The Perfect Essay for Q4.2, June - 2012 Proteins are essential for the functioning 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)
Posted on: Sat, 08 Jun 2013 09:48:25 +0000
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