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Standardized Test Prep Resources Chapter Presentation Visual Concepts Transparencies Standardized Test Prep

Chapter 6 Table of Contents Section 1 Chromosomes Chromosomes and Cell Reproduction Table of Contents Section 1 Chromosomes Section 2 The Cell Cycle Section 3 Mitosis and Cytokinesis

Chapter 6 Section 1 Chromosomes Objectives Identify four examples of cell division in eukaryotes and one example in prokaryotes. Differentiate between a gene, a DNA molecule, a chromosome, and a chromatid. Differentiate between homologous chromosomes, autosomes, and sex chromosomes. Compare haploid and diploid cells. Predict how changes in chromosome number or structure can affect development.

Formation of New Cells by Cell Division Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell Division Cell division, also called cell reproduction, occurs in humans and other organisms at different times in their life. The formation of gametes involves yet a special type of cell division. Gametes are an organism’s reproductive cells, such as sperm or egg cells. When a cell divides, the DNA is first copied and then distributed.

Chapter 6 Gamete Section 1 Chromosomes Click below to watch the Visual Concept. Visual Concept

Formation of New Cells by Cell Division, continued Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell Division, continued Prokaryotic Cell Reproduction Prokaryotes reproduce by a type of cell division called binary fission. Binary fission is a form of asexual reproduction that produces identical offspring. In asexual reproduction, a single parent passes exact copies of all of its DNA to its offspring.

Formation of New Cells by Cell Division, continued Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell Division, continued Prokaryotic Cell Reproduction Binary fission occurs in two stages: first, the DNA is copied (so that each new cell will have a copy of the genetic information), and then the cell divides. Eventually the dividing prokaryote is pinched into two independent cells.

Chapter 6 Section 1 Chromosomes Binary Fission

Formation of New Cells by Cell Division, continued Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell Division, continued Eukaryotic Cell Reproduction A gene is a segment of DNA that codes for a protein or RNA molecule. When genes are being used, the DNA is stretched out so that the information it contains can be used to direct the synthesis of proteins. As a eukaryotic cell prepares to divide, the DNA and the proteins associated with the DNA coil into a structure called a chromosome.

Chapter 6 Gene Section 1 Chromosomes Click below to watch the Visual Concept. Visual Concept

Chapter 6 Section 1 Chromosomes Chromosome

Homologous Chromosomes Chapter 6 Section 1 Chromosomes Homologous Chromosomes

Formation of New Cells by Cell Division, continued Chapter 6 Section 1 Chromosomes Formation of New Cells by Cell Division, continued Eukaryotic Cell Reproduction The two exact copies of DNA that make up each chromosome are called chromatids. The two chromatids of a chromosome are attached at a point called a centromere. The chromatids, which become separated during cell division and placed into each new cell, ensure that each new cell will have the same genetic information as the original cell.

Chapter 6 Section 1 Chromosomes Chromosome Structure

Chapter 6 Parts of a Chromosome Section 1 Chromosomes Click below to watch the Visual Concept. Visual Concept

Comparing Cell Division in Prokaryotes and Eukaryotes Chapter 6 Section 1 Chromosomes Comparing Cell Division in Prokaryotes and Eukaryotes

How Chromosome Number and Structure Affect Development Chapter 6 Section 1 Chromosomes How Chromosome Number and Structure Affect Development Sets of Chromosomes Homologous chromosomes are chromosomes that are similar in size, shape, and genetic content. Each homologue in a pair of homologous chromosomes comes from one of the two parents. The 46 chromosomes in human somatic cells are actually two sets of 23 chromosomes.

How Chromosome Number and Structure Affect Development, continued Chapter 6 Section 1 Chromosomes How Chromosome Number and Structure Affect Development, continued Sets of Chromosomes When a cell, such as a somatic cell, contains two sets of chromosomes, it is said to be diploid. When a cell, such as a gamete, contains one set of chromosomes, it is said to be haploid. The fusion of two haploid gametes—a process called fertilization—forms a diploid zygote. A zygote is a fertilized egg cell.

Comparing Haploid and Diploid Cells Chapter 6 Section 1 Chromosomes Comparing Haploid and Diploid Cells

Chromosome Number of Various Organisms Chapter 6 Section 1 Chromosomes Chromosome Number of Various Organisms

How Chromosome Number and Structure Affect Development, continued Chapter 6 Section 1 Chromosomes How Chromosome Number and Structure Affect Development, continued Sex Chromosomes Autosomes are chromosomes that are not directly involved in determining the sex (gender) of an individual. The sex chromosomes, one of the 23 pairs of chromosomes in humans, contain genes that will determine the sex of the individual. In humans and many other organisms, the two sex chromosomes are referred to as the X and Y chromosomes.

Sex Chromosomes and Autosomes Chapter 6 Section 1 Chromosomes Sex Chromosomes and Autosomes Click below to watch the Visual Concept. Visual Concept

The Role of Sex Chromosomes in Sex Determination Chapter 6 Section 1 Chromosomes The Role of Sex Chromosomes in Sex Determination Click below to watch the Visual Concept. Visual Concept

How Chromosome Number and Structure Affect Development, continued Chapter 6 Section 1 Chromosomes How Chromosome Number and Structure Affect Development, continued Change in Chromosome Number Humans who are missing even one of the 46 chromosomes do not survive. Humans with more than two copies of a chromosome, a condition called trisomy, will not develop properly. Abnormalities in chromosome number can be detected by analyzing a karyotype, a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size.

Chapter 6 Section 1 Chromosomes Karyotype

Chapter 6 Section 1 Chromosomes Chromosome Number

Chapter 6 Karyotype Section 1 Chromosomes Click below to watch the Visual Concept. Visual Concept

How Chromosome Number and Structure Affect Development, continued Chapter 6 Section 1 Chromosomes How Chromosome Number and Structure Affect Development, continued Change in Chromosome Structure Changes in an organism’s chromosome structure are called mutations. Breakage of a chromosome can lead to four types of mutations: 1. deletion mutation 2. duplication mutation 3. inversion mutation 4. translocation mutation

Types of Chromosome Mutations Chapter 6 Section 1 Chromosomes Types of Chromosome Mutations Click below to watch the Visual Concept. Visual Concept

Chapter 6 Section 2 The Cell Cycle Objectives Identify the major events that characterize each of the five phases of the cell cycle. Describe how the cell cycle is controlled in eukaryotic cells. Relate the role of the cell cycle to the onset of cancer.

The Life of a Eukaryotic Cell Chapter 6 Section 2 The Cell Cycle The Life of a Eukaryotic Cell The Cell Cycle The cell cycle is a repeating sequence of cellular growth and division during the life of an organism. A cell spends 90 percent of its time in the first three phases of the cycle, which are collectively called interphase.

Cell Cycle Introduction Chapter 6 Section 2 The Cell Cycle Cell Cycle Introduction

The Life of a Eukaryotic Cell, continued Chapter 6 Section 2 The Cell Cycle The Life of a Eukaryotic Cell, continued The Cell Cycle The five phases of the cell cycle are: 1. First growth (G1) phase During the G1 phase, a cell grows rapidly and carries out its routine functions. 2. Synthesis (S) phase A cell’s DNA is copied during this phase. 3. Second growth (G2) phase In the G2 phase, preparations are made for the nucleus to divide. 4. Mitosis The process during cell division in which the nucleus of a cell is divided into two nuclei is called mitosis. 5. Cytokinesis The process during cell division in which the cytoplasm divides is called cytokinesis.

Chapter 6 Section 2 The Cell Cycle Cell Cycle G1 Phase

Chapter 6 Section 2 The Cell Cycle Cell Cycle S Phase

Chapter 6 Section 2 The Cell Cycle Cell Cycle G2 Phase

Chapter 6 Section 2 The Cell Cycle Cell Cycle M Phase

Control of the Cell Cycle Chapter 6 Section 2 The Cell Cycle Control of the Cell Cycle The cell cycle has key checkpoints (inspection points) at which feedback signals from the cell can trigger the next phase of the cell cycle (green light). Other feedback signals can delay the next phase to allow for completion of the current phase (yellow or red light).

Control of the Cell Cycle, continued Chapter 6 Section 2 The Cell Cycle Control of the Cell Cycle, continued Control occurs at three principal checkpoints: 1. Cell growth (G1) checkpoint This checkpoint makes the decision of whether the cell will divide. 2. DNA synthesis (G2) checkpoint DNA replication is checked at this point by DNA repair enzymes. 3. Mitosis checkpoint This checkpoint triggers the exit from mitosis.

Control of the Cell Cycle Chapter 6 Section 2 The Cell Cycle Control of the Cell Cycle Click below to watch the Visual Concept. Visual Concept

Control of the Cell Cycle, continued Chapter 6 Section 2 The Cell Cycle Control of the Cell Cycle, continued When Control Is Lost: Cancer Certain genes contain the information necessary to make the proteins that regulate cell growth and division. If one of these genes is mutated, the protein may not function, and regulation of cell growth and division can be disrupted. Cancer, the uncontrolled growth of cells, may result.

Chapter 6 Section 3 Mitosis and Cytokinesis Objectives Describe the structure and function of the spindle during mitosis. Summarize the events of the four stages of mitosis. Differentiate cytokinesis in animal and plant cells.

Chromatid Separation in Mitosis Chapter 6 Section 3 Mitosis and Cytokinesis Chromatid Separation in Mitosis During mitosis, the chromatids on each chromosome are physically moved to opposite sides of the dividing cell with the help of the spindle. Spindles are cell structures made up of both centrioles and individual microtubule fibers that are involved in moving chromosomes during cell division.

Chromatid Separation in Mitosis, continued Chapter 6 Section 3 Mitosis and Cytokinesis Chromatid Separation in Mitosis, continued Forming the Spindle When a cell enters the mitotic phase, the centriole pairs start to separate, moving toward opposite poles of the cell. As the centrioles move apart, the spindle begins to form.

Chromatid Separation in Mitosis, continued Chapter 6 Section 3 Mitosis and Cytokinesis Chromatid Separation in Mitosis, continued Separation of Chromatids by Attaching Spindle Fibers The chromatids are moved to each pole of the cell in a manner similar to bringing in a fish with a fishing rod and reel. When the microtubule “fishing line” is “reeled in,” the chromatids are dragged to opposite poles. As soon as the chromatids separate from each other they are called chromosomes.

Mitosis and Cytokinesis Chapter 6 Section 3 Mitosis and Cytokinesis Mitosis and Cytokinesis Mitosis Step 1 Prophase The nuclear envelope dissolves and a spindle forms. Step 2 Metaphase During metaphase the chromosomes move to the center of the cell and line up along the equator. Step 3 Anaphase Centromeres divide during anaphase. Step 4 Telophase A nuclear envelope forms around the chromosomes at each pole. Mitosis is complete.

Chapter 6 Section 3 Mitosis and Cytokinesis Stages of Mitosis

Snapshot of Mitotic Structures Chapter 6 Section 3 Mitosis and Cytokinesis Snapshot of Mitotic Structures Click below to watch the Visual Concept. Visual Concept

Chapter 6 Section 3 Mitosis and Cytokinesis Mitosis

Mitosis and Cytokinesis, continued Chapter 6 Section 3 Mitosis and Cytokinesis Mitosis and Cytokinesis, continued Cytokinesis As mitosis ends, cytokinesis begins. During cytokinesis, the cytoplasm of the cell is divided in half, and the cell membrane grows to enclose each cell, forming two separate cells as a result. The end result of mitosis and cytokinesis is two genetically identical cells where only one cell existed before.

Comparing Cell Division in Plants and Animals Chapter 6 Section 3 Mitosis and Cytokinesis Comparing Cell Division in Plants and Animals Click below to watch the Visual Concept. Visual Concept

Chapter 6 Multiple Choice Standardized Test Prep Multiple Choice The illustration below shows the events of the cell cycle. Use the figure below to answer questions 1–3.

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 1. For about what proportion of the cell cycle is the cell in interphase? A. less than 1/2 B. less than 3/4 C. more than 3/4 D. more than 9/10

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 1. For about what proportion of the cell cycle is the cell in interphase? A. less than 1/2 B. less than 3/4 C. more than 3/4 D. more than 9/10

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 2. List the phases of the cell cycle starting immediately after cell division. F. G1, S, G2, mitosis, cytokinesis G. cytokinesis, G1, S, G2, mitosis H. S, G2, mitosis, cytokinesis, G1 J. G1, cytokinesis, mitosis, G2, S

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 2. List the phases of the cell cycle starting immediately after cell division. F. G1, S, G2, mitosis, cytokinesis G. cytokinesis, G1, S, G2, mitosis H. S, G2, mitosis, cytokinesis, G1 J. G1, cytokinesis, mitosis, G2, S

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 3. If the phase during which DNA is synthesized did not occur, what effect would it have on the cell cycle? A. Mitosis would immediately follow S. B. Cytokinesis would immediately follow G2. C. G1 would immediately follow mitosis. D. G2 would immediately follow G1.

Multiple Choice, continued Chapter 6 Standardized Test Prep Multiple Choice, continued 3. If the phase during which DNA is synthesized did not occur, what effect would it have on the cell cycle? A. Mitosis would immediately follow S. B. Cytokinesis would immediately follow G2. C. G1 would immediately follow mitosis. D. G2 would immediately follow G1.