Mitosis + Meiosis

• A pair chromosome contains two identical strands called chromatids, which are joined at the centromere
• Chromatids are formed during DNA replication, in preparation for cell division (to grow, reproduce, repair)
• Transcription: The process of making an mRNA copy from a DNA strand
• Protein synthesis:
• Transcription and Translation are
• Transcription:


  1.  DNA unwinds with the help of enzymes like RNA polymerase

  2. As it unwinds, the RNA polymerase moves along the strand of exposed gene (template strand) and joins together RNA nucleotides in a sequence, forming mRNA (mRNA bases are complementary to DNA bases)

  3. The RNA polymerase detaches from the mRNA and the DNA winds back together
• Translation 1. The mRNA leaves the nucleus and joins the Ribosome

  2. The nitrogen bases of the mRNA are arranged in codons (sets of 3 bases)

  3. Each codon codes for a specific amino acid

  4. tRNA (transfer RNA) transfers the amino acid to the Ribosome to be processed, where it will join a chain of amino acids that eventually form a protein
• mRNA contains ribose sugar (unlike DNA which contains deoxygenated ribose sugar)
• mRNA contains 4 nitrogen bases: cytosine (C), guanine (G), adenine (A), uracil (U) 
• The bases of mRNA are complementary to bases of DNA
• label

  A) DNA molecule

  B) template strand

  C) transcription

  D) mRNA

  E) translation

  F) protein

  G) codon

  H) amino acid

  
• label

  A) cell

  B) nucleus

  C) chromosome

  D) DNA

  E) Genes

  F) base pairs

  
• mRNA is smaller than DNA, therefore can leave nucleus and enter Ribosome
• there are 20 amino acids used to make protein
• Mitosis: process of cell division that results in genetically identical daughter cells
• Mitosis allows for cell growth and repair
• Cell cycle has two phases; interphase and mitotic phase
• Stages of mitosis: prophase – metaphase – anaphase – telophase – cytokinesis – interphase 
• Prophase is when chromatin condenses into visible chromosomes (chromosomes appear), the nuclear membrane disappears, and the spindle forms between the centrioles
• Metaphase is when chromosomes line up in a single line across the centre of the cell
• Anaphase is when each pair of chromatids separate at the centromere and each chromatid (now chromosome) moves to the opposite pole
• Telophase is when new nuclei form around the separated sets of chromosomes, the cytoplasm divides by cytokinesis, and the cells are now ready to divide again
• Cytokinesis is when the cytoplasm divides and two daughter cells are produced

   
• Interphase is where the cell grows and replicates its DNA
• Mitosis forms somatic cells, while meiosis forms gamete cells
• during anaphase, the spindles pull the chromosomes apart
• haploid: containing one complete

  set of chromosomes in each

  cell; an example is gametes
• haploid: a cell that contains only one set of chromosomes
• diploid: cell with 2 complete sets of chromosomes, one from each parent
• In meiosis, cells go through cell division twice
• after the first round of division, 2 haploid cells with 2 sets of chromosomes are produced, then the cells go through another round of division to produce 4 gametes, each with only 1 set of chromosomes