PROTEIN SYNTHESISIn this experiment we modeled the structure of DNA and the processes

involved in protein synthesis

By: Shelley Quirk

42 toothpicks 18 milk bottles cut in half (36 halves) –

sugar 18 raspberry lollies cut in half-

phosphate 25 jelly beans cut in half (5 of each 5

colours)- bases: Adenosine- orange Thymine- purple Cytosine- pink Guanine- green Uracil- blue 4 jelly snake, aprox. 6cm long, different

colours A4 white paper representing a cell Colored paper circle, 6cm diameter- a

ribosome Clean sharp knife Cutting board Gloves Scissors Marking pen Heinemann Biology textbook

Equipment

DNA is a double stranded helix molecule made of subunits called nucleotides.

Each nucleotide contains a sugar (deoxyribose), a phosphate, and a base.

There are four bases (adenosine, thymine, cytosine and guanine).

Alternate sugar and phosphates form the sides with bases connected to the sugars making “rungs” like a ladder.

The information about the number, type and sequence of amino acids, needed to make a protein molecule, is found as a code in DNA.The code- a sequence of bases.One gene sequence codes for one polypeptide (a single chain of many amino acids)A set of 3 bases (a codon) codes for one amino acid of a polypeptide. A protein is one or more polypeptides.

a gene length of DNA unwinds in the nucleus

RNA polymerase enzyme moves along the exposed single DNA strand linking complementary RNA nucleotides together to form a messenger RNA strand. RNA contains the base uracil where thymine is found in DNA.

The mRNA strand is then modified so that it only consists of the base sequence that will code for the protein. It removes the non-coding regions, introns, while still in the nucleus by splicing the coding regions, exons, together.

The modified mRNA then moves from the nucleus into the cytoplasm

The start codon (AUG) and a stop codon control the length of the mRNA strand.

In the cytoplasm, an enzyme attaches amino acids to tRNA molecules. Each type of amino acid is attached to its specific tRNA.

The modified mRNA moves out of the nucleus into the cytoplasm.

TRANSLATION The start codon (AUG) end of the mRNA strand binds onto a ribosome. A tRNA

carrying the amino acid methionine at one end and anticodon (UAC) at the other, binds to the mRNA start codon within the ribosome.

DNA strand

Amino acid forming polypeptide bond (jelly snakes)

Ribosome

mRNA strand

A second tRNA binds to the next codon. Its amino acid links to the polypeptide bond of the first amino acid.

The first tRNA is released from the ribosome. The ribosome moves along the mRNA strand one codon at a time. Two tRNAs at a time are temporarily bound within the ribosome and their amino acids linked together

DNA strand

Amino acid forming polypeptide bond (jelly snakes)

Ribosome

mRNA strand

A polypeptide chain forms (jelly snakes)

When a ‘stop’ codon is reached the polypeptide chain is released into the

cytoplasm