Human body cells have 46 chromosomes
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Transcript of Human body cells have 46 chromosomes
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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 and Chromosome Number
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Homologous chromosomes
10.1 Meiosis
Sexual Reproduction and Genetics
Same length
Same centromere position
Carry genes that control the same inherited traits
Chapter 10
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Haploid and Diploid Cells
Human gametes contain 23 chromosomes.
Sexual Reproduction and Genetics
A cell with n chromosomes is called a haploid cell.
A cell that contains 2n chromosomes is called a diploid cell.
10.1 Meiosis
An organism produces gametes to maintain the same number of chromosomes from generation to generation.
Chapter 10
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Meiosis I
The sexual life cycle in animals involves meiosis.
Sexual Reproduction and Genetics
Meiosis produces gametes.
10.1 Meiosis
When gametes combine in fertilization, the number of chromosomes is restored.
Chapter 10
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Stages of Meiosis I
Reduces the chromosome number by half through the separation of homologous chromosomes
Sexual Reproduction and Genetics
Involves two consecutive cell divisions called meiosis I and meiosis II
10.1 Meiosis
Chapter 10
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Interphase
Chromosomes replicate.
Chromatin condenses.
Chapter 10
Interphase
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Prophase I
Pairing of homologous chromosomes occurs.
Each chromosome consists of two chromatids.
The nuclear envelope breaks down.
Spindles form.
Chapter 10
Prophase I
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Prophase I Crossing over produces exchange of genetic
information. Crossing over—chromosomal segments are
exchanged between a pair of homologous chromosomes.
Chapter 10
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Metaphase I
Chromosome centromeres attach to spindle fibers.
Homologous chromosomes line up at the equator.
Chapter 10
Metaphase I
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Anaphase I
Chapter 10
Anaphase I
Homologous chromosomes separate and moveto opposite poles of the cell.
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Meiosis I
Sexual Reproduction and Genetics
10.1 Meiosis
Telophase I
The spindles break down.
Chromosomes uncoil and form two nuclei.
The cell divides.
Chapter 10
Telophase I
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Meiosis II
Prophase II
Sexual Reproduction and Genetics
10.1 Meiosis
Chapter 10
A second set of phases beginsas the spindle apparatus forms and the chromosomes condense.
Prophase II
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Meiosis II
Metaphase II
Sexual Reproduction and Genetics
10.1 Meiosis
Chapter 10
A haploid number of chromosomesline up at the equator.
Metaphase II
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Meiosis II
Sexual Reproduction and Genetics
10.1 Meiosis
Anaphase II
Chapter 10
Anaphase II
The sister chromatids arepulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.
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Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Chapter 10
Telophase II
The chromosomes reach the poles, andthe nuclear membrane and nuclei reform.
Telophase II
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Meiosis II
Sexual Reproduction and Genetics
Cytokinesis results in four haploid cells, each with n number of chromosomes.
10.1 Meiosis
Chapter 10
Cytokinesis
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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
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Sexual Reproduction and Genetics
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.
10.1 Meiosis
Chapter 10
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Sexual Reproduction and Genetics
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.
10.1 Meiosis
Chapter 10
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1. A2. B3. C4. D
CDQ 1
0% 0%0%0%
A. #
B. x
C. r
D. n
Which symbol is used to represent the number of chromosomes in a gamete?
Sexual Reproduction and GeneticsChapter 10
Chapter Diagnostic Questions
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1. A2. B3. C4. D
FQ 3
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 10
10.1 Formative Questions
How does the number of chromosomes in gametes compare with the number of chromosomes in body cells?
A. Gametes have 1/4 the number of chromosomes.
B. Gametes have 1/2 the number of chromosomes.
C. Gametes have the same number of chromosomes.
D. Gametes have twice as many chromosomes.
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1. A2. B3. C4. D
FQ 4
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 10
10.1 Formative Questions
What type of organisms only reproduce asexually?
A. bacteria
B. protists
C. plants
D. simple animals
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1. A
2. B
FQ 9
Sexual Reproduction and GeneticsChapter 10
10.3 Formative Questions
Two genes on the same chromosome may become separated during meiosis.
A. true
B. false
0%0%
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1. A2. B3. C4. D
CAQ 1
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 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
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1. A2. B3. C4. D
CAQ 2
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 10
Chapter Assessment Questions
A. prophase I
B. interphase
C. anaphase I
D. anaphase II
Which stage of meiosis is illustrated?
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1. A2. B3. C4. D
CAQ 3
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 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.
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1. A2. B3. C4. D
Standardized Test Practice
STP 1
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Sexual Reproduction and GeneticsChapter 10
What is this process called?
A. fertilization
B. gamete formation
C. inheritance
D. reproduction
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1. A2. B3. C4. D
Standardized Test Practice
STP 2
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 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
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1. A2. B3. C4. D
Standardized Test Practice
STP 3
0% 0%0%0%
Sexual Reproduction and GeneticsChapter 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