Cell division, cell diversity and cellular organisation - Module 2

Acrosome

An organelle found in the head of sperm cells which is specialised to digest the outer coating of an egg cell during fertilisation.

Anaphase

The third stage in mitosis where the chromosomes are pulled apart to the poles of the cell by the spindle fibres.

Anaphase 1

The third stage of meiosis where the chromosomes that make up the bivalent are pulled apart to the poles of the cell by the spindle fibres.

Anaphase 2

The seventh stage of meiosis where the chromatids are pulled apart to opposite poles of the cell.

Anucleate

A type of cell which does not have a nucleus.

Asexual reproduction

The production of genetically identtical offspring from one parent through the process of mitosis.

Bivalent

A pair of homologous chromosomes.

Ciliated epithelium

A type of epithelium which has many fine protrusions known as cilia and is specialised for sweeping dirt and debris out of the body.

Crossing over

The exchange of genetic material between two chromosomes in a bivalent.

Cytokinesis

The division of the cytoplasm at the end of mitosis to produce two new daughter cells.

Differentiation

The process where a cell develops certain features so that it is specialised to carry out a certain function.

Diploid

Cells with two copies of each chromosome.

Erythrocyte

An anucleate cell specialised to carry oxygen from the lungs around the body (commonly referred to as a red blood cell).

G 1 (gap 1) checkpoint

The first checkpoint in the cell cycle which occurs just before the end of G 1 phase and commits the cell to division under favourable conditions.

G 1 (Gap 1) phase

The first growth phase in interphase where the cell synthesises proteins and RNA, duplicates its organelles and increases in size before DNA replication in S phase.

G 2 (gap 2) checkpoint

The second checkpoint in the cell cycle which occurs at the end of G 2 phase and checks that the DNA was correctly replicated during S phase before the cell enters mitosis.

G 2 (Gap 2) phase

The second growth phase of interphase where the cell continues to increase in size and synthesize biomolecules.

Gametes

Sex cells that have a haploid nucleus and are produced through meioisis.

Gene loci

The location of a gene on a chromosome.

Guard cells

A type of cell usually found in pairs that is specialised to control the opening and closing of stomata.

Haploid

Cells with only one copy of each chromosome.

Homologous chromosomes

Two chromosomes with similar gene loci but different alleles, one inherited from each parent.

Independent assortment

A source of variation in meiosis where the bivalent chromosomes can line up either way around on the metaphase plate.

Interphase

The largest part of the cell cycle where cells spend most of their time growing, synthesising biomolecules and preparing for mitosis.

M (Metaphase) checkpoint

The checkpoint occurring at the end of metaphase during mitosis which ensures all of the chromosomes have correctly attached to the spindle fibres and aligned at the metaphase plate.

Meiosis

A type of cell division used to produce gametes that produces four genetically different haploid daughter cells from one parent cell.

Meristematic tissue

A type of plant tissue which contains stem cells and is usually found in the growing regions of the plant.

Metaphase

The second stage in mitosis where the chromosomes attach to the spindle fibres and align in the centre of the cell along the metaphase plate.

Metaphase 1

The second stage of meiosis where the bivalent chromosomes align along the metaphase plate and independent assortment occurs.

Metaphase 2

The sixth stage of meiosis where the recombinant chromosomes align on the metaphase plate.

Mitosis

The division of a cell to produce two genetically identical daughter cells.

Multipotent

A type of stem cell which has the ability to differentiate into any cell type within a certain tissue in the body.

Neutrophil

A type of white blood cell with a multi-lobed nucleus which is specialised to engulf and destroy pathogens.

Organ

A group of specialised tissues working together to carry out a specific function.

Organ system

A group of specialised organs working together to carry out a specific function.

Palisade cell

A type of cell found in the leaves of plants which contains many chloroplasts and is specialised to carry out photosynthesis.

Phloem

A tissue found in plants which is specialised for the transport of assimilates from their site of production to different parts of the plant where they are needed.

Pluripotent stem cell

A type of stem cell which has the ability to differentiate into any cell type in the body.

Prophase

The first stage in mitosis where the nuclear envelope breaks down, the centrosomes move to opposite poles of the cell, the mitotic spindle begins to form and the chromosomes condense.

Prophase 1

The first stage of meiosis where the nuclear envelope breaks down, the spindle fibres form and the chromosomes condense and form bivalents. This is the stage of meiosis where crossing over occurs.

Prophase 2

The fifth stage of meiosis where the nuclear envelope breaks down, the spindle fibres form and the chromosomes condense.

Recombinant chromosomes

The chromosomes produced by the crossing over and exchange of genes during metaphase 1.

Root hair cell

A type of cell that is found in the roots of cells which has a large surface area and is specialised for the uptake of water and ions from the soil.

S (synthesis) phase

The second phase in the cell cycle where the DNA in the cell is replicated.

Somatic cells

Any cells that make up an organism excluding sex cells (sperm and egg cells).

Sperm cell

The male gamete which contains a long tail, an acrosome and lots of mitochondria and is specialised to fertilise an egg cell.

Squamous epithelium

A type of epithelium which is only one cell thick and is specialised for rapid diffusion.

Stem cell

A type of undifferentiated cell which has the ability to divide many times and differentiate into many different cell types.

Stomata

Small openings in the leaves or stem of a plant that can be opened or closed by guard cells in response to varying conditions.

Telophase

The final stage of mitosis where new nuclear envelopes begin to form around the separated sets of chromosomes.

Telophase 1

The fourth stage of meiosis where the nuclear envelopes reform around the separated chromosomes and they uncoil.

Telophase 2

The final stage in meiosis where the nuclear envelopes reform around the separated chromatids (now called chromosomes) and they uncoil.

Tissue

A group of specialised cells working together to carry out a specific function.

Totipotent stem cell

A type of stem cell which has the ability to differentiate into any type of cell in the body or in the placenta.

Xylem

A tissue found in plants which is specialised for the transport of water and dissolved minerals up the plant.