Mitosis and the Cell Cycle

Interphase and the mitotic phase alternate in the Cell Cycle.

Cytokinesis

Meiosis

Figure 13.3 Preparing a karyotype APPLICATION TECHNIQUE 5 µm Pair of homologous replicated chromosomes Figure 13.3 Preparing a karyotype Centromere Sister chromatids Metaphase chromosome

chromatids in a homologous pair Pair of homologous chromosomes Fig. 13-4 Key Maternal set of chromosomes (n = 3) 2n = 6 Paternal set of chromosomes (n = 3) Two sister chromatids of one replicated chromosome Centromere Figure 13.4 Describing chromosomes Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set)

Multicellular diploid adults (2n = 46) Fig. 13-5 Key Haploid gametes (n = 23) Haploid (n) Egg (n) Diploid (2n) Sperm (n) MEIOSIS FERTILIZATION Ovary Testis Diploid zygote (2n = 46) Figure 13.5 The human life cycle Mitosis and development Multicellular diploid adults (2n = 46)

Key Haploid (n) Diploid (2n)) Gametes n n n MEIOSIS FERTILIZATION Fig. 13-6a Key Haploid (n) Diploid (2n)) Gametes n n n MEIOSIS FERTILIZATION Zygote Figure 13.6a Three types of sexual life cycles—animals 2n 2n Diploid multicellular organism Mitosis (a) Animals

(b) Plants and some algae Fig. 13-6b Key Haploid (n) Haploid multi- cellular organism (gametophyte) Diploid (2n) Mitosis Mitosis n n n n n Spores Gametes MEIOSIS FERTILIZATION Figure 13.6b Three types of sexual life cycles—plants and some algae 2n 2n Zygote Diploid multicellular organism (sporophyte)) Mitosis (b) Plants and some algae

Haploid unicellular or multicellular organism Diploid (2n) Fig. 13-6c Key Haploid (n) Haploid unicellular or multicellular organism Diploid (2n) Mitosis Mitosis n n n n Gametes n MEIOSIS FERTILIZATION Figure 13.6c Three types of sexual life cycles—most fungi and some protists 2n Zygote (c) Most fungi and some protists

Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Meiosis I Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number 1 Homologous schromosomes separate chromosome Haploid cells with replicated chromosomes Meiosis II 2 Sister chromatids separate Haploid cells with unreplicated chromosomes

Prophase I Metaphase I Anaphase I Centrosome (with centriole pair) Fig. 13-8a Telophase I and Cytokinesis Prophase I Metaphase I Anaphase I Centrosome (with centriole pair) Sister chromatids remain attached Centromere (with kinetochore) Sister chromatids Chiasmata Spindle Metaphase plate Figure 13.8 The meiotic division of an animal cell Cleavage furrow Homologous chromosomes Homologous chromosomes separate Fragments of nuclear envelope Microtubule attached to kinetochore

Figure 13.8 The meiotic division of an animal cell Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis Centrosome (with centriole pair) Sister chromatids remain attached Centromere (with kinetochore) Sister chromatids Chiasmata Spindle Metaphase plate Sister chromatids separate Haploid daughter cells forming Homologous chromosomes Homologous chromosomes separate Cleavage furrow Fragments of nuclear envelope Microtubule attached to kinetochore Figure 13.8 The meiotic division of an animal cell

Replicated chromosome Fig. 13-9a MITOSIS MEIOSIS MEIOSIS I Parent cell Chiasma Chromosome replication Chromosome replication Prophase Prophase I Homologous chromosome pair 2n = 6 Replicated chromosome Metaphase Metaphase I Anaphase Telophase Anaphase I Figure 13.9 A comparison of mitosis and meiosis in diploid cells Telophase II Haploid n = 3 Daughter cells of meiosis I 2n 2n MEIOSIS II Daughter cells of mitosis n n n n Daughter cells of meiosis II

Figure 13.9 A comparison of mitosis and meiosis in diploid cells Fig. 13-9b SUMMARY Property Mitosis Meiosis DNA replication Occurs during interphase before mitosis begins Occurs during interphase before meiosis I begins Number of divisions One, including prophase, metaphase, anaphase, and telophase Two, each including prophase, metaphase, anaphase, and telophase Synapsis of homologous chromosomes Does not occur Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion Number of daughter cells and genetic composition Two, each diploid (2n) and genetically identical to the parent cell Four, each haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other Figure 13.9 A comparison of mitosis and meiosis in diploid cells Role in the animal body Enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction Produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes

Possibility 1 Possibility 2 Two equally probable arrangements of Fig. 13-11-3 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Figure 13.11 The independent assortment of homologous chromosomes in meiosis Daughter cells Combination 1 Combination 2 Combination 3 Combination 4

Recombinant chromosomes Fig. 13-12-5 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Anaphase I Figure 13.12 The results of crossing over during meiosis Anaphase II Daughter cells Recombinant chromosomes

Mendelian Genetics

TECHNIQUE Parental generation (P) Stamens Carpel RESULTS First filial Fig. 14-2 TECHNIQUE 1 2 Parental generation (P) Stamens Carpel 3 4 Figure14.2 Crossing pea plants RESULTS First filial gener- ation offspring (F1) 5

EXPERIMENT P Generation (true-breeding parents) Purple flowers White Fig. 14-3-3 EXPERIMENT P Generation (true-breeding parents)  Purple flowers White flowers F1 Generation (hybrids) All plants had purple flowers Figure 14.3 When F1 hybrid pea plants are allowed to self-pollinate, which traits appear in the F2 generation? F2 Generation 224 white-flowered plants 705 purple-flowered plants

Table 14-1

Allele for purple flowers Fig. 14-4 Allele for purple flowers Homologous pair of chromosomes Locus for flower-color gene Figure 14.4 Alleles, alternative versions of a gene Allele for white flowers

P Generation Appearance: Purple flowers White flowers Genetic makeup: Fig. 14-5-3 P Generation Appearance: Purple flowers White flowers Genetic makeup: PP pp Gametes: P p F1 Generation Appearance: Purple flowers Genetic makeup: Pp Gametes: 1/2 P 1/2 p Sperm Figure 14.5 Mendel’s law of segregation F2 Generation P p P PP Pp Eggs p Pp pp 3 1

TECHNIQUE RESULTS Dominant phenotype, unknown genotype: PP or Pp? Fig. 14-7 TECHNIQUE  Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp Predictions If PP If Pp or Sperm Sperm p p p p P P Pp Pp Pp Pp Eggs Eggs Figure 14.7 The testcross P p Pp Pp pp pp RESULTS or All offspring purple 1/2 offspring purple and 1/2 offspring white

EXPERIMENT RESULTS Fig. 14-8 P Generation F1 Generation Hypothesis of YYRR yyrr Gametes YR  yr F1 Generation YyRr Hypothesis of dependent assortment Hypothesis of independent assortment Predictions Sperm or Predicted offspring of F2 generation 1/4 YR 1/4 Yr 1/4 yR 1/4 yr Sperm 1/2 YR 1/2 yr 1/4 YR YYRR YYRr YyRR YyRr 1/2 YR YYRR YyRr 1/4 Yr Eggs YYRr YYrr YyRr Yyrr Eggs Figure 14.8 Do the alleles for one character assort into gametes dependently or independently of the alleles for a different character? 1/2 yr YyRr yyrr 1/4 yR YyRR YyRr yyRR yyRr 3/4 1/4 1/4 yr Phenotypic ratio 3:1 YyRr Yyrr yyRr yyrr 9/16 3/16 3/16 1/16 Phenotypic ratio 9:3:3:1 RESULTS 315 108 101 32 Phenotypic ratio approximately 9:3:3:1

The Multiplication and Addition Rules Applied to Monohybrid Crosses The multiplication rule states that the probability that two or more independent events will occur together is the product of their individual probabilities Probability in an F1 monohybrid cross can be determined using the multiplication rule Segregation in a heterozygous plant is like flipping a coin: Each gamete has a chance of carrying the dominant allele and a chance of carrying the recessive allele Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

1/2 1/2 1/2 1/4 1/4 1/2 1/4 1/4 Rr Rr  Segregation of Segregation of Fig. 14-9 Rr Rr  Segregation of alleles into eggs Segregation of alleles into sperm Sperm 1/2 R 1/2 r R R 1/2 R R r Figure 14.9 Segregation of alleles and fertilization as chance events 1/4 1/4 Eggs r r 1/2 R r r 1/4 1/4

The rule of addition states that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities The rule of addition can be used to figure out the probability that an F2 plant from a monohybrid cross will be heterozygous rather than homozygous Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Solving Complex Genetics Problems with the Rules of Probability We can apply the multiplication and addition rules to predict the outcome of crosses involving multiple characters A dihybrid or other multicharacter cross is equivalent to two or more independent monohybrid crosses occurring simultaneously In calculating the chances for various genotypes, each character is considered separately, and then the individual probabilities are multiplied together Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

P Generation Red White CRCR CWCW Gametes CR CW Pink F1 Generation CRCW Fig. 14-10-3 P Generation Red White CRCR CWCW Gametes CR CW Pink F1 Generation CRCW Gametes 1/2 CR 1/2 CW Figure 14.10 Incomplete dominance in snapdragon color Sperm 1/2 CR 1/2 CW F2 Generation 1/2 CR CRCR CRCW Eggs 1/2 CW CRCW CWCW

(a) The three alleles for the ABO blood groups Fig. 14-11 Allele Carbohydrate IA A IB B i none (a) The three alleles for the ABO blood groups and their associated carbohydrates Red blood cell appearance Phenotype (blood group) Genotype IAIA or IA i A IBIB or IB i B Figure 14.11 Multiple alleles for the ABO blood groups IAIB AB ii O (b) Blood group genotypes and phenotypes

Fig. 14-13  AaBbCc AaBbCc Sperm 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 Eggs 1/8 1/8 Figure 14.13 A simplified model for polygenic inheritance of skin color 1/8 1/8 Phenotypes: 1/64 6/64 15/64 20/64 15/64 6/64 1/64 Number of dark-skin alleles: 1 2 3 4 5 6

Fig. 14-14 Figure 14.14 The effect of environment on phenotype

(a) Is a widow’s peak a dominant or recessive trait? Fig. 14-15b 1st generation (grandparents) Ww ww ww Ww 2nd generation (parents, aunts, and uncles) Ww ww ww Ww Ww ww 3rd generation (two sisters) WW ww Figure 14.15a Pedigree analysis or Ww Widow’s peak No widow’s peak (a) Is a widow’s peak a dominant or recessive trait?

(b) Is an attached earlobe a dominant or recessive trait? Fig. 14-15c 1st generation (grandparents) Ff Ff ff Ff 2nd generation (parents, aunts, and uncles) FF or Ff ff ff Ff Ff ff 3rd generation (two sisters) ff FF or Ff Figure 14.15b Pedigree analysis Attached earlobe Free earlobe (b) Is an attached earlobe a dominant or recessive trait?

Heterozygous phenotype same as that of homo- zygous dominant PP Pp Fig. 14-UN2 Degree of dominance Description Example Complete dominance of one allele Heterozygous phenotype same as that of homo- zygous dominant PP Pp Incomplete dominance of either allele Heterozygous phenotype intermediate between the two homozygous phenotypes CRCR CRCW CWCW Codominance Heterozygotes: Both phenotypes expressed IAIB Multiple alleles In the whole population, some genes have more than two alleles ABO blood group alleles IA , IB , i Pleiotropy One gene is able to affect multiple phenotypic characters Sickle-cell disease

Chromosomal Theory of Inheritance

Figure 15.2 The chromosomal basis of Mendel’s laws P Generation Yellow-round seeds (YYRR) Green-wrinkled seeds ( yyrr) Y y  r Y R R r y Meiosis Fertilization R Y y r Gametes All F1 plants produce yellow-round seeds (YyRr) F1 Generation R R y y r r Y Y LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. Meiosis LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. R r r R Metaphase I Y y Y y 1 1 R r r R Anaphase I Y y Y y Figure 15.2 The chromosomal basis of Mendel’s laws R r Metaphase II r R 2 2 Y y Y y y Y Y y Y Y y y Gametes R R r r r r R R 1/4 YR 1/4 yr 1/4 Yr 1/4 yR F2 Generation An F1  F1 cross-fertilization 3 3 9 : 3 : 3 : 1

CONCLUSION + P X X Generation  X Y + Sperm Eggs + + F1 + Generation + Fig. 15-4c CONCLUSION + P w w X X Generation  X Y + w w Sperm Eggs + + F1 w w + Generation w w + w Figure 15.4 In a cross between a wild-type female fruit fly and a mutant white-eyed male, what color eyes will the F1 and F2 offspring have? Sperm Eggs + + w w + F2 w Generation w w w + w

(a) (b) (c) Sperm Sperm Sperm Eggs Eggs Eggs XNXN  XnY XNXn  XNY Fig. 15-7 XNXN  XnY XNXn  XNY XNXn  XnY Sperm Xn Y Sperm XN Y Sperm Xn Y Eggs XN XNXn XNY Eggs XN XNXN XNY Eggs XN XNXn XNY XN XNXn XNY Xn XnXN XnY Xn XnXn XnY Figure 15.7 The transmission of sex-linked recessive traits (a) (b) (c)

X chromosomes Allele for orange fur Early embryo: Allele for black fur Fig. 15-8 X chromosomes Allele for orange fur Early embryo: Allele for black fur Cell division and X chromosome inactivation Two cell populations in adult cat: Active X Inactive X Active X Black fur Orange fur Figure 15.8 X inactivation and the tortoiseshell cat

b+ vg+ b vg  Parents in testcross b vg b vg b+ vg+ b vg Most or Fig. 15-UN1 b+ vg+ b vg  Parents in testcross b vg b vg b+ vg+ b vg Most offspring or b vg b vg

EXPERIMENT RESULTS Fig. 15-9-4 P Generation (homozygous) b+ b+ vg+ vg+ Wild type (gray body, normal wings) Double mutant (black body, vestigial wings)  b+ b+ vg+ vg+ b b vg vg F1 dihybrid (wild type) Double mutant TESTCROSS  b+ b vg+ vg b b vg vg Testcross offspring Eggs b+ vg+ b vg b+ vg b vg+ Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b vg Figure 15.9 How does linkage between two genes affect inheritance of characters? Sperm b+ b vg+ vg b b vg vg b+ b vg vg b b vg+ vg PREDICTED RATIOS If genes are located on different chromosomes: 1 : 1 : 1 : 1 If genes are located on the same chromosome and parental alleles are always inherited together: 1 : 1 : : RESULTS 965 : 944 : 206 : 185

YR yr Yr yR yr YyRr yyrr Yyrr yyRr Gametes from yellow-round Fig. 15-UN2 Gametes from yellow-round heterozygous parent (YyRr) YR yr Yr yR Gametes from green- wrinkled homozygous recessive parent ( yyrr) yr YyRr yyrr Yyrr yyRr Parental- type offspring Recombinant offspring

Black body, vestigial wings Fig. 15-10 Testcross parents Gray body, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) b+ vg+ b vg b vg b vg Replication of chromo- somes Replication of chromo- somes b+ vg+ b vg b+ vg+ b vg b vg b vg b vg b vg Meiosis I b+ vg+ Meiosis I and II b+ vg b vg+ b vg Meiosis II Recombinant chromosomes Figure 15.10 Chromosomal basis for recombination of linked genes b+ vg+ b vg b+ vg b vg+ Eggs Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal b vg b+ vg+ b vg b+ vg b vg+ b vg b vg b vg b vg Sperm Parental-type offspring Recombinant offspring Recombination frequency 391 recombinants =  100 = 17% 2,300 total offspring

RESULTS Recombination frequencies 9% 9.5% Chromosome 17% b cn vg Fig. 15-11 RESULTS Recombination frequencies 9% 9.5% Chromosome 17% Figure 15.11 Constructing a linkage map b cn vg

Mutant phenotypes Short aristae Black body Cinnabar eyes Vestigial Fig. 15-12 Mutant phenotypes Short aristae Black body Cinnabar eyes Vestigial wings Brown eyes 48.5 57.5 67.0 104.5 Figure 15.12 A partial genetic (linkage) map of a Drosophila chromosome Long aristae (appendages on head) Gray body Red eyes Normal wings Red eyes Wild-type phenotypes

Meiosis I Meiosis II Gametes (a) Nondisjunction of homologous Fig. 15-13-3 Meiosis I Nondisjunction Meiosis II Nondisjunction Gametes Figure 15.13 Meiotic nondisjunction n + 1 n + 1 n – 1 n – 1 n + 1 n – 1 n n Number of chromosomes (a) Nondisjunction of homologous chromosomes in meiosis I (b) Nondisjunction of sister chromatids in meiosis II

Reciprocal translocation Fig. 15-15 A B C D E F G H A B C E F G H Deletion (a) A B C D E F G H A B C B C D E F G H Duplication (b) A B C D E F G H A D C B E F G H (c) Inversion Figure 15.15 Alterations of chromosome structure A B C D E F G H M N O C D E F G H (d) Reciprocal translocation M N O P Q R A B P Q R

Fig. 15-16 Figure 15.16 Down syndrome

Translocated chromosome 22 (Philadelphia chromosome) Fig. 15-17 Reciprocal translocation Normal chromosome 9 Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome) Normal chromosome 22 Figure 15.17 Translocation associated with chronic myelogenous leukemia (CML)