing cells undergoing mitosis.

35. © 2015 Pearson Education, Inc. 5.6 Opening Questions: How do you get one from two? Most of the cells in your body are diploid; they have two copies of each chromosome. If your cells are diploid, how could you reproduce without doubling the chromosome number in your offspring?

36. © 2015 Pearson Education, Inc. 5.6 Gametes are the answer! To prevent doubling chromosome number in offspring, sexually reproducing organisms need to make cells with a single set of chromosomes. Gametes, or sex cells, are haploid: they contain only one copy of each chromosome.

37. © 2015 Pearson Education, Inc. 5.6 Male and female gametes: Male gametes are called sperm. Female gametes are called eggs. How many chromosomes are there in a human sperm cell?

38. © 2015 Pearson Education, Inc. 5.6 The human life cycle: DEVELOPMENT Through repeated rounds of cell division, the original zygote cell is duplicated, eventually forming an embryo, then a baby, and finally an adult. ZYGOTE The zygote, or fertilized egg, is the original cell that was formed by the fusion of sperm and egg. The zygote contains one haploid set of chromo- somes from the father and one haploid set of chromo- somes from the mother that together make a unique diploid set of chromosomes. During fertilization, the gametes (male sperm and female egg) fuse. Each contributes a haploid number of chromosomes to produce a diploid zygote. GAMETE FORMATION In the adult gonads (testes in males and ovaries in females), a special kind of cell division produces gametes. The male gamete is the sperm and the female gamete is the egg. As the only haploid cells in your body, gametes can be used to form the next generation. ADULTS Every somatic cell in your body is diploid, with one set of chromosomes derived from your mother and one from your father.

39. © 2015 Pearson Education, Inc. 5.6 One pair of chromosomes makes you male or female The 46 chromosomes in your body are organized as 23 homologous pairs. Of these, 22 pairs are autosomes. One pair is your sex chromosomes. –Females are XX. –Males are XY.

40. © 2015 Pearson Education, Inc. 5.6 Karyotypes are photographic inventories of chromosomes Chromosomes are organized in homologous pairs. Can you tell if this a male or a female?

41. © 2015 Pearson Education, Inc. 5.7 Opening Questions: Why do we need to produce sperm and eggs (gametes)? Explain why all sexually reproducing organisms need both haploid and diploid cells. Remember: Haploid cells have only one copy of each chromosome. Diploid cells have two copies of each chromosome.

42. © 2015 Pearson Education, Inc. 5.7 Meiosis is the production of gametes Gametes (sperm and egg) are formed by a special type of cell division, meiosis. Cells produced from meiosis are haploid. Like mitosis, meiosis occurs in stages.

43. © 2015 Pearson Education, Inc. 5.7 Meiosis occurs in stages Meiosis (like mitosis) starts with chromosome duplication before division. In meiosis, there are then two rounds of cell division. The result of meiosis is four haploid offspring cells, all with one-half the number of chromosomes.

44. © 2015 Pearson Education, Inc. 5.7 Meiosis interphase Remember that chromosomes come in homologous (matched) pairs. In meiosis interphase, chromosomes duplicate. After interphase, cells that are producing gametes undergo two rounds of division called meiosis I and meiosis II.

45. © 2015 Pearson Education, Inc. 5.7 Meiosis I: 1.Homologous chromosome pairs line up 2.Homologous pairs separate 3.Cytokinesis Note that in meiosis I the homologous pairs line up and separate.

46. © 2015 Pearson Education, Inc. 5.7 Stages of meiosis II: 4.Chromosomes condense and line up 5.Chromosomes separate 6.Cytokinesis II At the end of meiosis II there are four haploid offspring cells.

47. © 2015 Pearson Education, Inc. 5.8 Opening Questions: Meiosis vs. mitosis MeiosisMitosis Where does it occur? When is it needed? How many/type offspring cells? (haploid/diploid) How many rounds of cell divisions? Try to complete the comparison table below:

48. © 2015 Pearson Education, Inc. 5.8 Mitosis and meiosis compared MeiosisMitosis Where does it occur? Ovaries/ testes All body cells When is it needed? PubertyLifetime How many/type offspring cells? (haploid/diploid) 4 haploid2 diploid How many rounds of cell divisions? 21

49. © 2015 Pearson Education, Inc. 5.8 Study aids: Come up with some study aids to help you remember when the body needs to use meiosis versus mitosis.

50. © 2015 Pearson Education, Inc. 5.9 Opening Questions: How unique are you? What is the probability that another human on earth shares the exact same DNA as you?

51. © 2015 Pearson Education, Inc. 5.9 Opening Questions: How unique are you? What is the probability that another human on earth shares the exact same DNA as you? Unless you have an identical twin, you are genetically different from any human that has every lived! How is that possible?!

52. © 2015 Pearson Education, Inc. 5.9 Sexual reproduction leads to variation Three major processes mean variation is the norm for sexual reproduction: 1. Independent assortment 2. Random fertilization 3. Crossing over

53. © 2015 Pearson Education, Inc. 5.9 Independent assortment of chromosomes leads to variation Chromosomes line up by homologous pairs during meiosis I. Maternal and paternal chromosomes are shuffled randomly. Independent assortment: 2 23 = 8 million possible arrangements of chromosomes! Chromosomes are shuffled

54. © 2015 Pearson Education, Inc. 5.9 Random fertilization by sperm and egg leads to variation The probability that any one sperm will fertilize any particular egg is extremely small. Random fertilization: 8 million x 8 million = 64 trillion possible arrangements of chromosomes. Chromosomes are shuffled

55. © 2015 Pearson Education, Inc. 5.9 Crossing over during meiosis leads to variation Chromosomes can “swap” genetic material, creating new, unique combinations. Crossing over occurs when homologous chromosomes line up during meiosis I. Crossing over creates new hybrid chromosomes, which increases gene variation.

56. © 2015 Pearson Education, Inc. 5.10 Opening Questions: What if meiosis goes wrong? Jason and Laura are pregnant with their third child. Since they are both over 35, they opt to have an amniocentesis test. The doctor comes back to them with a karyotype that shows 47 chromosomes. Imagine you are Jason and Laura’s genetic counselor. How would you explain the results?

57. © 2015 Pearson Education, Inc. 5.10 Meiosis can have mishaps! Non-disjunction is when chromosomes fail to separate properly. Resulting gametes will have too few or too many chromosomes. Zygotes with abnormal chromosome number will usually not develop or will have abnormalities.

58. © 2015 Pearson Education, Inc. 5.10 Examples of nondisjunction Trisomy 21 is a condition in which a person receives three copies of chromosome 21. The resulting condition is called Down syndrome.

59. © 2015 Pearson Education, Inc. 5.10 Examples of nondisjunction Sex chromosome nondisjunction can also occur. Each combination of extra or missing sex chromosomes produces its own syndromes.

60. © 2015 Pearson Education, Inc. 5.10 Examples of nondisjunction

61. © 2015 Pearson Education, Inc. 5.11 Opening Questions: Did you inherit your good looks? Why do children resemble their parents? Why do families resemble each other? Is there anything you can’t inherit from your parents?

62. © 2015 Pearson Education, Inc. 5.11 Our understanding of genetics starts with Mendel Heredity is the transmission of traits from one generation to the next. Genetics is the study of heredity. Gregor Mendel was the first to deduce the basic principles of inheritance.

63. © 2015 Pearson Education, Inc. 5.11 Character and traits are inherited Human eye color is a character, or an inherited feature that varies among individuals. Each possible variation of a character is a trait.

64. © 2015 Pearson Education, Inc. 5.11 Alleles are the individual units of inheritance Traits derive from genes. Alternate forms of a particular gene are called alleles. Matched set of chromosomes, one derived from the father (blue) and one derived from the mother (red)

65. © 2015 Pearson Education, Inc. 5.11 Genotype vs. phenotype An organism’s phenotype is its physical traits. An organism’s genotype is its underlying genetic make-up, the alleles it is carrying.

66. © 2015 Pearson Education, Inc. 5.11 Dominant vs. recessive alleles An individual who is heterozygous has two different alleles. Only one allele will usually determine an organism’s appearance. In pea plants, purple (P) is the dominant trait for flower color. White (p) is the recessive trait.

67. © 2015 Pearson Education, Inc. 5.12 Opening Questions: Can we predict the inheritance patterns of genes? For some people the chemical PTC (phenylthiocarbamide) tastes very bitter; yet for others, it is tasteless. Scientists report that the ability to taste PTC shows a general pattern of dominant inheritance (T and t). What is the genotype of a non-taster? Could a non-taster’s parents be tasters?

68. © 2015 Pearson Education, Inc. 5.12 A Punnett square can be used to predict the results of a genetic cross In a genetic cross, two parents (P generation) are crossed to produce offspring (F1 generation). A Punnett square can be used to predict the offspring that will result from a genetic cross. ×

69. © 2015 Pearson Education, Inc. 5.12 Punnett squares are predictions Punnett squares are named after a British geneticist: Reginald Punnett. A Punnett square allows you to predict the genotype and phenotype of the offspring. The simplest Punnett square follows one character in a monohybrid cross.

70. © 2015 Pearson Education, Inc. 5.12 Punnett square: Monohybrid cross

71. © 2015 Pearson Education, Inc. 5.12 Alleles separate during meiosis The law of segregation states that the two alleles for a character separate during gamete formation.

72. © 2015 Pearson Education, Inc. 5.12 We can use a test cross to determine an individual’s genotype × For the test cross above, predict offspring ratios for each possible genotype. Is the genotype of this black Lab BB or Bb ? To find out, mate it with a chocolate Lab. Chocolate Lab with genotype bb

73. © 2015 Pearson Education, Inc. 5.12 Test cross results if black dog is BB:

74. © 2015 Pearson Education, Inc. 5.12 Test cross results if black dog is Bb:

75. © 2015 Pearson Education, Inc. 5.13 Opening Questions: Can we look at more than one trait? In Labrador retrievers, breeders need to keep track of traits for coat color (black is dominant to chocolate) and hearing (normal is dominant to deafness). If you want all chocolate coats, how would you avoid breeding deaf puppies?

76. © 2015 Pearson Education, Inc. 5.13 Alleles separate independently during gamete formation The law of independent assortment states that the inheritance of one character has no effect on the inheritance of another.

77. © 2015 Pearson Education, Inc. 5.13 Traits for coat color and hearing are an example of independent assortment All four kinds of gametes are equally likely to be produced. Genotype: BbDd Phenotype: black coat, hearing

78. © 2015 Pearson Education, Inc. 5.13 Independent assortment can be observed during a dihybrid cross MALE Phenotype: black coat hearing Genotype: BbDd × What are the possible allele combinations for the gametes? A dihybrid cross is one in which two separate characters are studied. FEMALE Phenotype: black coat hearing Genotype: BbDd

79. © 2015 Pearson Education, Inc. 5.13 Dihybrid cross:

80. © 2015 Pearson Education, Inc. 5.14 Opening Questions: Can understanding inheritance help us understand disease? Katie and Dave are a healthy young couple, but both have a sibling with cystic fibrosis (a recessive disorder). Genetic tests reveal they are both heterozygous. They want to know their risk of having a child with cystic fibrosis. If you were their genetic counselor, how would you explain the risks?

81. © 2015 Pearson Education, Inc. 5.14 Some human genetic characters are controlled by one gene For example, the freckled phenotype is dominant to the non-freckled phenotype.

82. © 2015 Pearson Education, Inc. 5.14 Many human genetic disorders are recessive A carrier is a heterozygous individual. Carriers do not have the disease, but they can pass it on to offspring.

83. © 2015 Pearson Education, Inc. 5.14 Pedigrees can be used to track genetic traits in a family This daughter does not have the trait, but we cannot tell if she is Aa or AA. This daughter has the trait and therefore must be aa, having inherited the recessive allele from each parent. Because this man has a daughter with the trait but does not have the trait himself, he must be a carrier. This child has the trait, which is how we know her father was a carrier (she could not have inherited two recessive alleles from her mother.) These three children must have received one a recessive allele from their affected mother, but they don’t have the trait. So they must be carriers themselves. Because they produced a daughter with the trait but don’t have it themselves, both grandparents must be carriers. Grandma and grandpa had two daughters, one of whom married and had four kids.

84. © 2015 Pearson Education, Inc. 5.15 Opening Questions: Can we always count on Mendel’s laws? Farmers have long observed that crossing cattle with red and white coats results in offspring with a roan color (intermediate color). If coat color is a single gene with two alleles (R and r), does the roan color make sense according to Mendel’s laws? If not, how would you explain it?

85. © 2015 Pearson Education, Inc. 5.15 Genetic inheritance has complexities Not all genes follow a classic Mendelian inheritance pattern. We often encounter patterns that are more complex.

86. © 2015 Pearson Education, Inc. 5.15 Sometimes both alleles are expressed For some genes there is a pattern of incomplete dominance. Individuals that are heterozygous will have a phenotype intermediate in appearance. Remember: in classic Mendelian genetics, heterozygous individuals have the appearance (phenotype) of the dominant gene.

87. © 2015 Pearson Education, Inc. 5.15 Flower color in snapdragons is a trait with incomplete dominance Heterozygous individuals show an intermediate trait. Now use a Punnett square to predict the outcome of Rr × Rr for snapdragons.

88. © 2015 Pearson Education, Inc. 5.15 A cross between two pink snapdragons exemplifies incomplete dominance Only RR individuals have a red phenotype.

89. © 2015 Pearson Education, Inc. © 20## Pearson Education, Inc. 5.15 For most traits there are multiple alleles Classic Mendelian genetics only uses two allele copies (such as R and r). Most genes actually have multiple alleles. For any gene, how many allele copies can one person carry?

90. © 2015 Pearson Education, Inc. 5.15 Blood types in humans are the result of multiple alleles Human blood types are determined by a gene with three alleles: i, I A, I B. These three alleles can be combined in six ways. Alleles for blood type are also codominant, which means both are expressed.

91. © 2015 Pearson Education, Inc. 5.15 Parents with different blood types exemplify multiple alleles and codominance

92. © 2015 Pearson Education, Inc. 5.15 Genes may have multiple effects In some cases, one gene influences many characters, a situation called pleiotropy. The sickle-cell mutation can cause many physical changes.

93. © 2015 Pearson Education, Inc. 5.15 Many phenotypic characters are the result of many genes Polygenic inheritance is the effect of many genes on a single character. In humans, height and skin color are each affected by several genes.

94. © 2015 Pearson Education, Inc. 5.15 Many genes have both a genetic and environmental component Some traits are entirely genetic, some are a mix of environment and genetics, and some traits are just environmental. Only genetic influences are inherited!

95. © 2015 Pearson Education, Inc. 5.16 Opening Questions: What if traits are on the same chromosome? So far, we have assumed that traits are on different chromosomes. But what if they are on the same chromosome? Will they still segregate independently?

96. © 2015 Pearson Education, Inc. 5.16 Not all genes obey Mendel’s law of independent assortment Linked genes are located close together on the same chromosome and tend to be inherited together. Linked genes display different offspring ratios compared to unlinked genes.

97. © 2015 Pearson Education, Inc. 5.16 Crossing over is less likely to occur for closely located genes Crossing over produces new hybrid recombinant chromosomes. Genes located very near each other have little chance of a crossover.

98. © 2015 Pearson Education, Inc. 5.17 Opening Questions: What if traits are on the sex chromosomes? So far, we have assumed that traits are on autosomes. But what if they are on the sex chromosome (X or Y)? How might patterns of inheritance differ? What if there is a genetic disease just on the X chromosome? What about phenotype?

99. © 2015 Pearson Education, Inc. 5.17 Sex-linked genes are those carried on the sex chromosomes Human cells contain 44 autosomes and 2 sex chromosomes: XX = Female XY = Male Because females have two X chromosomes while males have only one, sex-linked gene display unusual inheritance patterns.

100. © 2015 Pearson Education, Inc. 5.17 Hemophilia is a recessive mutation carried on the X chromosome A single copy of the normal (dominant) gene will prevent the disease. Men have a single X chromosome, so a male carrier of the hemophilia gene will have the disorder. In the last Russian royal family, the son had hemophilia, which he inherited from his mother.

101. © 2015 Pearson Education, Inc. 5.18 Opening Questions: Can science harness cell division? In 2004, a company called Genetic Savings & Clone produced the first commercially cloned pet, a cat named Little Nicky (for a fee of $50,000). Would you clone your pet? What are some other possible scientific uses of cloning?

102. © 2015 Pearson Education, Inc. 5.18 Nuclear transfer can be used to produce clones Biologists can artificially manipulate cell division to produce clones. –Clones are genetically identical individuals born of a single parent.

103. © 2015 Pearson Education, Inc. 5.18 Cloning can be done through the process of nuclear transplantation

104. © 2015 Pearson Education, Inc. 5.18 Cloned embryos can be used to produce a new individual In reproductive cloning the embryo must be transplanted into a surrogate.

105. © 2015 Pearson Education, Inc. 5.18 Cloned embryos can be used to produce stem cells In therapeutic cloning, stem cells are harvested from the cloned embryo.