1. PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE TAYLOR SIMON DICKEY HOGAN Chapter 8 Lecture by Edward J. Zalisko The Cellular Basis of Reproduction and Inheritance © 2015 Pearson Education, Inc.

2. A LTERATIONS OF C HROMOSOME N UMBER AND S TRUCTURE A LTERATIONS OF C HROMOSOME N UMBER AND S TRUCTURE

3. 8.18 Accidents during meiosis can alter chromosome number Nondisjunction is the failure of chromosomes or chromatids to separate normally during meiosis. This can happen during meiosis I, if both members of a homologous pair go to one pole, or meiosis II, if both sister chromatids go to one pole. Fertilization after nondisjunction yields zygotes with altered numbers of chromosomes. © 2015 Pearson Education, Inc.

4. Figure 8.18-1-1 Nondisjunction Meiosis I

5. © 2015 Pearson Education, Inc. Figure 8.18-1-2 Nondisjunction Normal meiosis II Meiosis II Meiosis I

6. © 2015 Pearson Education, Inc. Figure 8.18-1-3 Nondisjunction Normal meiosis II Gametes Number of chromosomes Abnormal gametes n + 1 n − 1 Meiosis II Meiosis I

7. © 2015 Pearson Education, Inc. Figure 8.18-2-2 Nondisjunction Normal meiosis I Meiosis II Meiosis I

8. © 2015 Pearson Education, Inc. Figure 8.18-2-3 Nondisjunction Normal meiosis I Meiosis II Meiosis I Abnormal gametes n + 1n − 1 Normal gametes n n

9. 8.19 A karyotype is a photographic inventory of an individual’s chromosomes A karyotype is an ordered display of magnified images of an individual’s chromosomes arranged in pairs. © 2015 Pearson Education, Inc.

10. Figure 8.19-3 Centromere Sister chromatids Pair of homologous chromosomes Sex chromosomes

11. 8.20 CONNECTION: An extra copy of chromosome 21 causes Down syndrome Trisomy 21 involves the inheritance of three copies of chromosome 21 and is the most common human chromosome abnormality. © 2015 Pearson Education, Inc.

12. 8.20 CONNECTION: An extra copy of chromosome 21 causes Down syndrome A person with trisomy 21 has a condition called Down syndrome, which produces a characteristic set of symptoms, including characteristic facial features, short stature, heart defects, susceptibility to respiratory infections, leukemia, and Alzheimer’s disease, and varying degrees of developmental disabilities. The incidence increases with the age of the mother. © 2015 Pearson Education, Inc.

13. Figure 8.20b Age of mother Infants with Down syndrome (per 1,000 births) 90 80 70 60 50 40 30 20 10 0 202530354045

14. © 2015 Pearson Education, Inc. Figure 8.20a-0 A person with Down syndrome Trisomy 21

15. 8.21 CONNECTION: Abnormal numbers of sex chromosomes do not usually affect survival Sex chromosome abnormalities seem to upset the genetic balance less than an unusual number of autosomes. This may be because of the small size of the Y chromosome or X chromosome inactivation. © 2015 Pearson Education, Inc.

16. 8.21 CONNECTION: Abnormal numbers of sex chromosomes do not usually affect survival The following table lists the most common human sex chromosome abnormalities. In general, a single Y chromosome is enough to produce “maleness,” even in combination with several X chromosomes, and the absence of a Y chromosome yields “femaleness.” © 2015 Pearson Education, Inc.

17. Table 8.21

18. 8.23 CONNECTION: Alterations of chromosome structure can cause birth defects and cancer Chromosome breakage can lead to rearrangements that can produce genetic disorders or, if changes occur in somatic cells, cancer. © 2015 Pearson Education, Inc.

19. 8.23 CONNECTION: Alterations of chromosome structure can cause birth defects and cancer These rearrangements can lead to four types of changes in chromosome structure. 1.A deletion is the loss of a chromosome segment. 2.A duplication is the repeat of a chromosome segment. 3.An inversion is the reversal of a chromosome segment. 4.A translocation is the attachment of a segment to a nonhomologous chromosome. A translocation may be reciprocal. © 2015 Pearson Education, Inc.

20. Figure 8.23a-0 Deletion Inversion DuplicationReciprocal translocation Homologous chromosomes Nonhomologous chromosomes

21. © 2015 Pearson Education, Inc. Figure 8.0-0

22. © 2015 Pearson Education, Inc. Figure 8.UN01 Genetically identical daughter cells Cytokinesis (division of the cytoplasm) Mitosis (division of the nucleus) G1G1 Cytokinesis Mitosis G2G2 M (DNA synthesis) S

23. © 2015 Pearson Education, Inc. 2n2n n n Figure 8.UN02 Sperm cell Egg cell Haploid gametes (n = 23) Human life cycle Multicellular diploid adults (2n = 46) Diploid zygote (2n = 46) n Meiosis n Fertilization Mitosis 2n2n

24. © 2015 Pearson Education, Inc. S EX C HROMOSOMES AND S EX -L INKED G ENES

25. © 2015 Pearson Education, Inc. 9.20 Chromosomes determine sex in many species Many animals have a pair of sex chromosomes, designated X and Y, that determine an individual’s sex. Among humans and other mammals, –individuals with one X chromosome and one Y chromosome are males, and –XX individuals are females. In addition, human males and females both have 44 autosomes (nonsex chromosomes). © 2015 Pearson Education, Inc.

26. 9.20 Chromosomes determine sex in many species In mammals (including humans), –the Y chromosome has a crucial gene, SRY, for the development of testes, and –an absence of the SRY gene directs ovaries to develop. © 2015 Pearson Education, Inc.

27. Figure 9.20a X Y

28. © 2015 Pearson Education, Inc. Figure 9.20b-0 Parents (diploid) Gametes (haploid) Offspring (diploid) MaleFemale Sperm Egg MaleFemale 44 + XY 44 + XX 44 + XY 44 + XX 22 + X 22 + Y 22 + X

29. © 2015 Pearson Education, Inc. 9.20 Chromosomes determine sex in many species Grasshoppers, roaches, and some other insects have an X-O system, in which –O stands for the absence of a sex chromosome, –females are XX, and –males are XO. In certain fishes, butterflies, and birds, –the sex chromosomes are Z and W, –males are ZZ, and –females are ZW. © 2015 Pearson Education, Inc.

30. 9.20 Chromosomes determine sex in many species Some organisms lack sex chromosomes altogether. In most ants and bees, sex is determined by chromosome number. –Females develop from fertilized eggs and thus are diploid. –Males develop from unfertilized eggs. Males are thus fatherless and haploid. © 2015 Pearson Education, Inc.

31. Table 9.20-0

32. © 2015 Pearson Education, Inc. 9.20 Chromosomes determine sex in many species In some animals, environmental temperature determines the sex. –For some species of reptiles, the temperature at which the eggs are incubated during a specific period of embryonic development determines whether the embryo will develop into a male or female. –Global climate change may therefore impact the sex ratio of such species. © 2015 Pearson Education, Inc.

33. 9.21 Sex-linked genes exhibit a unique pattern of inheritance Sex-linked genes are located on either of the sex chromosomes. The X chromosome carries many genes unrelated to sex. The inheritance of white eye color in the fruit fly illustrates an X-linked recessive trait. © 2015 Pearson Education, Inc.

34. Figure 9.21a-0

35. © 2015 Pearson Education, Inc. Figure 9.21a-1

36. © 2015 Pearson Education, Inc. Figure 9.21a-2

37. © 2015 Pearson Education, Inc. H UMAN D EVELOPMENT

38. © 2015 Pearson Education, Inc. 27.15 The embryo and placenta take shape during the first month of pregnancy Pregnancy, or gestation, is the carrying of developing young within the female reproductive tract. Human pregnancy averages 266 days (38 weeks) from fertilization (also called conception in humans), or 40 weeks (9 months) from the start of the last menstrual period.

39. © 2015 Pearson Education, Inc. 27.15 The embryo and placenta take shape during the first month of pregnancy Human development begins with fertilization in the oviduct when a single sperm is allowed to fuse with and by an egg. The single cell egg now has DNA from both parents. –Before fertilization, the egg and sperm were haploid, n. Each cell had one copy of each of the 23 chromosomes. –After fertilization, the egg is diploid, 2n, and it has two copies of each chromosome.

40. © 2015 Pearson Education, Inc. 27.15 The embryo and placenta take shape during the first month of pregnancy Cleavage (dividing) of the egg by mitosis produces a blastocyst –the inner cell mass becomes the embryo and –the trophoblast, the outer cell layer, attaches to the uterine wall and forms part of the placenta. Gastrulation occurs and organs develop from the three embryonic layers.

41. © 2015 Pearson Education, Inc. Figure 27.15ab Trophoblast Cavity Uterine cavity Blastocyst Cleavage starts Fertilization of mature egg by sperm Oviduct Secondary oocyte Ovulation Ovary Blastocyst (implanted) Endometrium Uterus Uterine cavity Inner cell mass

42. © 2015 Pearson Education, Inc. Figure 27.15c Endometrium Uterine cavity Trophoblast Multiplying cells of trophoblast (contribute to future placenta) Embryo Future yolk sac Blood vessel (maternal)