Lecture 2.3 - Cell Division

Flashcards covering key vocabulary related to cell division processes in prokaryotes and eukaryotes, including definitions of important terms.

Chromatin

Combination of DNA and proteins that make up chromosomes

Chromosome

A tightly coiled form of the DNA-protein complex; in molecular biology, refers to a single DNA molecule and associated proteins.

Chromatid

Identical copies of the same chromosome, often referred to as sister chromatids.

Centromere

The location at which sister chromatids are most closely attached.

Binary fission

The method of cell division in prokaryotes, where a single parent cell divides into two daughter cells.

Mitosis

A process of cell division in eukaryotes that results in two genetically identical diploid daughter cells.

Meiosis

A process of cell division that reduces the number of chromosomes, producing four haploid gametes, allowing for sexual reproduction.

Diploid

Cells that contain two sets of homologous chromosomes; for humans, this is typically 46 chromosomes (23 pairs).

Haploid

Organisms that have only 1 set of chromosomes (1n)

Cell cycle

The series of phases that a cell goes through, including interphase and mitotic phases.

Cytokinesis

The division of the cytoplasm, resulting in two separate daughter cells after mitosis.

Cleavage furrow

The narrow groove formed by actin microfilaments during cytokinesis in animal cells.

Gametes

Sex cells produced by meiosis that have half the number of chromosomes as the parental cell.

Alleles

Different versions of a gene that exist on homologous chromosomes.

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis that increases genetic diversity.

Independent assortment

The distribution of chromosomes to daughter cells in meiosis that leads to genetic variation.

Endosymbiotic theory

The theory that explains the origins of mitochondria and chloroplasts within eukaryotic cells.

S phase

The part of interphase where DNA is replicated.

Interphase

The phase of the cell cycle where the cell grows and DNA is synthesized before mitosis.

Cell division

How cells reproduce (1 parent cell divides into 2 daughter cells)

In unicellular organisms cell division…

Reproduction

In multicellular organisms…

Simple cell division enables growth

Daughter cells

Genetically identical to parent cell and each other

Prokaryotes divide by…

Binary fission

Eukaryotes divide by…

Mitosis or meiosis

Three steps of binary fission

1. Copy genome

2. Increase cell size

3. Split in two daughter cells

Copy genome - Binary fission

• From one origin of replication, replicate DNA in both directions to produce 2 large circular chromosomes

• Tightly pack chromosomes with special proteins + supercoiling

Two different cell division processes

Mitosis and meiosis

Why does mitosis occur?

Typical cell division, growth and repair

Why does meiosis occur?

• Necessary for sexual reproduction

• Additional steps to avoid excess DNA and increase genetic variability of offspring

What occurs in interphase of the cell cycle?

G1, S, G2

Two sections in the cell cycle

Interphase and mitotic phase

What occurs in the mitotic phase of the cell cycle

Mitosis, cytokinesis

What happens during S phase of the cell cycle

Copy all DNA starting from many points of origin

How long does the cell cycle take

24 hours

How long does a cell stay in interphase for

~23 hours

How long does a cell stay in mitosis for?

<1 hour

In early stages of mitosis

Condense into tightly packed chromatin fibres wrapped around special proteins called histones

What happens in G1 of the cell cycle?

Cell growth, normal gene expression

What happens in G2 of the cell cycle?

Cell growth, duplicate organelles

What happens in mitosis?

Prophase, prometaphase, metaphase, anaphase, telophase

What happens in cytokinesis?

2 new cells divide

Name the phase

Interphase

Name the phase

Prophase

Name the phase

Prometaphase

Name the phase

Interphase

Name the phase

Prophase

Name the phase

Prometaphase

Name the phase

Metaphase

Name the phase

Metaphase

Name the phase

Anaphase

Name the phase

Anaphase

Name the phase

Telophase and cytokinesis

Name the phase

Telophase and cytokinesis

Actin microfilaments form…

A ring on inside of cell membrane, in middle of dividing cells → forms a narrow groove

Filaments are…

Drawn together, pinching the cell membrane together → separates cytoplasm into two identical daughter cells

What must be recreated between daughter cells

Plants cell walls

Which of the following correctly matches a phase of the cell cycle with its description

G1, follows cell division

Errors in the cell cycle…

Can lead to uncontrolled cell growth - can lead to cancer

Is cancer a disease of mitosis of meiosis?

Mitosis

How many chromosomes does humans have?

Humans have 46 chromosomes, organized into 23 pairs, including one pair of sex chromosomes. (n = 23, 2n = 46)

Alleles

Both chromosomes in a homologous pair have the same genes, just different versions of the genes

Haploid or diploid

Haploid

Haploid or diploid

Diploid

Name the molecule

Chromosome

Name the middle

Centromere

Name the arms

Chromatid

Sexual reproduction

fusion of two cells from different individuals

What would happen if you fused two diploid cells?

You would produce a tetraploid cell, which contains four sets of chromosomes.

Gametes

For sexual reproduction to be possible, organisms need to produce cells with half the number of chromosomes as the parental cell

Cell division - mitosis

Produces 2 genetically identical diploid cells (each has 2n chromosomes)

Cell division - meiosis

Produces 4 haploid cells with half the number of chromosomes as parent cell (each has 1n chromosome)

Process of diploid and haploid cells

1 diploid cell (2n chromosomes (each with 2 chromatids)) (Meiosis 1) → 2 haploid cells (1n chromosome (each with 2 chromatids)) (start of meiosis 2) → 4 haploid cells (1n chromosome (each with 1 chromatid)) (after meiosis 2)

Stages of meiosis

Prophase 1, metaphase 1,anaphase 1, telophase 1, cytokinesis, prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis.

Meiosis produces…

Much greater genetic diversity than mitosis

Independent assortment

New combinations

Crossing over

Mixing chromosomes

Advantage of genetic diversity

Provides greater flexibility to adapt to changes in the environment

Asexual reproduction creates…

Exact clones

Advantage of asexual reproduction

Good if species is well adapted to its environment but if environment changes it takes time to adapt

Sexual reproduction creates…

Different versions

Advantage of sexual reproduction

Some may be better adapted to various environments, so if environment changes, there are already well-suited versions

Asexual reproduction

• Produces 2 identical daughter cells (clones_

• Allows reproduction from a single cell

Is Asexual reproduction mitosis or meiosis

Mitosis, as it results in identical daughter cells.

Sexual reproduction

• Produces 4 haploid daughter cells (gametes), genetically different from parent and from each other

• Requires 2 organisms, each providing 1 haploid (male provides sperm, female provides egg)

Is sexual reproduction mitosis and meiosis

Meiosis

A human cell containing 22 autosomes and a Y chromosome is

A sperm

Name the type of sexual life cycle

Animal

Name the type of sexual life cycle

Plant

Name the type of sexual life cycle

Most fungi and some protists

Which of the cells are haploid?

1. Sex cell (gamete)

2. Skin cell

3. Muscle cell

Sex cell

Does mitochondria have its on DNA?

Yes

How does mitochondria divide?

Binary fission

Mitochondria in sexual reproduction

Inherited exclusively from the mother (mitochondria in sperm are destroyed by egg after fertilisation)

Analysis of mitochondrial DNA (mtDNA)…

Can help establishing maternal ancestry (and evolutionary history)