Mitosis And Meiosis

Front 1

Mitosis

Back 1

A single nucleus gives rise to two nuclei which are genetically identical to each other, and to the parent cell

How most eukaryotic organisms replace old cells and
grow new cells

Front 2

Stages of Mitosis

Back 2

1. Interphase
2.Prophase
3.Metaphase
4.Anaphase
5.Telophase

Front 3

Interphase

Back 3

During the S phase of
interphase, the nucleus
replicates its DNA and
centrosomes.

Front 4

Prophase

Back 4

The chromatin coils and supercoils,
become more and more compact,
condensing into visible chromosomes.
The chromosomes consist of identical,
paired sister chromatids.

Front 5

Prometaphase

Back 5

The nuclear envelope
breaks down. Kinetochore
microtubules appear and
connect the kinetochores to
the poles.

Front 6

Metaphase

Back 6

The centromeres become
aligned in a plane at
the cell’s equator.

Front 7

Anaphase

Back 7

The paired sister
chromatids separate,
and the new daughter
chromosomes begin to
move toward the poles.

Front 8

Telophase

Back 8

Daughter chromosomes reach the
poles. As telophase concludes, the
nuclear envelopes and nucleoli reform,
chromatin becomes diffuse,
and the cell again enters interphase.

Front 9

Asexual Reproduction

Back 9

Based on mitotic division of the nucleus.
• It may be a unicellular organism reproducing itself, or:
• Cells of multicellular organisms that break off to form a new individual
• The offspring are clones—genetically identical to the parent.

Front 10

Sexual Reproduction

Back 10

Sexual reproduction: the offspring are not identical to the parents.
Meiosis produces gametes that
differ genetically from the parents, and also from each other.

Front 11

Karyotype

Back 11

The number, shapes, and sizes of the chromosomes in a cell.

Individual chromosomes can be
recognized by length, position of centromere, and banding
patterns.

Front 12

Ploidy

Back 12

The number of homologous
sets of chromosomes in a cell

Front 13

Diploid

Back 13

One set of chromosomes from each parent

Fertilization: two haploid gametes (female egg and male sperm) fuse to form a diploid zygote; chromosome number =
2n

Front 14

Haploid

Back 14

The number of chromosomes in a
gamete (sperm or egg)

Front 15

Homologous chromosomes

Back 15

One chromosome from each parent. Both homologues carry genes which code for the same inherited characters.

Front 16

Functions of meiosis

Back 16

• Reduce chromosome number from diploid to haploid.
• Ensure that each product has a full set of chromosomes.
• Promote genetic diversity among the products.

Front 17

Tetrads

Back 17

A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.

Front 18

"Crossing Over"- Recombinant

Back 18

Pieces of DNA swapped at chiasmata during prophase to create an independent assortment where each gamete has different genetic composition from each other and parents

Front 19

Stages of Meiosis

Back 19

1. Meiosis I
2. Prophase I
3. Metaphase I
4. Anaphase I
5. Telophase I

6. Meiosis II
7. Metaphase II
8. Anaphase II
9. Telophase II

Front 20

Meiosis I

Back 20

Prophase I
Metaphase I
Anaphase I
Telophase I

Same steps as in mitosis.

• Nuclear envelope reaggregates;
followed by an interphase called
interkinesis.
• In other organisms, meiosis II begins
immediately.

Front 21

Differences between Meiosis II and Mitosis

Back 21

• DNA does not replicate before meiosis II.
• In meiosis II the sister chromatids may not be identical because of crossing over.
• The number of chromosomes at the equatorial plate in meiosis II is half the number of those in mitosis.

Front 22

Meiosis II

Back 22

End result is production of four (daughter) haploid cells from the two (sister) haploid cells produced in meiosis I.

Front 23

Apoptosis

Back 23

Genetically programmed cell
death. Two possible reasons:
• Cell is no longer needed, e.g., the connective tissue between the fingers of a fetus.
• Old cells may be prone to genetic damage that can lead to cancer; blood cells, epithelial cells die after days or weeks.

Recycle inner organelles-nucleus self destructs-organelles organized into packets-packets absorbed into neighbor cells and used

Front 24

Necrosis

Back 24

Necrosis—cell is damaged or starved for
oxygen or nutrients. The cell swells and
bursts.
• Cell contents are released to the extracellular environment. Can cause inflammation.
• Scabs are necrotic tissue.

Cell membrane ruptures, releases lysosomes that kill other cells, all inner contents wasted