Cell Division Day 3: Meiosis

Types of Cell Division

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Hotspot

Which section of the cell cycle could be labeled as interphase?

Categorize

Options (11)

Kidney Cell

Egg Cell

Liver Cell

Brain Cell

Zygote

Stomach Cell

Fertilized Egg Cell

Sperm Cell

Gamete

Sex Cell

Somatic Cell

How many chromosomes are found in the following human cells?

46

23

Multiple Choice

Chromosomes line up at the equator of the cell

Spindle fibers extend from the centrioles to the middle of the chromosomes

• Prophase

• Metaphase

• Anaphase

• Interphase

Multiple Choice

95% of the cells life cycle

Stage where DNA is copied

• Interphase

• Metaphase

• Telophase

• Prophase

Multiple Choice

One difference between cell division in plant and animal cells is during cytokinesis plant cells have —

• cleavage

• a cell plate

• chromosomes

• centrioles

Multiple Choice

Nuclear membrane breaks down, spindle fibers form describes:

• Prophase

• Anaphase

• Metaphase

• Telophase

Sexual Reproduction, What is it?

Involves 2 parents that will produce offspring that are genetically distinct from each parent.
Sex Cells/Gametes are needed to reproduce sexually
Males=Sperm
Females=Egg/Ovum
When the two cells are fused together ( Fertilization) the result is called a zygote

Multiple Choice

Diagrams A through E represent five stages in a simplified model of sexual reproduction and development. At which stage is fertilization occurring?

• A

• B

• C

• E

Some Important Vocab....

Karyotype: A picture of a person’s chromosomes

There are 22 numbered pairs of chromosomes called Autosomes; these code for other traits (not sex)

The 23rd pair of chromosomes are the sex chromosomes and they determine an individual’s sex.

Homologous Chromosomes make up a pair of Autosomes; One chromosome of each homologous pair comes from the Father and one comes from the Mother. Homologous Chromosome Pairs are the same size, same shape, and carry the same genes but, the alleles (choices/version) for each trait may not be the same (example: Dad's codes for brown eyes and mom's codes for blue eyes, but both are still coding for eye color.)

So, Meiosis is different than Mitosis?

Where Mitosis creates offspring that are identical to the parent, Meiosis allows for GENETIC VARIATION. Once the gametes combine, it results in offspring that are different from the parents and other siblings.
The ONLY Exception: identical twins Genetic Variation increases the chances that a population and/or species has of survival

EX: Some individuals may have inherited a trait making them resistant to certain diseases or tolerant of certain conditions which help them to better survive in changing conditions

Clutch of baby bull snakes, all full blood siblings, with varying colors

So, Meiosis is different than Mitosis?

Mitosis: Occurs in Somatic Cells, is Asexual Reproduction, Undergoes ONE round of division, makes TWO Identical Daughter Cells, goes from Diploid Parent Cells to Diploid Daughter Cells

Meiosis: ONLY occurs in gametes, is Sexual Reproduction, Undergoes TWO rounds of division, makes FOUR Genetically Distinct Daughter Cells, goes from Diploid Parent Cells to Haploid Daughter Cells.

Labelling

The process on the left is:
The process on the right is:

Drag labels to their correct position on the image

Mitosis

Meiosis

Meiosis Phases

Meiosis is called reduction division because the
chromosomes replicate once (during interphase) but
2 cell divisions follow (Meiosis I & Meiosis II) to
reduce the number of chromosomes from diploid to haploid

Copy this:
Meiosis I Separates Homologous Chromosomes

Meiosis II Separates Sister Chromatids

(kinda like mitosis but makes 4 haploids instead of 2 diploids)

Multiple Choice

A. What does the picture below show?

B. Why is this important?

• A. crossing over

  B. increases variation/diversity

• A. crossing over

  B. decreases variation/diversity

• A. nondisjunction

  B. increases variation/diversity

• A. nondisjunction

  B. decreases variation/diversity

Multiple Choice

Which of the following best describes independent assortment?

• The exchange of genetic material between non-sister chromatids

• The random separation of sister chromatids

• The random orientation of homologous chromosomes during metaphase I

• The duplication of chromosomes before cell division

Multiple Choice

Describe the process of anaphase I in meiosis.

• Sister chromatids separate and move to opposite poles of the cell.

• The cell divides into two daughter cells.

• The chromosomes replicate.

• Homologous chromosomes separate and move to opposite poles of the cell.

Multiple Choice

Which event does NOT occur during Telophase I?

• Decondensation of chromosomes.

• Formation of two new nuclei.

• Separation of sister chromatids.

• Cytokinesis begins.

Multiple Choice

What process is being represented in this diagram?

• asexual reproduction

• mitosis

• meiosis

• DNA replication

Dropdown

Which stage of meiosis is where sister chromatids are separated? ​

Select answer

Which stage of meiosis is where homologous chromosomes are separated? ​

Select answer

Which stage of meiosis and which phase is where synapsis occurs as well as crossing over? ​

Select answer

Which stage of meiosis and which phase is where homologous chromosomes pair up? ​

Select answer

​ Which stage of meiosis is most similar to mitosis ​

Select answer

Dropdown

What phenomenon is responsible for creating more genetic diversity ​

Select answer

What forms when homologous chromosomes pair up during synapsis? ​

Select answer

Labelling

Label the stages of Meiosis

Drag labels to their correct position on the image

Anaphase 1

Prophase 1

Metaphase 1

Anaphase 2

Prophase 2

Telophase 1

Telophase 2

Metaphase 2

Meiosis Increases Genetic Variation?

Yes, for a few reasons:
1. Independent Assortment: Each pair of chromosomes can be arranged in two ways when they pair up at the start of meiosis, mom on the "left" dad on the "right" or vice versa. The result= 8 million different possibilities PER CELL

2. Crossing Over: When homologous chromosomes form tetrads, the strands of the chromatids can twist around each other and may exchange segments.

3. Genetic Recombination:
Recombine means to combine again or differently.
When the sperm fertilizes the egg, the chromosomes are recombined, which means the diploid chromosome number has been restored in the zygote. However, there may be new combinations due to the variations that were passed down from mother and father.

*FACT: There are 64 TRILLION different possibilities when a sperm and egg cell unite