cell division, cell diversity and cellular organisation

• Asexual reproduction

  The production of genetically identical 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)
• G1 (gap 1) checkpoint

  The first checkpoint in the cell cycle which occurs just before the end of G1 phase and commits the cell to division under favourable conditions
• G1 (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
• G2 (gap 2) checkpoint

  The second checkpoint in the cell cycle which occurs at the end of G2 phase and checks that the DNA was correctly replicated during S phase before the cell enters mitosis
• G2 (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)