HELLO
PROTEIN SYNTHESIS ESSAY
The Perfect Essay for Q4.2, June - 2012
Proteins are essential for the functioning g of all living cells and therefore must be correctly manufactured inside the cell. Mistakes (mutations) may occur, however, during the process of protein synthesis
Write an essay in which you describe the process that results in the formation of fully functional proteins and explain how gene mutations affect this process
There are FOUR compulsory points to this essay (see asterisk *)
Transcription* :
A particular gene•on a DNA strand codes for a specific protein which serves as a template for mRNA
The DNA strand unzips and a message is transcribed from DNA onto mRNA
Each group of three nitrogenous bases on mRNA, known as a codon codes for a particular amino acid
mRNA leaves the nucleus via the nuclear pore and carries the code to the ribosome* (the site of protein synthesis ) in the cytoplasm ( +4 = Max 5)
Translation * :
mRNA strand formed in the nucleus attaches to the ribosome
mRNA provides the code for the joining of the amino acids to form a specific protein
An anticodon on the tRNA (loop) determines which amino acid is picked up
Specific tRNA brings a particular amino acid to the template formed by mRNA
Amino acids join in sequence• to form a polypeptide chain
Peptide bonds form between the amino acids
tRNA moves off from ribosome and is ready to pick up another amino acid of the same type
The whole process is controlled by enzymes* ( + 6 = Max+ 7]
Impact of gene mutations on the synthesis of proteins
A gene mutation occurs as a result of a change in the nucleotide sequence in the DNA molecule
Gene mutations can occur during :
1. DNA replication•/
2. cross over during meiosis
3. transcription of DNA to mRNA
4.
POINT MUTATION* only causes an alteration at a specific place in the DNA strand, resulting in an alteration of one amino acid
Hence changing the type of protein formed
Gene mutation where one or more nucleotides are lost or inserted may result in a FRAMESHIFT MUTATION *
After such deletion or insertion all the base triplets are altered and consequently also the amino acids
Instructions for protein synthesis change and result in the formation of a faulty protein or even no protein at all
Various genetic disorders, e.g. albinism and sickle-cell anaemia can be caused by genetic mutations*
(2+3= Max 5)
Synthesis: You will be awarded 3 extra marks if the essay is well structure (as above) – which demonstrates insight and understanding of the question (in other words, no waffle, just fact, fact, fact)
