State Standard 2E. Compare the advantages of sexual reproduction and asexual reproduction in different situations. Meiosis & Sexual Reproduction (10.1)

 Human body cells have 46 chromosomes 10.1 Meiosis Sexual Reproduction and Genetics  Each parent contributes 23 chromosomes Chapter 10  Homologous chromosomes—one of two paired chromosomes, one from each parent Chromosomes & Chromosome Number

Chromosomes & Chromosome Number Cont’d 10.1 Meiosis Sexual Reproduction and Genetics  Same length  Same centromere position  Carry genes that control the same inherited traits Chapter 10 Homologous Chromosomes have…

These chromosomes have replicated These chromosomes Have not replicated

Haploid and Diploid Cells Sexual Reproduction and Genetics  Gametes are haploid. The contain half the normal # of chromosomes for the organism. (n) Human gametes = 23 chromosomes  All other body cells (aka somatic cells) are diploid. They contain the normal # of chromosomes for the organism. (2n) Human body cells = 46 chromosomes Meiosis  An organism produces gametes to maintain the same number of chromosomes from generation to generation. Chapter 10

Meiosis  Meiosis is a special type of cell division that produces gametes.  Gametes are haploid (n) cells Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 When 2 gametes combine during fertilization, the normal (2n) number of chromosomes is restored.

Stages of Meiosis  Meiosis reduces the chromosome number (2n) to half (n) through the separation of homologous chromosomes  Human meiosis reduces the cell from 46 to 23 chromosomes. Sexual Reproduction and Genetics  Involves two consecutive cell divisions called Meiosis I and Meiosis II 10.1 Meiosis Chapter 10

Meiosis I - Interphase Sexual Reproduction and Genetics 10.1 Meiosis  Chromosomes replicate.  Chromatin condenses. Chapter 10 Interphase

Meiosis I – Prophase I Sexual Reproduction and Genetics 10.1 Meiosis  Pairing of homologous chromosomes occurs. (called synapsis)  Each chromosome consists of two chromatids.  The nuclear envelope breaks down.  Spindles form. Chapter 10 Prophase I

Meiosis I – Prophase I Cont’d Sexual Reproduction and Genetics 10.1 Meiosis  During Prophase I, crossing over creates genetic variation.  Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes. Chapter 10

Meiosis I – Metaphase I Sexual Reproduction and Genetics 10.1 Meiosis  Chromosome centromeres attach to spindle fibers.  Homologous chromosomes line up at the equator. Chapter 10 Metaphase I

Meiosis I – Anaphase I Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 Anaphase I  Entire homologous chromosomes separate and move to opposite poles of the cell.

Meiosis I – Telophase I Sexual Reproduction and Genetics 10.1 Meiosis  The spindles break down.  Chromosomes uncoil and form two nuclei.  The cell divides.  There is no interphase following Meiosis I Chapter 10 Telophase I

Meiosis II – Prophase II Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10  A second set of phases begins as the spindle apparatus forms and the chromosomes condense.  Meiosis II is like mitosis. Prophase II

Meiosis II – Metaphase II Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10  A haploid number of chromosomes line up at the equator. Metaphase II

Meiosis II – Anaphase II Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 Anaphase II  The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.

Sexual Reproduction and Genetics 10.1 Meiosis Meiosis II – Telophase II Chapter 10  The chromosomes reach the poles, and the nuclear membrane and nuclei reform. Telophase II

Meiosis II - Cytokinesis Sexual Reproduction and Genetics  Cytokinesis results in four haploid cells, each with n number of chromosomes.  The 4 daughter cells are genetically unique Meiosis Chapter 10 Cytokinesis

The Importance of Meiosis  Meiosis consists of two sets of divisions Sexual Reproduction and Genetics  Produces four haploid daughter cells that are not identical 10.1 Meiosis  Results in genetic variation Chapter 10

Other Concepts in Sexual Reproduction Fertilization- the joining of a sperm & egg to form a fertilized egg cell called a zygote.

Other Concepts in Sexual Reproduction Pollination in Plants - when pollen grains (sperm cells) from a seed plant land on the female reproductive structure of the plant. This leads to fertilization & seed formation. This process is aided by wind & animals

Other Concepts in Sexual Reproduction Conjugation - A process in which two cells (prokaryotic or protist) connect to each other and exchange genetic information – thereby increasing genetic variation.

Sexual Reproduction and Genetics Sexual vs. Asexual Reproduction Asexual reproduction  The organism inherits all of its chromosomes from a single parent.  The new individual is genetically identical to its parent Meiosis Chapter 10 Advantages: Doesn’t require a partner, faster, works well in a stable environment. Disadvantages: No genetic variation. A major environmental change can wipe out a species.

Sexual Reproduction and Genetics Sexual vs. Asexual Reproduction Sexual reproduction  The organism inherits different genetic info from each parent.  The new individual is genetically unique from its parents Meiosis Chapter 10 Advantages: More genetic variation means possible survival in a changing environment. Disadvantages: Slower, 2 parents & mating required.

1.A 2.B 3.C 4.D FQ 7 Sexual Reproduction and Genetics Chapter Formative Questions In rabbits, gray fur (G) is dominant to black fur (g). If a heterozygous male is crossed with a heterozygous female, what is the phenotypic ratio of the possible offspring? A. 1:1 B. 1:2:1 C. 2:1 D. 3:1

1.A 2.B 3.C 4.D FQ 8 Sexual Reproduction and Genetics Chapter 10 Which explains how the shuffling of genes during meiosis results in billions of possible combinations? A. crossing over B. gene linkage C. genetic recombination D. independent segregation 10.3 Formative Questions

1.A 2.B FQ 9 Sexual Reproduction and Genetics Chapter Formative Questions Two genes on the same chromosome may become separated during meiosis. A. true B. false

1.A 2.B 3.C 4.D FQ 10 Sexual Reproduction and Genetics Chapter Formative Questions What is the term for an organism that has one or more sets of extra chromosomes in its cells? A. diploid B. gamete C. hybrid D. polyploid

1.A 2.B 3.C 4.D CAQ 1 Sexual Reproduction and Genetics Chapter 10 A. 6 B. 12 C. 24 D. 36 How many chromosomes would a cell have during metaphase I of meiosis if it has 12 chromosomes during interphase? Chapter Assessment Questions

1.A 2.B 3.C 4.D CAQ 2 Sexual Reproduction and Genetics Chapter 10 Chapter Assessment Questions A. prophase I B. interphase C. anaphase I D. anaphase II Which stage of meiosis is illustrated?

1.A 2.B 3.C 4.D CAQ 3 Sexual Reproduction and Genetics Chapter 10 Chapter Assessment Questions What is the next step for the chromosomes illustrated? A. Chromosomes replicate. B. Chromosomes move to opposite poles. C. Chromosomes uncoil and form two nuclei. D. Chromosomes line up at the equator.

1.A 2.B 3.C 4.D Standardized Test Practice STP 1 Sexual Reproduction and Genetics Chapter 10 What is this process called? A. fertilization B. gamete formation C. inheritance D. reproduction

1.A 2.B 3.C 4.D Standardized Test Practice STP 2 Sexual Reproduction and Genetics Chapter 10 Before meiosis I, the sister chromatids of this chromosome were identical. What process caused a change in a section of one chromatid? A. DNA replication B. crossing over C. synapsis D. telophase

1.A 2.B 3.C 4.D Standardized Test Practice STP 3 Sexual Reproduction and Genetics Chapter 10 At what stage is the chromosome number reduced from 2n to n? A. prophase I B. metaphase I C. anaphase I D. meiosis II

1.A 2.B 3.C 4.D Standardized Test Practice STP 4 Sexual Reproduction and Genetics Chapter 10 To which step in this process does the law of segregation apply? A. grows into plant B. gamete formation C. fertilization D. seed development

1.A 2.B 3.C 4.D Standardized Test Practice STP 5 Sexual Reproduction and Genetics Chapter 10 For human eye color, brown is dominant and blue is recessive. If a husband is heterozygous and his wife has blue eyes, what is the probability that their child will have blue eyes? A. 0 B. 1/4 C. 1/2 D. 1