DNA and the production of proteins

• What does DNA do


  carries genetic information.
• Where is DNA found

  In the chromosomes, which are found in the nucleus of most cells
• A Gene is a section of DNA which codes for a

  protein.
• A section of DNA is known as a gene
• Genes code for proteins

  • Proteins determine the

  characteristics of an organism e.g.

  flower or eye colour
• DNA is a double helix with the two

  strands of DNA running in

  opposite directions
• The two strands of DNA

  are held together by

  complementary base

  pairing between the

  bases on opposite

  strands.
• Chromosomes are made of DNA
• DNA is found in the nucleus and

  carries the genetic instructions to make proteins
• DNA is composed of units called nucleotides
• A nucleotide is a phosphate group, joined to a deoxyribose sugar and to one of 4 possible bases
• A-T G-C
• Each strand is made of four bases

  adenine (A), thymine (T),

  guanine (G) and cytosine (C)
• The strands are held together by complementary base

  pairing
• Adenine pairs with thymine, Cytosine pairs with guanine
• DNA is unique to an individual because the order of

  DNA bases is different in each person
• A T G C G C T A

  T A C G C G A T
• At actual size, a human cell's DNA totals about 3 meters in length.
• If DNA is stretched out, would form very thin thread, about 6 feet (2 meters) long.
• The instructions for protein synthesis are coded in

  DNA.
• Each gene acts as a set of instructions, for making a

  particular protein.
• To enable genes to code for proteins, the bases A, T,

  G and C get together (not in pairs but) in triplets.
• Each triplet of bases codes for one

  particular amino acid
• The order of the amino acids in the protein is

  determined by the sequence of the bases in

  the gene's DNA.
• Each protein is made up of large numbers of amino acid

  molecules
• WHAT IS RNA?

  Ribonucleic Acid
• RNA is similar to DNA with a few important

  differences

  -The sugar in the sugar-phosphate backbone is

  Ribose instead of Deoxyribose.

  -The base thymine is replaced by another base

  which pairs with adenine.
• RNA is single stranded
• mRNA is formed in the nucleus of the cell from

  one of the DNA strands present in the nucleus.
• A complementary copy of the DNA is made,

  this is called mRNA therefore acting as a messenger
• mRNA carries the complementary code from

  the nucleus to the ribosomes.
• Ribosomes attach to mRNA, using its instructions to assemble amino acids in the correct order to form a specific protein.
• At the ribosomes, proteins are made from

  chains of amino acids.
• Peptide bonds form between adjacent amino acids.
• The protein is assembled by the ribosome from amino

  acids.
• peptide bonds join

  amino acids together
• The code to make proteins is stored in DNA on

  genes in the nucleus
• mRNA carries a complementary copy of DNA from the nucleus to a ribosome