Chapter 8 Objectives Section 1 Chromosomes Describe the structure of a chromosome. Identify the differences in structure between prokaryotic chromosomes and eukaryotic chromosomes. Compare the numbers of chromosomes in different species. Explain the differences between sex chromosomes and autosomes. Distinguish between diploid and haploid cells.

Chapter 8 Chromosome Structure Section 1 Chromosomes Chapter 8 Chromosome Structure Chromosomes are rod-shaped structures made of DNA and protein. In eukaryotes, DNA wraps around proteins called histones to help maintain the compact structure of chromosomes. This allows the DNA to fit within the cell

Chapter 8 Chromosome Structure Figure 8-1 Page 151 Section 1 Chromosomes Chapter 8 Figure 8-1 Page 151 Chromosome Structure As a cell prepares to divide, its DNA coils around histones and twists into rod-shaped chromosomes

Chromosome Structure, continued Section 1 Chromosomes Chapter 8 Chromosome Structure, continued Open books to page 152, figure 8-2 Chromatids are duplicate halves of a chromosome The point at which both chromatids are attached is called the centromere (like the point where an X comes together)

Chromosome Structure, continued Section 1 Chromosomes Chapter 8 Chromosome Structure, continued Comparing chromosome structure of prokaryotes and eukaryotes Prokaryotes (bacteria) Eukaryotes (plants and animals) simple complex circular linear attached to cell membrane found free in nucleus one many

Chromosome Numbers of Various Organisms Section 1 Chromosomes Chapter 8 Chromosome Numbers of Various Organisms Each species has a characteristic number of chromosomes in each cell. Similar to Table 8-1 on page 152

Chromosome Numbers, continued Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued Sex Chromosomes and Autosomes Sex chromosomes are chromosomes that determine the sex of an organism. In humans, sex chromosomes are either X or Y Females XX Males XY All of the other chromosomes in an organism are autosomes.

Chromosome Numbers, continued Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued Breakdown of Human chromosomes 46 chromosomes total 2 are sex chromosomes, 44 are autosomes Karotype is a pictomicrograph of chromosomes in a normal dividing cell found in a human Figure 8-3 on page 153

Chromosome Numbers, continued Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued 1n Diploid cells: have two homologues of each chromosome, is designated by the symbol 2n, and has chromosomes found in pairs Haploid cells: are the reproductive cells or Gametes (sperm and egg), have ½ the number of chromosomes that are present in diploid, and is designated by the symbol 1n 1n

Chromosome Numbers, continued When gametes- a sperm cell (1n) and egg cell (1n) combine to create a new organism, the new cell will be diploid (2n). If the reproductive cells were diploid, the new cell would have too many chromosomes and would not be functional Gametes

Chapter 8 Objectives Section 2 Cell Division Describe the events of cell division in prokaryotes. Name the two parts of the cell that are equally divided during cell division in eukaryotes. Summarize the events of interphase. Describe the stages of mitosis. Compare cytokinesis in animal cells with cytokinesis in plant cells. Explain how cell division is controlled.

Cell Division in Prokaryotes Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes Cell division is the process by which cells reproduce themselves. Approximately 2 trillion cells are produced by an adult human body every day

Cell Division in Prokaryotes, continued Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes, continued Binary fission is the process of cell division in prokaryotes. Remember that bacteria is considered a prokaryote…hint hint hint Page 154 Figure 8-4

Cell Division in Eukaryotes Section 2 Cell Division Chapter 8 Cell Division in Eukaryotes Cell Cycle The cell cycle is the repeating set of 5 events in the life of a cell. The cell cycle consists of cell division and interphase. Cell division in eukaryotes includes nuclear division, called mitosis, and the division of cytoplasm, called cytokinesis.

Cell Division in Eukaryotes, Section 2 Cell Division Chapter 8 Cell Division in Eukaryotes, Look at figure 8-5 page 155 Cell cycle starts at G1 and continues through cytokinesis Correct sequence would be: G1-S-G2-M-C Make sure you know what occurs at each of those stages Interphase consists of growth (G1), DNA replication (S), and preparation for cell division (G2). Occupies most of the cell’s life

Chapter 8 Stages of Mitosis Section 2 Cell Division Chapter 8 Stages of Mitosis Mitosis is divided into 4 stages: prophase, metaphase, anaphase, and telophase. Mitosis results in two offspring cells that are genetically identical to the original cell. Follow along, pages 156-157 Use Figure 8-6, page 156

“WIND UP” “MIDDLE” Chapter 8 Stages of Mitosis Section 2 Cell Division Chapter 8 Stages of Mitosis Prophase – 1st phase of mitosis chromosomes grouped Centrosomes move towards poles of the cell and start to form spindle fibers Metaphase – 2nd phase of mitosis chromosomes move to center (middle) “WIND UP” “MIDDLE”

“APART” “TWO” Chapter 8 Stages of Mitosis Section 2 Cell Division Chapter 8 Stages of Mitosis “APART” Anaphase – 3rd phase of mitosis Chromatids of each chromosome will split Telophase – 4th phase of mitosis Chromosomes reach opposite end of original cell “TWO”

Chapter 8 Stages of Mitosis Cytokinesis – NOT a phase of mitosis Section 2 Cell Division Chapter 8 Stages of Mitosis Cytokinesis – NOT a phase of mitosis Cell splits into two cells that will be genetically identical to original cell

Section 2 Cell Division Chapter 8 Cytokinesis During cytokinesis in animal cells, a cleavage furrow pinches in and eventually separates the dividing cell into two cells. In plant cells, a cell plate separates the dividing cell into two cells after the formation of a cell wall

Chapter 8 Stages of Mitosis Put these 4 illustrations in order Section 2 Cell Division Chapter 8 Stages of Mitosis Put these 4 illustrations in order Looking above, which stage are the centromeres dividing? Which illustration above shows the starting point for mitosis?

Chapter 8 Stages of Mitosis Section 2 Cell Division Put these 4 illustrations in order 3, 2, 1, 4 Looking above, which stage are the centromeres dividing? 1 (Anaphase) Which illustration above shows the starting point for mitosis? 3 (Prophase)

Control of Cell Division Section 2 Cell Division Chapter 8 Control of Cell Division Cell division in eukaryotes is controlled by many proteins. Control occurs at three main checkpoints. G1: If cell is healthy and has suitable size during G1 phase, proteins will initiate DNA synthesis, if not healthy enough cell division stops G2: DNA repair enzymes check the results of DNA replication, if passed they will allow cell to continue to steps of mitosis Mitosis checkpoint: If the cell passes this checkpoint, proteins signal the cell to exit mitosis. The cell the enters into the G1 phase again

Control of Cell Division, continued Section 2 Cell Division Mitosis Song Chapter 8 Control of Cell Division, continued When Control is Lost: Cancer Cancer may result if cells do not respond to control mechanisms. (checkpoint stops don’t work) Cancer is the uncontrolled growth of cells (tumors)

Chapter 8 Objectives Section 3 Meiosis Compare the end products of meiosis with those of mitosis. Summarize the events of meiosis I. Explain crossing-over and how it contributes to the production of unique individuals. Summarize the events of meiosis II. Compare spermatogenesis and oogenesis. Define sexual reproduction.

Formation of Haploid Cells Section 3 Meiosis Chapter 8 Formation of Haploid Cells Meiosis - nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. Cells undergoing meiosis divide twice

Meiosis leads to four haploid cells or 1n (gametes- sex cells) rather than two diploid or 2n cells as in mitosis. 2n 2n 2n 2n 1n

Section 3 Meiosis Chapter 8 Meiosis I Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I. Make sure that you know the differences between the meiosis and mitosis phases – they do have the same names Crossing-over- homologous chromosomes exchange genetics material and results in genetic recombination (mixing up of DNA) Crossing-over acts as a source of variation within a species

-Each pair of homologue chromosomes is called a tetrad. Section 3 Meiosis Chapter 8 Follow along by looking at Figure 8-11 pages 162-163 Meiosis I Prophase I: -DNA coils into chromosomes which line up next to their homolog This pairing up is called synapsis. -Each pair of homologue chromosomes is called a tetrad. Metaphase I: -Tetrads line up along the middle of the cell.

Chapter 8 Meiosis I Anaphase I Section 3 Meiosis Chapter 8 Meiosis I Anaphase I –Homologous chromosome moves to opposite pole of dividing cell The random separation of homologous chromosomes is called independent assortment, which results in genetic variation Telophase I and Cytokinesis I – chromosomes reach opposite end cytokinesis begins, New cells contain haploid number of chromosomes

Section 3 Meiosis Chapter 8 Meiosis I Meiosis I – original cell produces 2 new cells, each containing 1 chromosome from each homologous pair. New cells contain half the number of chromosomes of original cell, however, each new cell contains two copies (as chromatids) because the original cell copied its DNA before meiosis I

Section 3 Meiosis Chapter 8 Meiosis II Meiosis II occurs in each cell formed during Meiosis I and is not preceded by the copying of DNA Meiosis II includes prophase II, metaphase II, anaphase II, and telophase II Four new haploid cells result

Section 3 Meiosis Chapter 8 Meiosis II Prophase II – spindle fibers form and begin to move chromosomes toward middle of the dividing cell Metaphase II – chromosomes move to middle of the dividing cell, -each chromatid faces opposite of the dividing cell

Chapter 8 Meiosis II Anaphase II Section 3 Meiosis Chapter 8 Meiosis II Anaphase II – chromatids separate and move toward opposite poles of the cell Telophase II -nuclear membrane forms around the chromosomes in each of the four new cells Cytokinesis II four new haploid cells Each of the new cells contain half of the original cell’s number of chromosomes

Section 3 Meiosis Chapter 8 Stages of Meiosis

1n 1n Chapter 8 Development of Gametes aka Sex Cells Section 3 Meiosis Chapter 8 Development of Gametes aka Sex Cells Spermatogenesis is the process by which sperm cells are produced. Oogenesis is the process that produces mature egg cells. 1n 1n

Meiosis in Male and Female Animals Section 3 Meiosis Chapter 8 Meiosis in Male and Female Animals 2n 1n

Chapter 8 Sexual Reproduction Section 3 Meiosis Meiosis Video Chapter 8 Sexual Reproduction Sexual reproduction is the formation of offspring through meiosis and the union of a sperm and an egg. Offspring produced by sexual reproduction are genetically different from their parents.