inheritance (11)

• 46 chromosomes in humans = diploid
• 23 chromosomes in human gametes = haploid
• DNA makes up chromosomes and genes
• DNA structure:

  • double helix shape
  • sugar phosphate backbone
  • paired bases
  • held together by hydrogen bonds
• why doesnt ----- have a typical DNA structure?

  no equal number of bases

  not paired together

  no double helix shape
• messenger RNA = mRNA
• moving from DNA to mRNA:

  • DNA stuck in nucleus = too large to leave
  • mRNA used to carry base code to ribosomes in cytoplasm - travels from nucleus as is shorter
  • mRNA tells ribosomes what order to assemble amino acids in = decides what proteins are made + what characteristics
• changes to base sequence called mutations = differences in the protein
• DNA bases are :

  • A = adenine
  • T = thymine
  • C = cytosine
  • G = guanine
• mRNA bases are:

  • A = adenine
  • U = uracil
  • C = cytosine
  • G = guanine
• mRNA = messenger RNA
• rRNA = ribosome RNA
• tRNA = helps with proteinsynthesis
• DNA is made of nucleotides
• each nucleotides has one deoxyribose, one phosphate and 1 of 4 bases
• nucleotide in DNA:

  
• bases pairs in DNA:

  Adenine and Thymine pair

  Cytosine and Guanine pair
• each base in a pair has an equal percentage

  eg. 15% of Adenine = 15% of Thymine
• DNA has a sugar phosphate backbone
• bases are held together by hydrogen bonds
• DNA codes for the order of amino acids that must be put together to make a particular protein
• if the order of amino acids changes = the protein might be non-functional
• the order of amino acids is decided by the base sequence
• DNA bases: 3 bases is called a triplet
• mRNA bases: 3 bases is called a codon
• tRNA bases: 3 bases is called an anti-codon
• tRNA cannot go straight to DNA
• a row of codons should give the same sequence of amino acids as the corresponding DNA triplets
• 3 bases = 1 amino acid
• protein synthesis?

  the making of proteins using the DNA code
• 2 stages to protein synthesis:

  1 = transcription - DNA used to make mRNA - in the nucleus

  2 = translation - the code in the mRNA is used to put the amino acids into the right order + join the together at ribosomes
• RNA Polymerase is needed for transcription
• tRNA is needed for translation
• transcription: the process of copying the DNA into a single strand of RNA
• transcription:

  1 = DNA double helix is "unzipped" as the hydrogen bonds are broken between the complementary bases

  2 = RNA Polymerase moves along exposed DNA bases and as the complementary RNA nucleotides join to the DNA bases = joins the sugar phosphate backbone together

  3= the RNA Polymerase uses DNA as a template to give order of RAN nucleotides - RNA nucleotides are floating freely in the nucleus and cytoplasm

  4 = new mRNA is released from the RNA Polymerase and can move out of the nucleus and into the cytoplasm = and the DNA base join back together
• translation: the code in the mRNA is used to put amino acids into the right order and join amino acids together at ribosomes
• translation:

  1. Translation is the making a protein using the code in the mRNA
  2. the mRNA is in the cytoplasm and it goes to the ribosome
  3. while the mRNA is in the ribosomes, a tRNA with matching anti-codons lines up with the mRNA codon
  4. while he anti-codon and the codon are held together, the amino acid on the tRNA joins to the next tRNAs amino acids
  5. "empty" tRNAs are released into cytoplasm, and the ribosome keeps moving along the mRNA and more tRNAs move in, bringing their amino acids to join the new protein
• allele - a form of a gene

  • either recessive or dominant
• phenotype = looks
• genotype = the letters