Protein synthesis is the process which produces proteins from the information in the DNA code.
What is protein synthesis?
The process which produces proteins from the information in the DNA code
What are the two stages of protein synthesis?
Transcription and Translation
Transcription is when the DNA code is copied (transcribed) into a single strand of RNA called messenger RNA
Translation is when the mRNA is read by a ribosome and the code is translated into a polypeptide chain.
What is transcription?
The process by which genetic information is encoded in the DNA is copied into a complementary RNA molecule
Where does protein synthesis occur?
In the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells
Where does protein synthesis occur in eukaryotic cells?
In the nucleus
Where does protein synthesis occur in prokaryotic cells?
In the cytoplasm
Why is transcription necessary?
The DNA molecule itself is too large to fit through the nuclear pores, so the smaller mRNA is used to ‘copy’ a section of DNA which codes for a protein.
If a gene codes for a certain protein, it needs to be able to make all of the amino acids which make up that protein, therefore, each section of the gene (called a codon) codes for a different amino acid.
The genome is a complete set of genes in an individuals DNA
What is the genome?
The complete set of genes in an individuals DNA
The genes in the genome encode for the different proteins a cell needs
The proteome is the full range of proteins an individual can produce
What is the proteome?
The full range of proteins that an individual can produce
Every three bases on a gene are known as a codon
What is the name for every three bases on a gene?
A codon
Each codon encodes for a specific amino acid.
What does each codon encode for?
A specific amino acid
A single gene is essentially a sequence of codons
Codons are non-overlapping, meaning that each codon codes for only its particular amino acid, and does not specify the positions of the other amino acids on the final protein
Codons are degenerate, meaning that some of the amino acids in our body can be specified by more than one codon
There are a total of 64 codons in most organisms, this is referred to as the genetic code.
How many codons are there in most organisms?
64
Three of the 64 codons in organisms are STOP codons, which signals the end of a polypeptide chain.
How many codons are STOP codons?
Three
What are STOP codons?
Codons that signal the end of a polypeptide chain
One of the 64 codons is called a START codon, and has the sequence ATG, this signals the start of the polypeptide chain.
What is the sequence for the START codon?
ATG
What is a START codon?
A codon that signals the start of the polypeptide chain
The remaining 60 codons (not STOP or START) encode for the 20 amino acids that our cells are able to use to make proteins.
The genetic code is universal, being the same in all living organisms, providing indirect evidence for evolution
The genetic code provides indirect evidence for?
Evolution
RNA is a single stranded nucleic acid molecule that is made from the same bases as DNA, except for the bases Uracil, which replaces Thymine.
What are the two types of RNA?
Messenger and transfer
Messenger RNA is transcribed from the DNA in the nucleus to produce a single stranded RNA, which is complementary to the DNA base sequence it has been transcribed from.
Messenger RNA travels from the nucleus to the ribosomes in the cytoplasm, which are proteins that translate mRNA into amino acids and synthesise the polypeptide.
Transfer RNA forms a clover-like shape and is vital for translation, it reads the mRNA codons and brings the corresponding amino acids into the ribosomes.
Each tRNA molecule has an anticodon, which is complementary to a specific codon on the mRNA. The amino acid that corresponds to a specific anticodon binds to a specific attachment site on the tRNA molecule.