3-19 ATB Describe two things that make up chromosomes Objectives: Worksheet pages – 8 & 9 Review mitosis Describe meiosis

Meiosis

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

Mitosis Review What are the products of mitosis? What are the products of mitosis? 2 daughter cells 2 daughter cells Genetically – how similar are the daughter cells in mitosis? Genetically – how similar are the daughter cells in mitosis? They are identical They are identical When is the DNA copied for the new cell? When is the DNA copied for the new cell? S phase of interphase S phase of interphase What are two things make up chromosomes? What are two things make up chromosomes? DNA and histones (protein) DNA and histones (protein) What is the middle part of the chromosome? What is the middle part of the chromosome? Centromere Centromere

What does DIPLOID mean? What does DIPLOID mean? Cells having 2 homologous copies of each chromosome (2n) Cells having 2 homologous copies of each chromosome (2n) What does HAPLOID mean? What does HAPLOID mean? Number of chromosomes in a gamete (1n) or half the total number of chromosomes Number of chromosomes in a gamete (1n) or half the total number of chromosomes What is are sister chromatids? What is are sister chromatids? Identical copies of the same chromosome Identical copies of the same chromosome When does the cell produce the copy of the chromatid? When does the cell produce the copy of the chromatid? S phase S phase

What are homologous chromosomes? What are homologous chromosomes? Chromosomes that carry genes for same traits (though variation of the trait may differ) Chromosomes that carry genes for same traits (though variation of the trait may differ) Allele – variation of a trait Allele – variation of a trait Trait – flower color Trait – flower color Allele – genes for either white or purple flowers Allele – genes for either white or purple flowers

3-22 ATB What are homologous chromosomes? Are they genetically identical, or slightly different? Objectives: Quiz – maybe Weds or Thurs Describe meiosis, synapsis, tetrads and crossing over

Formation of Haploid Cells Meiosis - Meiosis - is a process of division that reduces the number of chromosomes in new cells to half the number in the original cell. is a process of division that reduces the number of chromosomes in new cells to half the number in the original cell. 2n cells  1n cells 2n cells  1n cells Occurs in our sex cells Occurs in our sex cells Four new haploid cells result (gametes) Four new haploid cells result (gametes) Meiosis is broken down into Meiosis I and Meiosis II. Meiosis is broken down into Meiosis I and Meiosis II.

During meiosis… Synapsis – Pairing of homologous chromosomes during prophase I This did not occur in mitosis Tetrad – Two pairs of homologous chromosomes

Formation of Haploid Cells Crossing-over – Crossing-over – when portions of homologous chromosomes exchange genetic material when portions of homologous chromosomes exchange genetic material Occurs during prophase I and results in genetic recombination. Occurs during prophase I and results in genetic recombination. Genetic recombination – Genetic recombination – Regrouping of genes in an offspring that results in a genetic makeup that is different from the parents Regrouping of genes in an offspring that results in a genetic makeup that is different from the parents

Chapter 8 Tetrads and Crossing-over of Genetic Material Section 3 Meiosis

Crossing Over

Why is genetic recombination important? Asexual Reproduction Asexual Reproduction Genes identical to parents Genes identical to parents PRO: Offspring well adapted to survival PRO: Offspring well adapted to survival Need only one parent Need only one parent CON: If susceptible to a disease that may kill off the entire population (b/c all genes the same) CON: If susceptible to a disease that may kill off the entire population (b/c all genes the same) Sexual Reproduction Sexual Reproduction PRO: Leads to genetic diversity from parents PRO: Leads to genetic diversity from parents Not all members will die from a disease (leads to specie evolution) Not all members will die from a disease (leads to specie evolution) CON: Need two parents CON: Need two parents

3-23 ATB What is crossing over? Why does it occur? Objectives: Discuss nondisjunction and independent assortment Read book pages Answer Questions, #1, #3, #5, #6, #7, #8, #9

Error in Meiosis Nondisjunction - Nondisjunction - When a set of homologous chromosomes do not separate during metaphase When a set of homologous chromosomes do not separate during metaphase "not coming apart" "not coming apart" Results in gametes with incorrect chromosome # Results in gametes with incorrect chromosome # Results: Results: If fertilization occurs, most fetus will die If fertilization occurs, most fetus will die Down Syndrome – trisomy 21 Down Syndrome – trisomy 21 Edwards syndrome trisomy 18 Edwards syndrome trisomy 18 Turners Syndrome – monosomy X Turners Syndrome – monosomy X Triple-X syndrome – trisomy X Triple-X syndrome – trisomy X Klinefelters Syndrome - XXy Klinefelters Syndrome - XXy

Independent Assortment – Independent Assortment – Random separation of homologous chromosomes during anaphase I Random separation of homologous chromosomes during anaphase I Results in genetic variation Results in genetic variation

How does meiosis ensure genetic variation? Independent assortment – homologous chromosomes separate randomly Independent assortment – homologous chromosomes separate randomly Means sperm or egg will randomly receive various alleles for genes Means sperm or egg will randomly receive various alleles for genes Crossing over – chromosomes that are donated to the offspring are different from the parents Crossing over – chromosomes that are donated to the offspring are different from the parents

Chapter 8 Comparing Meiosis and Mitosis Section 3 Meiosis

Development of Gametes Spermatogenesis - Spermatogenesis - is the process by which sperm cells are produced. is the process by which sperm cells are produced. Oogenesis – Oogenesis – is the process that produces mature egg cells. is the process that produces mature egg cells. Polar Bodies – Polar Bodies – Three other products of oogenesis Three other products of oogenesis Eventually break down – only one egg produced Eventually break down – only one egg produced One egg gets majority of cytoplasm One egg gets majority of cytoplasm

Read book pages Answer questions #1, #3, #4 - #6, #8, #9 If you do not get done in class it is homework. If you are going to use the online book, you must write the question down before you leave. Or just borrow a book (but you must let me know)

3-24 ATB What is oogenesis? What is produced? Objectives: Describe sexual reproduction and it’s benefits. Compare mitosis and meiosis Quiz – Thursday Review sheet due Thursday

Meiosis in Male and Female Animals

Sexual Reproduction Sexual reproduction – Sexual reproduction – is the formation of offspring through meiosis and the union of a sperm and an egg. 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. Offspring produced by sexual reproduction are genetically different from the parents. Why? Why? ½ genes from different parent ½ genes from different parent b/c of crossing over, chromosomes received are different from parent’s original b/c of crossing over, chromosomes received are different from parent’s original Independent assortment Independent assortment

Sexual Reproduction

The End

Multiple Choice 1. Which of the following statements about prokaryotic chromosomes is true? A. Prokaryotes have at least two chromosomes. B. Prokaryotic chromosomes consist of a circular DNA molecule. C. Prokaryotic chromosomes include histone and nonhistone proteins. D. Prokaryotic chromosomes are made of DNA wrapped tightly around histone proteins. Standardized Test Prep Chapter 8

Multiple Choice, continued 1. Which of the following statements about prokaryotic chromosomes is true? A. Prokaryotes have at least two chromosomes. B. Prokaryotic chromosomes consist of a circular DNA molecule. C. Prokaryotic chromosomes include histone and nonhistone proteins. D. Prokaryotic chromosomes are made of DNA wrapped tightly around histone proteins. Standardized Test Prep Chapter 8

Multiple Choice, continued 2. Crossing-over occurs during which process? F. mitosis G. meiosis I H. meiosis II J. interphase Standardized Test Prep Chapter 8

Multiple Choice, continued 2. Crossing-over occurs during which process? F. mitosis G. meiosis I H. meiosis II J. interphase Standardized Test Prep Chapter 8

Multiple Choice, continued 3. In which phase of mitosis do chromatids separate and become individual chromosomes? A. prophase B. metaphase C. anaphase D. telophase/cytokinesis Chapter 8 Standardized Test Prep The graph below shows the relative mass of DNA and chromosome number for a cell undergoing mitosis. Use the graph to answer the questions that follow.

Multiple Choice, continued 3. In which phase of mitosis do chromatids separate and become individual chromosomes? A. prophase B. metaphase C. anaphase D. telophase/cytokinesis Chapter 8 Standardized Test Prep The graph below shows the relative mass of DNA and chromosome number for a cell undergoing mitosis. Use the graph to answer the questions that follow.

Multiple Choice, continued 4. What process occurs that leads to the decrease in the cell’s DNA mass? F. prophase G. metaphase H. anaphase J. telophase/cytokinesis Chapter 8 Standardized Test Prep The graph below shows the relative mass of DNA and chromosome number for a cell undergoing mitosis. Use the graph to answer the questions that follow.

Multiple Choice, continued 4. What process occurs that leads to the decrease in the cell’s DNA mass? F. prophase G. metaphase H. anaphase J. telophase/cytokinesis Chapter 8 Standardized Test Prep The graph below shows the relative mass of DNA and chromosome number for a cell undergoing mitosis. Use the graph to answer the questions that follow.

Multiple Choice, continued 5. prokaryote : binary fission :: eukaryote : A. mitosis B. cytokinesis C. crossing-over D. genetic recombination Chapter 8 Standardized Test Prep

Multiple Choice, continued 5. prokaryote : binary fission :: eukaryote : A. mitosis B. cytokinesis C. crossing-over D. genetic recombination Chapter 8 Standardized Test Prep

Multiple Choice, continued 6. Which type of cell division is shown in the diagram? F. mitosis G. meiosis H. binary fission J. sexual reproduction Chapter 8 Standardized Test Prep The diagram below shows a model of cell division. Use the diagram to answer the question that follows.

Multiple Choice, continued 6. Which type of cell division is shown in the diagram? F. mitosis G. meiosis H. binary fission J. sexual reproduction Chapter 8 Standardized Test Prep The diagram below shows a model of cell division. Use the diagram to answer the question that follows.

Short Response Human cells are either diploid or haploid. All human cells with 46 chromosomes are diploid. Would a human cell with any 23 chromosomes be haploid? Explain your answer. Chapter 8 Standardized Test Prep

Short Response, continued Human cells are either diploid or haploid. All human cells with 46 chromosomes are diploid. Would a human cell with any 23 chromosomes be haploid? Explain your answer. Answer: No, a haploid cell has one complete set of chromosomes, which in the case of humans is 23. Randomly having 23 chromosomes would not be considered haploid. Chapter 8 Standardized Test Prep

Extended Response For a cell to function efficiently, its surface area must exceed that of its volume. Part A Explain how cell division maintains the relationship between surface area and volume. Part B How does a stable ratio between surface area and volume help maintain proper cell functioning? Chapter 8 Standardized Test Prep

Extended Response, continued Answer: Part A The smaller the cell, the greater is the ratio of surface area to volume. Cell division makes one larger cell into two smaller cells. Part B By having a stable ratio between surface area and volume, cells are able to maintain homeostasis by taking in and getting rid of substances efficiently through osmosis and diffusion. Chapter 8

Stages of Mitosis