meiosis and mitosis

• what happens in asexual reproduction?

  the offspring are genetically identical
• what happens in sexual reproduction

  offspring are a mix of its parents dna
• what are gametes?

  Sex cells or reproductive cells.
• what are haploid cells?

  Cells with 23 chromosomes.
• what are diploid cells

  a cell with 46 chromosomes
• what are homologous pairs

  two chromosomes with the same set of genes
• what are the two halves of a homologous pair

  one maternal chromosome and one paternal chromosome
• what type of cell does meiosis form?

  Gametes or haploid cells
• what happens before meiosis?

  Interphase
• what happens in interphase?

  Cell growth, DNA replication, and preparation for cell division.
• how many cell divisions in meiosis

  2
• what happens in meiosis one?

  one parent cell to two cells
• what happens in prophase 1?

  chromatids condense into chromosomes and the nuclear envelope breaks down. homologous chromosomes pair up and form bivalents
• what happens in Metaphase 1

  homologous chromosomes line up in the middle of the cell - equator
• what happens in anaphase one?

  spindle fibres pull the chromosome pairs apart
• what happens in telophase 1?

  the chromosomes decondense and a nuclear envelope reforms
• what happens in prophase 2?

  chromatin condense into 23 chromosomes made of two sister chromatids
• what happens in metaphase 2?

  spindle fibres attach to each of the chromosomes and line them up along the equator
• what happens in anaphase 2

  sister chromatids are pulled apart and towards the poles
• what happens in telophase 2?

  chromosomes recondense and a nuclear envelope is formed
• what does meiosis make

  4 daughter cells that are haploid
• what are the three ways genetic diversity occurs in meiosis

  crossing over, random segregation, random mutations and the fact they can line up in any order
• when does crossing over occur?

  prophase one
• when does random segregation happen?

  metaphase one - homologous chromosomes

  metaphase two - sister chromatids
• what is mitosis used for?

  Cell division and growth, replacing damaged and worn out cells
• what happens in phase one of the cell cycle?

  the cell grows in size

  makes copies of its DNA and organelles
• what happens in phase two of the cell cycle?

  the nucleus divides into two
• what happens in phase three of the cycle?

  entire cell splits into two copies
• why can't prokaryotes undergo the cell cycle?

  no nucleus
• what is the first phase of the cell cycle called?

  Interphase
• how many phases of interphase are there?

  Three
• what is the first phase of interphase?

  G1 phase
• what happens in G1?

  Cell growth, protein synthesis and preparation for DNA replication.
• what is the second phase of interphase called?

  S phase
• what happens in the S phase?

  DNA replication
• what is the third stage of interphase?

  G2
• what happens in G2?

  Cell grows some more and organelle synthesis occurs
• what is the G1 checkpoint for?

  Checks the cell is large enough and has the correct organelles for DNA replication

  Checks that there is no damaged DNA
• what is the G2 checkpoint for?

  checks that the DNA has replicated accuratley
• What is the G0 phase?

  when cells do not divide e.g specialised cells or cells that fail G1 checkpoint