Protein Synthesis:DNA Transcription & Translation

By Jessi Jones

Table of Contents

Slide Title Slide #

• What is Protein Synthesis 3• The Site of Construction 4• The Workers 5• Transcription 6• How this works 7

• DNA vs mRNA 8• tRNA 9• Codons and Their Amino Acids 10

• Ribosomes 11• Translation 12• Completion 13• References 14

What is Protein Synthesis?

• Protein Synthesis actually means the ‘construction’ of proteins.

• We need proteins for our body to grow and to work.

• Your body makes the proteins it needs everyday with the amino acids from the foods that you eat.

The Site of Construction

Every cell in your body make proteins.

There are 2 parts to protein synthesis;

Each cell has millions of construction sites

1. Transcription: copying the plans

2. Translation: reading and

constructing

The Workers

The Nucleus

the head office where all the original blue prints and important instructions are held safe as DNA.

The Ribosomesthe actual sites of construction, they are found throughout

the cytoplasm in the cell.

mRNA (messengerRNA) go into the nucleus and copy parts of the DNA and take the instructions to a ribosome.

tRNA (translatorRNA) translate the instructions on the mRNA. They carry amino acids (the building blocks), and 3 codons.

Transcription

DNA are the ‘blue prints’ for our body’s.

That’s where mRNA comes in!

DNA never leaves the nucleus!

So, the pieces of information needed for each project has to be copied and taken to the construction sites.

Messenger RNA go into the nucleus and copy the parts it needs then go out and find a ribosome.

How This Works

1. The DNA unwinds itself in one spot

1

2

a

2. mRNA attaches itself for a second and makes a copy of that part of the instructions.

a. mRNA will replace the T codon

for Ub. It will also copy a start and end code.

3. When complete, the mRNA leaves the nucleus to find a ribosome.

4. The DNA strand then winds itself back up.

DNA vs mRNA

This is a DNA double Helix.

It’s called that because it is two rows twisted together.

mRNA is just one row.

tRNA

Amino acid

tRNA

3 letter codon

This is a tRNA

ready for

attachment

It has an Amino Acid

And the 3 letter codon

Codons and Their Amino Acids

The 3 letter codons on tRNAs are specific to the amino acid they carry.

Below is a table of the 3 letter codons and the amino acids associated with them.

Ribosomes

During Protein Synthesis mRNA is used by many ribosomes at once.

tRNA

mRNA

Ribosome

Ribosomes are made up of 2 parts.

When joined there is a small space between them where the mRNA attaches and slides through.

This is also the area where the tRNAs attach and for the polypeptide chain.

Space for mRNA

Translation

1. tRNAs 3 letter codon matches the available space on the mRNA and attaches itself.

-The polypeptide is then released to coil upon itself creating a protein. - tRNA and mRNA are also released - Ribosomes break apart

2. Amino acid attaches to previous amino acid; releasing the previous tRNA continuing the polypeptide chain.

3. Repeats until end code on mRNA is reached.

Completion

The polypeptide created coils upon itself, creating a protein.

tRNAs seek specific amino acids that match its 3 letter codon.

mRNAs return to the nucleus to repeat the transcription process.

Ribosome’s float around the cytoplasm waiting for the next job.

Protein synthesis begins again!

Proteins

References

• J. Creager, J. Black, & V. Davison. 1990. Microbiology: Principles and Practice. Prentice-Hall, Inc. 839 pp.

• P. Raven & G. Johnson. 1999. Biology. WCB?McGraw Hill Publishing. 1284pp.

• W. Purves, D. Sadava, G. Orians, H. Heller. 2001. Life: The Science of Biology. WH Freeman & COmpany. 1044 pp.

• S. Mader. 1987. Biology: Evolution, Diversity amd the Environment. William C. Brown Publishers. 772pp.