section 6: cell division and organisation

• What is the order of the cell cycle?

  Gap phase 1

  G1 check point

  Synthesis

  Gap phase 2

  G2 checkpoint

  M phase
• what happens during the m phase of the cel cycle?

  Cell division occurs during the M phase of the cell cycle, including mitosis and cytokinesis
• What happens during gap phase one of the cell cycle?

  Cell grows and new organelles and proteins are made
• What happens during the g1 checkpoint?

  The cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering s phase.
• what happens during the s phase?

  DNA replication
• What happens during gap phase 2?

  The cell keeps growing and more proteins for cell division are made.
• What happens in the g2 checkpoint?

  The cell checks whether all the DNA has bee nreplicated without any damage. If it has, the cell can enter mitosis
• what happens during the m phase?

  Mitosis and cytokinesis
• What happens during the interphase?

  The cell carries out normal functions, but also prepares to divie. DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so that it has spare, and the cell's ATP content is increased.
• what are the two types of cell division?

  Mitosis and meiosis.
• what is mitosis used for?

  Cell division and growth, in addition to tissue repair and asexual reproduction.
• How many cells are produced by mitosis?

  two genetically identical cells
• How many cells are needed in mitosis?

  One cell.
• What are chromatids joined by in mitosis?

  Centromere
• Why are there two chromatids in one chromosome?

  The cell made an identical copy of one during interphase.
• what happens in the prophase of mitosis?

  Chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle fibers begin to form.
• what happens in the metaphase of mitosis?

  The chromosomes line up along the equator of the cell, and become attached to the spindle via their centromere.
• What happens at the metaphase checkpoint?

  the cell checks that all the chromosomes are attached to the spindle before mitosis can continue.
• What happens during the anaphase of mitosis?

  The centromeres divide, separating each pair of chromatids. The spindles contract, pulling chromatids to opposing ends of the cell.
• what happens during the telophase of mitosis?

  The chromatids reach the opposite poles on the spindle. they uncoil and become long and thin again, now called chromosomes again. A nuclear envelope forms around each group of chromosomes so that there are now two nuclei.
• What happens during cytokinesis?

  The cytoplasm divides. in animal cells, a cleavage furrow forms to divide the cell membrane.
• what happens during sexual reproduction?

  Two gametes join together at fertilisation to form a zygote, which divides and develops into a new organisms
• What are the gametes of humans?

  Sperm for males and eggs for females.
• What is the diploid number of normal body cells?

  2 n
• what is the result of having a diploid number of 2n ?

  Each cell contains two of each chromosome, one from the mother and one from the father.
• What are the similarities and differences of homologous chromosomes?

  Same size and gene, with a possible different version of genes called an Allele.
• what is the haploid number of gametes?

  N
• What is the result of having N number of chromosomes for haploids?

  There is only one copy each chromosome. At fertilisation, a haploid sperm fuses with a haploid egg which makes a cell with the normal diploid (2n) number. This produces a zygote.
• what is mitosis?

  Cell division process, that produces two idential daughter cell from one parent.
• What is meiosis?

  Meiosis is a type of cell division that produces gametes (sex cells) with half the number of chromosomes as the parent cell.
• How many parent cells are needed in meiosis?

  One parent cell is needed in meiosis.
• What is the product of meiosis?

  Gametes, that are genetically unique
• Why are the products of meiosis genetically unique?

  Crossing over and independent assortment during meiosis create genetic variation.
• what is the first step in meiosis?

  The interphase
• What happens in the first prophase of meiosis?

  Chromosomes condense and pair up. Crossing over occurs. Centrioles move to opposite sides of the cell, forming spindle fibres. The nuclear envelope begins to break down
• what happens during metaphase 1 in meiosis?

  Homologous chromosomes line up at the equator of the cell, attaching to the spindle fibres.
• What happens in anaphase 1 of meiosis?

  Homologous chromosomes separate and move to opposite poles of the cell.
• What happens in telophase 1 of meiosis?

  A nuclear envelope forms around each group of chromosomes. Cytokinesis occurs and two haploid daughter cells are produced.
• What is the difference in the second meiosis?

  Crossing over and recombination occur in the second meiosis.
• What happens in the second anaphase??

  The sister chromatids are seperated so that each new daughter cell can inherit one chromatid from each chromosome.