F215 Genetic Control

Frage	Antworten
Genetic Terminology	Genetic Terminology
Co-dominance	Alleles which both contribute to the phenotype They are both expressed in the phenotype
Dominant allele	an allele which is always expressed in the phenotype, even if a different allele for the same gene on the other chromosome is present
Recessive allele	an allele which is only expressed if both alleles are identical and there are no dominant alleles
Gene	length of DNA, sequence of nucleotide bases which codes for one or more polypeptide occupies a specific locus on the DNA
Genome	all of the DNA an organism has
Polypeptide	chain of amino acids joined by peptide bonds forming a polymer
Chromosome	One molecule of DNA which contains many genes they come in homologous pairs, one from the mother and one from the father
Histone Protein	DNA double helix associates with histone protein to produce chromosome
Transcription	the production of a single stranded mRNA copy of a gene
Translation	the assembly of polypeptides using mRNA and ribosomes
Codons	triplets of nucleotide bases
control of protein synthesis and protein activation	control of protein synthesis and protein activation
Switched off	Genes which aren't being transcribed. The proteins they code for aren't being produced.
Interphase	Before mitosis and meiosis, the cells DNA unravels and replicates = 2 copies of each chromosome in each cell
Switched on	Genes which are being transcribed are described as being switched on. These genes are being used to produce polypeptides
Operons	protein production in prokaryotes and eukaryotes involves: - structural genes - control elements - often regulatory genes
Structural Genes	genes which codes for useful enzymes
control element	made up of: - promotor = RNA polymerase binds to - operator = transcription factor binds to
regulatory gene	codes for transcription factor
transcription factor	protein that binds to the operator part before the gene, that switches the gene on or off there are two types: - activator - repressor
activator factor	in the presence of the activator factor, the gene will be transcribed and the proteins will be synthesised
repressor factor	in the present of the repressor factor, the gene will not be transcribed and the proteins will not be synthesised
environmental changes	changes in the environment can cause the binds or structural change to the protein of the transcription factor on the gene this will mean that the transcription factor will not longer be able to bind to the operator part, and the opposite will take place - genes which were switched off, will be transcribed - genes which were switched on, will stop being transcribed
Lac operon	E.coli normally respires glucose, but when glucose levels are low, lactose can be used the gene Lacl codes for enzymes which breakdown lactose e.g. beta-galactosidase and lactose permease normally (in conditions where there high concentration of glucose) a repressor factor is produced by the regulatory gene which binds to the operator part on the gene to stop the synthesis of these enzymes when there is a higher concentration of lactose than glucose, the lactose molecules bind to the transcription factor, changing the shape of the repressor factor so it can no longer bind to the operator site and therefore the transcription of the end

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