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

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

These chromosomes Have not replicated These chromosomes have replicated

Haploid and Diploid Cells Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis Haploid and Diploid Cells An organism produces gametes to maintain the same number of chromosomes from generation to generation. 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.

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

Human meiosis reduces the cell from 46 to 23 chromosomes. Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis Stages of Meiosis Involves two consecutive cell divisions called Meiosis I and Meiosis II 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.

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

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

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

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

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

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

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

Meiosis II – Anaphase II Chapter 10 Sexual Reproduction and Genetics 10.1 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

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

Meiosis II - Cytokinesis Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis Meiosis II - Cytokinesis Cytokinesis results in four haploid cells, each with n number of chromosomes. The 4 daughter cells are genetically unique. Cytokinesis

The Importance of Meiosis Chapter 10 Sexual Reproduction and Genetics 10.1 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

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

This process is aided by wind & animals 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 vs. Asexual Reproduction Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis 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. 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 vs. Asexual Reproduction Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis Sexual vs. Asexual Reproduction Sexual reproduction The organism inherits different genetic info from each parent. The new individual is genetically unique from its parents. Advantages: More genetic variation means possible survival in a changing environment. Disadvantages: Slower, 2 parents & mating required.

In rabbits, gray fur (G) is dominant to black Chapter 10 Sexual Reproduction and Genetics 10.2 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? 1:1 1:2:1 2:1 3:1 A B C D FQ 7

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

Two genes on the same chromosome may become separated during meiosis. Chapter 10 Sexual Reproduction and Genetics 10.3 Formative Questions Two genes on the same chromosome may become separated during meiosis. true false A B FQ 9

What is the term for an organism that has one Chapter 10 Sexual Reproduction and Genetics 10.3 Formative Questions What is the term for an organism that has one or more sets of extra chromosomes in its cells? diploid gamete hybrid polyploid A B C D FQ 10

How many chromosomes would a cell have Chapter 10 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 10 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 10 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 10 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 10 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 10 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

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

1/4 1/2 1 For human eye color, brown is dominant and Chapter 10 Sexual Reproduction and Genetics Standardized Test Practice 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? 1/4 1/2 1 A B C D STP 5