Ch 11 Sexual Reproduction and Meiosis

Reorder

Reorder the phases of mitosis

• Prophase

• Metaphase

• Anaphase

• Telophase

1

2

3

4

• 1
• 2
• 3
• 4

Match

Match the following

Nuclear envelope disappears; spindle fibers begin to form; chromatin condenses into chromosomes

Chromosomes line up in the middle of the cell

Sister chromatids are pulled away from each other

Nuclear envelope begins to form; spindle fibers fall apart; chromosomes relax into chromatin

• Nuclear envelope disappears; spindle fibers begin to form; chromatin condenses into chromosomes

• Chromosomes line up in the middle of the cell

• Sister chromatids are pulled away from each other

• Nuclear envelope begins to form; spindle fibers fall apart; chromosomes relax into chromatin

Multiple Choice

Which of the following does NOT accurately describe homologous pairs of chromosomes?

• Homologous chromosomes code for the same genes and may have different alleles.

• Homologous pairs contain one chromosome inherited from the father and one from the mother.

• Homologous pairs contain one original chromosome and one replicated copy.

• Human cells contain 23 pairs of homologous chromosomes.

Open Ended

What kind of cells would need to be HAPLOID and why.

Home

Open in new tab

Copy link

Multiple Choice

State the ploidy level and the number of chromosomes shown in the figure.

• n=8

• 2n=8

• n=16

• 2n=16

Multiple Choice

If a diploid cell contains 10 chromosomes, choose the correct ploidy level and the number of chromosomes in the cell after;

• Mitosis: 2n=20

  Meiosis: n=10

• Mitosis: 2n=10

  Meiosis: n=5

• Mitosis: n=20

  Meiosis: 2n=10

• Mitosis: n=10

  Meiosis: 2n=5

​LE Lateral element
TF Transverse Filament
CE Central Element

​Important Terminologies

​ Sister chromatids: the identical copies (chromatids) formed by the DNA replication of a chromosome

​ Homologous chromosomes:Two chromosomes in a pair – normally one inherited from the mother and one from the father.

The chromosomes in a homologous pair each have the same genes in the same order, but there may be variation between them, resulting in different alleles.

​/tetrad

​ Bivalent/ tetrad:  Each pair of homologous chromosomes consists of four chromatids which are undergoing synapsis. 

​Chiasma: a point at which paired chromosomes undergo crossing over and exchange of genetic material occur between the strands.

Synapsis
The pairing and physical connection of one duplicated chromosome to its homolog during Prophase I

Crossing Over:
the exchange of genetic
material between non-sister
chromatids of homologous
chromosomes during meiosis

Home

Open in new tab

Copy link

Law of Segregation:

Happens during Metaphase I

What Do I
Need To
Know?

Home

Open in new tab

Copy link

o During independent

assortment,
homologous
chromosome are
divided in half to form
haploid cells randomly.

o Happens during

Metaphase I.

What Do I
Need To
Know?

Multiple Choice

Which of Mendel's laws states that Chromosomes are distributed to gametes independent of one another?

• Law of Dominance

• Law of Segregation

• Law of Independent Assortment

Multiple Choice

Which of Mendel's laws states that alleles are separated during meiosis?

• Law of Dominance

• Law of Segregation

• Law of Independent Assortment

Multiple Choice

Which of the following best explains why meiosis results in greater genetic diversity than mitosis?

• After meiosis, daughter cells are diploid and have twice as much genetic material, which can be divided in many more possible combinations.

• After meiosis, haploid daughter cells are fertilized, which doubles their number of chromosomes and increases the number of possible genes.

• During meiosis, chromosomes assort themselves independently of each other, which allows for more different possible combinations of chromosomes.

• During meiosis, more daughter cells are produced, which increases the likelihood that fertilization will occur.

Multiple Choice

This diagram shows a diploid cell with two pairs of homologous chromosomes.

Due to independent assortment, what is the possible genetic make-up of gametes produced by this organism?

• SsTt

• Ss, Tt

• S, s, T, t

• ST, St, sT, st

​Meiosis and Genetic Variation

​Sources of Genetic Variation:

• crossing over - exchange of genetic information

• independent assortment of chromosomes

• segregation of alleles​

• random fertilization​

Home

Open in new tab

Copy link

Home

Open in new tab

Copy link

​

Match

Match the correct statements with the corresponding type of cell division.

​

• Mitosis is defined as

• Meiosis
  type of cell?

• Mitosis
  type of cell?

• Meiosis
  End result

• Mitosis
  End result

the division of the replicated contents of the nucleus of somatic cells

Haploid Cells

diploid cells

4 different daughters' cells

2 identical daughters' cells

• the division of the replicated contents of the nucleus of somatic cells

• Haploid Cells

• diploid cells

• 4 different daughters' cells

• 2 identical daughters' cells

General Rules​
Mitosis vs Meiosis I: different chromosomal behaviour but same number of chromosomes.

Mitosis vs Meiosis II: similar chromosomal behaviour but different number of chromosomes (chromosome number is half/n in meiosis II)

Meiosis I vs Meiosis II:
different chromosomal behaviour and number of chromosomes

(chromosome number is half/n in meiosis II)

​Prophase vs Prophase I vs Prophase II

Similarities

• Chromatin / chromosome shortens, thicken and condense

• Nuclear membrane & nucleolus disintegrate / disappear

• A pair of sister chromatids attached together at centromere

• Centrosome migrate to opposite poles / spindle fiber begins to form

• No synapsis

• No crossing over

• Chromosome number is diploid.

• Synapsis (Homologous chromosomes pair up)

• Crossing over occurs at chiasmata.

• Chromosome number is diploid

• No synapsis (Sister chromatids line up)

• No crossing over

• Chromosome number is haploid

​2n=4

​2n=4

​n=2

​Differences

Multiple Choice

State the phase and the chromosomal event shown in the figure.

• Prophase: no synapsis and crossing over between non-sister chromatids

• Prophase I: synapsis and crossing over occurs between non-sister chromatids

• Prophase II: no synapsis and crossing over between non-sister chromatids

• Prophase II: synapsis and crossing over occurs between non-sister chromatids

Multiple Choice

State the phase and the chromosomal number shown in the figure.

• Prophase, n=6

• Prophase, 2n=6

• Prophase I, n=6

• Prophase I, 2n=6

• Prophase II, n=6

​Metaphase vs Metaphase I vs Metaphase II

• Chromosomes align at metaphase plate

• Homologous chromosomes align at metaphase plate (Chromosomes line up in pairs)

• Chromosomes align at metaphase plate (same chromosomal behaviour as Metaphase but chromosomal number is halved)

​2n=4

​2n=4

Metaphase

Metaphase I

Metaphase II

​n=2

Multiple Choice

A diploid cell has 6 chromosomes. Determine the phase and chromosomal behaviour of the cell as shown in the figure.

• Metaphase: chromosomes align at metaphase plate

• Metaphase I: Homologous chromosomes align at metaphase plate

• Metaphase II: Chromosomes align at metaphase plate

• Metaphase II: Homologous chromosomes align at metaphase plate

​Anaphase vs Anaphase I vs Anaphase II

• Sister chromatids separate and move to the opposite poles

• Centromeres split

• Homologous chromosome separate and move to the opposite poles

• Centromeres do not split

• Sister chromatids separate and move to the opposite poles

• Centromeres split

  (same chromosomal behaviour as Anaphase but chromosomal number is halved)

Anaphase

Anaphase I

Anaphase II

Multiple Choice

State the phase and the chromosomal behaviour shown in the figure.

• Anaphase: Sister chromatids separate & move to the opposite poles

• Anaphase: Homologous chromosomes separate & move to the opposite poles

• Anaphase I: Sister chromatids separate & move to the opposite poles

• Anaphase I: Homologous chromosomes separate & move to the opposite poles

• Anaphase II: Sister chromatids separate & move to the opposite pol

​Telophase vs Telophase I vs Telophase II

• Chromosomes arrive at the opposite poles (each chromosomes consist of 1 chromatids)

• Each pair of homologous chromosomes arrive at the opposite poles.

• Chromosomes arrive at the opposite poles (each chromosomes consist of 1 chromatids)

  *same chromosomal behaviour as Telophase but chromosomal number is halved

Telophase

Telophase I

Telophase II

Similarities

• Nuclear membrane & nucleolus reappear

• Spindle fibre disintegrates.

Multiple Choice

Name the phase shown in the figure. What is the ploidy level and chromosomal number in each cell at the end of this phase?

• Telophase. n=3

• Telophase. 2n=6

• Telophase I. n=3

• Telophase I. 2n=6

• Telophase II. n=3

Multiple Choice

Cells and the organisms they make up reproduce through cell division. Some organisms reproduce through mitosis, while others reproduce through meiosis and fertilization. What advantage does meiosis give to organisms that reproduce sexually?

• Meiosis ensures that offspring inherit genes from their parents.

• Meiosis ensures that offspring will not inherit any genetic disorders.

• Meiosis ensures that offspring are genetically different from their parents.

• Meiosis ensures that offspring will have identical phenotypes to their parents.

Multiple Choice

Some organisms are able to reproduce asexually through mitosis, while cells of organisms that reproduce sexually will undergo meiosis to produce gametes. Which process do you predict would be most beneficial to a species during drastic change in environmental conditions?

• Meiosis; it results in more daughter cells, which increases the population of the species.

• Meiosis; it results in more genetic variation, which would help ensure the species will survive.

• Mitosis; it results in more genetic mutations, which may be advantageous to the species.

• Mitosis; it results in more offspring in a short time, which increases the odds that some will survive.

Home

Open in new tab

Copy link

Categorize

Options (19)

Asexual division

Cell division for growth and repair

Results in two identical daughter cells

Occurs in somatic cells

Consists of prophase, metaphase, anaphase, and telophase

Chromosomes line up in the center of the cell during metaphase

Reduction division

Results in two haploid daughter cells

Consists of prophase I, metaphase I, anaphase I, and telophase I

Crossing over occurs during prophase I

Homologus chromosomes are separated during Anaphase I

Results in four haploid daughter cells

Occurs in reproductive cells

Consists of prophase II, metaphase II, anaphase II, and telophase II

Sister Chromatids are separated during Anaphase II

Similar to mitosis

Sexual division

Creates Gametes

Independant assortment occurs to ensure random assortment of parental chromosomes

Organize these options into the right categories

Mitosis

Meiosis 1

Meiosis 2

Meiosis overview