Meiosis

Meiosis

HOMEWORK

Meiosis Hw due
1/16/24

Objective

◦ B.8A

◦ Investigate how variation is increased

due to the process of meiosis

Agenda

◦ Do now (5)

◦ Quizziz (35)

◦ Exit ticket (5)

Purpose

 The purpose of meiosis is to create

gametes (sex cells; sperm & egg) through
cell division

Multiple Choice

What is the purpose of meiosis?

• The purpose of meiosis is to produce gametes for sexual reproduction.
• To produce identical daughter cells for growth.
• To facilitate cell division in prokaryotes.
• To repair damaged tissues in the body.

Process

 Meiosis is a process

where a single cell divides
twice to produce four
cells containing half the
original amount of genetic
information.

Multiple Choice

How many cells are produced at the end of meiosis

• 6
• 8
• 2
• 4

Gametes
A mature, haploid reproductive cell that is created due to
meiosis.

Male gamete = sperm

Female gamete = egg

Multiple Choice

What is the male gamete cell?

• Egg cell
• Pollen grain
• Zygote
• Sperm cell

Homologous
Chromosomes

a pair of chromosomes that are
similar in length as well as gene
and centromere position

Homo = the same

Draw

Draw your own homologous chromosomes.

Chromosome vs
Chromatid

A chromosome is a single structure
containing DNA, while a chromatid is
one of the two identical strands of a
replicated chromosome.

Putting it all together

Diploid

a cell containing two complete
sets of chromosomes, one from
each parent.

Di = two

Haploid

a cell containing a single set of
unpaired chromosomes.

Haploid = Half

The gametes (sperm and egg
cells) of an organism are haploid

Multiple Choice

What is the difference between diploid and haploid?

• Diploid has one set of chromosomes; haploid has two sets.
• Diploid and haploid both have the same number of chromosomes.
• Diploid is found in prokaryotes; haploid is found in eukaryotes.
• Diploid has two sets of chromosomes; haploid has one set.

Crossing Over

Crossing over is a cellular
process that occurs during
meiosis when homologous
chromosomes (one from each
parent) exchange DNA.

This increases genetic variation

Draw

Draw two chromosomes crossing over.

Meiosis happens twice

Prophase 1

• Crossing over
• During prophase I, chromosomes pair up and exchange genetic

material in a process called crossing over. This process creates
chromosomes with unique combinations of alleles.

Metaphase 1

• Chromosomes line up in the middle of the cell

Anaphase I

• microtubules pull the homologous pairs of chromosomes apart.

The sister chromatids remain attached at the centromere.

Telophase I

• two new cells are formed with a haploid number of

chromosomes.

Before moving on to the
second part..

Phases

 Meiosis II has four

phases: prophase II,
metaphase II, anaphase II,
and telophase II.

 Meiosis II produces four

daughter cells, each with
half the genetic material
of the original cell.

Meiosis happens twice

Prophase II

The chromosomes condense again, and the spindle apparatus
begins to form in each haploid cell.

Metaphase II

Chromosomes line up individually along the metaphase plate. The
spindle fibers attach to the centromeres of each sister chromatid.

Anaphase II

Microtubules pull the sister chromatids apart, moving them to
opposite sides of the cell

Telophase II

The nuclear membranes reform around the separated chromatids,
now called chromosomes. This results in four haploid daughter
cells, each genetically distinct.