Sexual Reproduction and Genetics Section 1: Meiosis Section 2: Mendelian Genetics Section 3: Gene Linkage and Polyploidy Click on a lesson name to select.

Chromosomes and Chromosome Number Section 1 Sexual Reproduction and Genetics Meiosis Chromosomes and Chromosome Number Human body cells have 46 chromosomes Each parent contributes 23 chromosomes Homologous chromosomes—one of two paired chromosomes, one from each parent

Chromosomes and Chromosome Number Section 1 Sexual Reproduction and Genetics Meiosis Chromosomes and Chromosome Number Same length Same centromere position Carry genes that control the same inherited traits

Haploid and Diploid Cells Section 1 Sexual Reproduction and Genetics Meiosis Haploid and Diploid Cells An organism produces gametes to maintain the same number of chromosomes from generation to generation. Human gametes contain 23 chromosomes. A cell with n chromosomes is called a haploid cell. A cell that contains 2n chromosomes is called a diploid cell.

The sexual life cycle in animals involves meiosis. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I The sexual life cycle in animals involves meiosis. Meiosis produces gametes. When gametes combine in fertilization, the number of chromosomes is restored.

Section 1 Sexual Reproduction and Genetics Meiosis Stages of Meiosis I Reduces the chromosome number by half through the separation of homologous chromosomes Involves two consecutive cell divisions called meiosis I and meiosis II

Chromosomes replicate. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Interphase Chromosomes replicate. Chromatin condenses. Interphase

Pairing of homologous chromosomes occurs. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Prophase I Pairing of homologous chromosomes occurs. Each chromosome consists of two chromatids. Prophase I The nuclear envelope breaks down. Spindles form.

Crossing over produces exchange of genetic information. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Prophase I Crossing over produces exchange of genetic information. Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

Chromosome centromeres attach to spindle fibers. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Metaphase I Chromosome centromeres attach to spindle fibers. Metaphase I Homologous chromosomes line up at the equator.

Homologous chromosomes separate and move Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Anaphase I Homologous chromosomes separate and move to opposite poles of the cell. Anaphase I

The spindles break down. Section 1 Sexual Reproduction and Genetics Meiosis Meiosis I Telophase I The spindles break down. Telophase I Chromosomes uncoil and form two nuclei. The cell divides.

A second set of phases begins Section 1 Sexual Reproduction and Genetics Meiosis Meiosis II Prophase II A second set of phases begins as the spindle apparatus forms and the chromosomes condense. Prophase II

A haploid number of chromosomes Section 1 Sexual Reproduction and Genetics Meiosis Meiosis II Metaphase II A haploid number of chromosomes line up at the equator. Metaphase II

The sister chromatids are Section 1 Sexual Reproduction and Genetics Meiosis Meiosis II Anaphase II The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell. Anaphase II

The chromosomes reach the poles, and Section 1 Sexual Reproduction and Genetics Meiosis Meiosis II Telophase II The chromosomes reach the poles, and the nuclear membrane and nuclei reform. Telophase II

Section 1 Sexual Reproduction and Genetics Meiosis Meiosis II Cytokinesis results in four haploid cells, each with n number of chromosomes. Cytokinesis

Section 1 Sexual Reproduction and Genetics

The Importance of Meiosis Section 1 Sexual Reproduction and Genetics Meiosis The Importance of Meiosis Meiosis consists of two sets of divisions Produces four haploid daughter cells that are not identical Results in genetic variation

Chapter Table 10.1 Mitosis and Meiosis Sexual Reproduction and Genetics Table 10.1 Mitosis and Meiosis

Meiosis Provides Variation Section 1 Sexual Reproduction and Genetics Meiosis Meiosis Provides Variation Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result. Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

Sexual Reproduction v. Asexual Reproduction Section 1 Sexual Reproduction and Genetics Meiosis Sexual Reproduction v. Asexual Reproduction Asexual reproduction The organism inherits all of its chromosomes from a single parent. The new individual is genetically identical to its parent. Sexual reproduction Beneficial genes multiply faster over time.

Which symbol is used to represent the Chapter Sexual Reproduction and Genetics Chapter Diagnostic Questions Which symbol is used to represent the number of chromosomes in a gamete? # x r n A B C D CDQ 1

Segments of DNA that control the production Chapter Sexual Reproduction and Genetics Section 1 Formative Questions Segments of DNA that control the production of proteins are called _______. chromatids chromosomes genes traits A B C D FQ 1

What is the term for a pair of chromosomes Chapter Sexual Reproduction and Genetics Section 1 Formative Questions What is the term for a pair of chromosomes that have the same length, same centromere position, and carry genes that control the same traits? diploid heterozygous homozygous homologous A B C D FQ 2

Chapter Sexual Reproduction and Genetics Section 1 Formative Questions How does the number of chromosomes in gametes compare with the number of chromosomes in body cells? Gametes have 1/4 the number of chromosomes. Gametes have 1/2 the number of chromosomes. Gametes have the same number of chromosomes. Gametes have twice as many chromosomes. A B C D FQ 3

What type of organisms only reproduce asexually? Chapter Sexual Reproduction and Genetics Section 1 Formative Questions What type of organisms only reproduce asexually? bacteria protists plants simple animals A B C D FQ 4

Two genes on the same chromosome may become separated during meiosis. Chapter Sexual Reproduction and Genetics Section 3 Formative Questions Two genes on the same chromosome may become separated during meiosis. true false A B FQ 9

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

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

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

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

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

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