Cell ReproductionChapter 8

Table of Contents

Section 1 Chromosomes

Section 2 Cell Division

Section 3 Meiosis

Section 1 Chromosomes

Chapter 8

Objectives

• 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.

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.

Chapter 8

Chromosome Structure

Section 1 Chromosomes

Section 1 Chromosomes

Chapter 8

Chromosome Structure, continued

• Chromosomes in prokaryotes are simpler in structure than chromosomes in eukaryotes.

Section 1 Chromosomes

Chapter 8

Chromosome Numbers

• Each species has a characteristic number of chromosomes in each cell.

Chapter 8

Chromosome Numbers of Various Organisms

Section 1 Chromosomes

Section 1 Chromosomes

Chapter 8

Chromosome Numbers, continued

• Sex Chromosomes and Autosomes– Sex chromosomes are chromosomes that

determine the sex of an organism. – All of the other chromosomes in an organism are

autosomes.

Section 1 Chromosomes

Chapter 8

Chromosome Numbers, continued

• Diploid and Haploid Cells– Cells having two sets of chromosomes are diploid

(2n). – Haploid cells (1n) have only one set of

chromosomes.

Section 2 Cell Division

Chapter 8

Objectives

•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.

Section 2 Cell Division

Chapter 8

Cell Division in Prokaryotes

•Cell division is the process by which cells reproduce themselves.

Section 2 Cell Division

Chapter 8

Cell Division in Prokaryotes, continued

•Binary fission is the process of cell division in prokaryotes.

Section 2 Cell Division

Chapter 8

Cell Division in Eukaryotes

•Cell Cycle

–The cell cycle is the repeating set of 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.

Section 2 Cell Division

Chapter 8

Cell Division in Eukaryotes, continued

•Interphase

–Interphase consists of growth (G1), DNA replication, and preparation for cell division

(G2).

Section 2 Cell Division

Chapter 8

Stages of Mitosis

•Mitosis is divided into stages: prophase, metaphase, anaphase, and telophase.

•Mitosis results in two offspring cells that are genetically identical to the original cell.

Chapter 8

Stages of Mitosis

Section 2 Cell Division

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.

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.

Section 2 Cell Division

Chapter 8

Control of Cell Division, continued

•When Control is Lost: Cancer

–Cancer may result if cells do not respond to control mechanisms.

Section 3 Meiosis

Chapter 8

Objectives

•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.

Section 3 Meiosis

Chapter 8

Formation of Haploid Cells

•Meiosis is a process of nuclear division that reduces the number of chromosomes in new

cells to half the number in the original cell.

•Meiosis produces haploid gametes.

Section 3 Meiosis

Chapter 8

Formation of Haploid Cells, continued

•Meiosis is a process of nuclear division that reduces the number of chromosomes in new

cells to half the number in the original cell.

•Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis.

Section 3 Meiosis

Chapter 8

Meiosis I

•Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.

•Crossing-over, which is when portions of homologous chromosomes exchange genetics

material, occurs during prophase I and results in genetic recombination.

Section 3 Meiosis

Chapter 8

Meiosis II

•Meiosis II includes prophase II, metaphase II, anaphase II, and telophase II.

•Four new haploid cells result.

Chapter 8

Section 3 Meiosis

Stages of Meiosis

Section 3 Meiosis

Chapter 8

Development of Gametes

•Spermatogenesis is the process by which sperm cells are produced.

•Oogenesis is the process that produces mature egg cells.

Chapter 8

Meiosis in Male and Female Animals

Section 3 Meiosis

Section 3 Meiosis

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 the parents.