Asexual reproduction (1 parent, mitosis) Fig. 13-2a 0.5 mm Parent Bud Asexual reproduction (1 parent, mitosis) (a) Hydra

(asexual reproduction) Bacteria Binary fission (asexual reproduction)

DNA – lots of it in a small space Chromosome Know how to label chromatin

Fig. 12-UN3

that control the cell cycle. They create chemical “checkpoints” Fig. 12-14 G1 checkpoint The cell cycle Cyclins are proteins that control the cell cycle. They create chemical “checkpoints” through- out the process. Control system S G1 G2 M M checkpoint G2 checkpoint

G1 S Cytokinesis Mitosis G2 MITOTIC (M) PHASE Prophase Telophase and Fig. 12-UN1 INTERPHASE G1 S Cytokinesis Mitosis G2 MITOTIC (M) PHASE Prophase Telophase and Cytokinesis Prometaphase Anaphase Metaphase

cytokinesis Fig. 12-9 Vesicles forming cell plate Wall of parent cell Cleavage furrow Cell plate New cell wall Contractile ring of microfilaments Daughter cells Daughter cells (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM)

What is the haploid number for each? Symbol for haploid? What kind of cells are haploid?

Karyotyping The process of creating a graphic display of chromosomes Fig. 13-3 APPLICATION Karyotyping The process of creating a graphic display of chromosomes from a cell to determine abnormal chromosome number. Homologues are paired up and arranged in descending order according to length. TECHNIQUE 5 µm Pair of homologous replicated chromosomes Centromere Sister chromatids Metaphase chromosome

Know the terms Key Maternal set of chromosomes (n = 3) hapolid # Fig. 13-4 Know the terms Key Maternal set of chromosomes (n = 3) hapolid # 2n = 6 Diploid number Paternal set of chromosomes (n = 3) Two sister chromatids of one replicated chromosome Centromere 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) The relationship between mitosis and meiosis Egg (n) Diploid (2n) Sperm (n) MEIOSIS FERTILIZATION Ovary Testis Diploid zygote (2n = 46) Mitosis and development Multicellular diploid adults (2n = 46)

Recombinant chromosomes Fig. 13-12-5 Prophase I of meiosis Nonsister Chromatids Homologous pair Centromere TEM Anaphase I Anaphase II Daughter cells Recombinant chromosomes

Replicated chromosome Fig. 13-9a MITOSIS MEIOSIS MEIOSIS I Parent cell Chromosome replication Chromosome replication Prophase I Prophase Homologous chromosome pair 2n = 6 Replicated chromosome Metaphase Metaphase I Anaphase Telophase Anaphase I Telophase I 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

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 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

DNA replication Meiosis I – PMAT to separate homologous pairs. Have Fig. 13-UN3 DNA replication Meiosis I – PMAT to separate homologous pairs. Have 2 cells. Meiosis II – before it starts, NO DNA replication. PMAT separates sister chromatids. Four haploid cells produced. No pairs of chromosomes.

Fig. 13-UN4

NONDISJUCTION Failure of a particular chromosome to separate properly during meiosis. Can happen in meiosis I if a particular homologous pair fails to separate. Can happen in meiosis if sister chromatids of a particular chromosome fail to separate Remember the term nondisjunction applies to abnormal gametes. In humans, abnormal egg or sperm would be 24 or 22 chromosomes.

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

NONDISJUNCTION produces abnormal gametes Fertilization involving an abnormal gamete results in a zygote with an abnormal number of a particular chromosome Ex) Down’s Syndrome – 3 copies of chromosome #21 instead of the normal 2 copies typically found in diploid cell. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Monosomy and Trisomy are words we use to describe a zygote, not a gamete. Monosomy: A monosomic zygote has only one copy of a particular chromosome. In humans an example would be Turner’s syndrome: Female child only has only 1 sex chromosome (X) in each diploid cell instead of XX, she has a total of 45 chromosomes in diploid cells instead of 46. Trisomy: A trisomic zygote has three copies of a particular chromosome. In humans an example would be Down’s Syndrome: Child has 3 copies of chromosome 21 in all diploid cells for a total of 47. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Polyploidy is common in plants, but not animals Polyploidy is a condition in which a zygote has more than two complete sets of chromosomes. Triploidy (3n) is three sets of chromosomes Tetraploidy (4n) is four sets of chromosomes Polyploidy is common in plants, but not animals Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

polyploidy

Fig. 15-16a Figure 15.16 Down syndrome

Down’s Syndrome Karyotype See #21 chromosomes Fig. 15-16b Figure 15.16 Down syndrome

CVS 2 processes for collecting fetal cells for karyotyping.

Abnormal # of Sex Chromosomes in a diploid cell Nondisjunction of sex chromosomes during meiosis can result in: Klinefelter syndrome - the result of an extra chromosome in a male, producing XXY individuals Monosomy X, called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans Poly X – 3 copies of XXX Jacob Syndrome - XYY Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Alterations of Chromosome Structure Breakage of a chromosome can lead to four types of changes in chromosome structure: Deletion removes a chromosomal segment Duplication repeats a segment Inversion reverses a segment within a chromosome Translocation moves a segment from one chromosome to another Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Chromosomal mutations 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) Chromosomal mutations 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

Disorders Caused by Structurally Altered Chromosomes The syndrome cri du chat (“cry of the cat”), results from a specific deletion in chromosome 5 A child born with this syndrome is mentally retarded and has a catlike cry; individuals usually die in infancy or early childhood Certain cancers, including chronic myelogenous leukemia (CML), are caused by translocations of chromosomes Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings