DNA structure

• DNA has a twisted-ladder shape that is caused by molecules called nucleotides

• A nucleotide is a molecule made of a nitrogen base, a sugar, and a phosphate group.

DNA structure

• The nitrogen bases bond and form the rungs of the ladder. There are four nitrogen bases: adenine (A), cytosine (C), thymine (T), and guanine (G).

•  A and T always bond together. C and G always bond together.

DNA replication

• Replication is the process of copying a DNA molecule to make another DNA molecule

• The strands separate in many places. The nitrogen bases are exposed.

• New nucleotides move into place and form new nitrogen base pair

• This produces two identical strands of DNA

Making Proteins

• Proteins are important for every cellular process

• Most genes contain instructions for making proteins

• Proteins are made with the help of ribonucleic acid.

The Role of RNA in Making Proteins

• Ribonucleic acid (RNA) is a type of nucleic acid that carries the code for making proteins from the nucleus to the cytoplasm.

• RNA also carries amino acids around inside a cell.

• RNA forms a part of ribosomes.

Types of RNA

• Messenger RNA (mRNA)

• Transfer RNA (tRNA)

• Ribosomal RNA (rRNA)

• They work together to make proteins.

Transcription

•  Transcription is the process of making mRNA from DNA.

• mRNA nucleotides pair up with DNA nucleotides.

• Completed mRNA can move into the cytoplasm.

Translating the RNA Code

• Proteins are made of amino acids. The order of the nitrogen bases in mRNA determines the order of the amino acids in a protein

• Three nitrogen bases on mRNA form the code for one amino acid. Each series of three nitrogen bases on mRNA is called a codon

Translating the RNA Code

• There are 64 codons, but only 20 amino acids

• Start codon: the codons which codes for an amino acid that is the beginning of a protein

• Stop codon:  codes for the end of a protein and signal that translation should stop