1. Module 1 Cellular Control

2. ...state that genes code for polypeptides, including enzymes... A gene is a length of DNA that codes for one or more polypeptides. Each gene occupies a specific place or LOCUS on the chromosome. The DNA in the chromosomes is associated with histone proteins. Genes code for polypeptides such as: 1.Enzymes 2.Antigens 3.Actin and myosin in muscle cells 4.Haemoglobin

3. ...Describe the way in which a nucleotide sequence codes for the amino acid sequence in a polypeptide... DNA codes for the sequence of amino acids in a polypeptide, but remember there are NO amino acids in the DNA molecule. Transcription is the FIRST stage of protein synthesis. 1.A gene unwinds and unzips 2.Hydrogen bonds between complementary bases break 3.Activated RNA nucleotides bind, with hydrogen bonds to their exposed complementary bases (U with A, G with C, and A with T on the template strand). This is catalysed by RNA Polymerase. 4.Two extra phosphoryl groups are released. 5.The mRNA produced is a copy of the base sequence on the coding strand of the length of DNA. 6.The mRNA is released from the DNA, out of the nucleus, through a nuclear pore, to a ribosome.

4. ...Describe with the aid of diagrams, how the sequence of nucleotides within a gene is used to construct a polypeptide, including the roles of mRNA, tRNA and ribosomes... TRANSLATION is the second stage of protein synthesis, where the amino acids are assembled into a polypeptide. The steps are as follows: 1.A molecule of mRNA binds to a ribosome. Two codons are attached to the small subunit of the ribosome and exposed to the large subunit. The first mRNA codon is always AUG(Methionine). 2.A second tRNA, bearing a different amino acid, binds to the second exposed codon with its complementary anticodon. 3.A peptide bond forma between the two adjacent amino acids. 4.The ribosome now moves along the mRNA, reading the next codon. A third tRNA bring another amino acid, and a peptide bond forms between it and the dipeptide. The first tRNA leaves. 5.The polypeptide chain grows until a stop codon is reached.

5. ...State the cyclic AMP activates proteins by altering their three dimensional structure.. Some proteins have to be activated by a chemical cyclic AMP, that, like ATP is a nucleotide derivative. It activates proteins by changing their 3D shape, so that their shape is a better fit to their complementary molecules..

6. ...state that mutations cause changes to the sequence of nucleotides in DNA molecules... A MUTATION is a change in the amount of, or arrangement of, the genetic material in a cell. Mutations associated with mitosis are somatic and are not passed on the offspring. They may however, contribute to the ageing process or may lead to cancer. Mutations associated with meiosis and gamete formation can be inherited. There are 2 main classes of DNA mutations: 1.POINT MUTATIONS – in which one base pair replaces another. These are also called SUBSTITUTIONS. 2.INSERTION/DELETIONS MUTATIONS – in which one or more nucleotide base pairs are inserted or deleted from a length of DNA. These cause a FRAMESHIFT. WATCH THIS NOW: http://www.mefeedia.com/watch/21777427http://www.mefeedia.com/watch/21777427 Many genetic diseases are the result of DNA mutations. E.g. -In 70% of cases of Cystic Fibrosis, the mutation is the deletion of a triplet of base pairs. -Sickle cell anaemia results from a point mutation -Huntington’s disease results from an expanded triplet nucleotide repeat – a stutter...

7. ..explain how the mutations can have beneficial, neutral or harmful effects on the way a protein function.. Mutations with neutral effects: If a gene is altered by a change to its base sequence, it becomes another version of the same gene. It is an allele of the gene and may cause no harm if: 1.The mutation is in a non-coding region of the DNA. 2.It is a silent mutation. Mutations with harmful or beneficial effects: Early humans in Africa almost certainly had dark skin. The pigment melanin protected them from the harmful effects of UV light and they could still synthesise vitamin D. If a human in Africa had a mutation to some of the genes determining skin colour, producing paler skin, they would have burned and suffered from cancer. BUT as humans migrated to more temperate climates, the sunlight was not intense enough to cause vitamin D to be made by those with dark skin, so humans with paler skin obviously had an advantage as they could synthesis more vitamin D.

8. ......Explain genetic control of protein production in a prokaryote using the lac Operon....... Watch these in THIS order.. 1 - http://www.mefeedia.com/watch/21777614http://www.mefeedia.com/watch/21777614 2 - http://www.mefeedia.com/watch/21777611http://www.mefeedia.com/watch/21777611 3 - http://www.mefeedia.com/watch/21777608http://www.mefeedia.com/watch/21777608 So, to describe the Lac Operon in steps.... Next slide...

9. ......Continued..... WHEN LACTOSE IS ABSENT: 1.The regulatory gene makes RNA via transcription and translation. The RNA then makes a protein, called the repressor protein. 2.The repressor protein binds to the operator region. In doing so, it covers part of the promoter region, where RNA polymerase normally attaches. 3.RNA polymerase cannot bind to the promoter region, so the structural genes Z and Y cannot be transcribed into mRNA. 4.Without mRNA the Z and Y genes cannot be translated and the enzymes B- galactosidase and permease cannot be synthesised. WHEN LACTOSE IS PRESENT: 1.Once again, the regulatory gene makes RNA via transcription and translation, and because lactose is present, RNA makes a lactose inducer molecule which binds to the repressor molecules and changes its shape. The repressor protein dissociates from the operator region. 2.The promoter region is now unblocked ad now RNA polymerase can initiate the transcription of mRNA for the structural genes Z and Y. 3.As mRNA is present the structural genes can be translated into the enzymes B- galactosidase and permease.