6.1.1 Cellular Control Flashcards
Define mutation
Mutation are changes in base sequence of DNA. Can be caused by chemical or agents known as mutagens
What type of mutations are there
Point mutation- involves base substituion
Missense - changes an amino acid in the primary structure
Nonsense - introduces an early stop codon, truncating the protein
What does deletion and insertion do
Cause a frameshift, code is shifted along and reads as different triplet codons,major chnages in protein structure
Define transcriptional factor
Eukaryotes:Control transcription by binding to promoter regions of genes and encouraging or inhibiting the binding of RNA polymerase
Prokaryotes: the lac operon controls transcription of metabolic genes
Give an example of a prokayotic transcriptional control
Regulatory gene- Lac I codes for repressor protein that normally blocks RNA polymerase from binding to the operator
When lactose is present, inhibits the repressor protein allowing RNA polymerase to transcribe lac Z and Y for lactose metabolism
Describe how transcription factors control gene expression in eukaryotic cells
Can bind to promoters in the DNA, adding or inhibiting transcription,turnes gene on or off
Explain why the control of gene expression in eukaryotes and prokaryotes is vital to cell function
All cells contain entire genome, potential to transcribe or translate every single gene , many proteins are not needed all the time, transcribing and translating them would be a waste of resources
Cells would not be able to differentiate and specilaise as specfic cells e,g RBC requiers lage quanity of proteins
Explain the difference between introns and exons found in DNA
Exons are regions that code 4 polypetides
Introns do not code 4 polypeptides and removed before translation, can be involved in gene regulation
One gene can code for several different polypeptides, explain how this is possible (post transcriptional modifcation)
One gene can have several exons. Exons of the mRNA can be shuffled into different orders and joined up. Order of AA will change and alter the the primary and tertiary structure of the PP
Describe how post translational protein modification occurs
After translation, proteins will have carbohydrates and lipids added to them. Forms glycoproteins and lipoprpteins, occurs in golgi apparatus. Proteins can also be activated or phosphorylated, alter shape. One moleucle that activates them is cyclic protein kinase
Explain why post translational modifation is needed
Proteins need to have a specfic shape to function
Adding phosphate, lipids or carbohydrates will alter the tertiary or quaternary structure
Define homebox and hox genes
Homebox genes - ancient,highly conserved genes that code for homeodomain sequences in proteins that regulate anatomical development
Hox genes - subset of homeobox genes, regulating the axes of embryos, dictating the position of anatomical features
State the meaning of the term ‘highly consevered’ in association to hox genes
Genes have not mutated very much over a long period of time
Vitally important 4 survival because any any mutated version have clearly not been selected for and survived
Describe the sequence of events that occur during apoptosis
Enzymes will break down the cell cytoskeleton
Cytoplasm will became dense with tightly packed organells
Chromatin condenses and the DNA and nuclear envelope break down into fragments.
Blebs start to form, conversion of the cell into many small vesicles which will be phagocytosed
Explain the importance of apoptosis
Important in development, without it ineffective immune cells would not be removed and digits would not form
Tumour can occur if rate of apoptosis occurs
Summarise the 4 levels in which genes are regulated
Transcriptional- genes can be turned on or off
Post transcriptional -mRNA can be modified which regulates translation and types of protein produced
Translational- translation can be stopped or started
Post translational- proteins can be modified after synthesis which chnages their function
Define both promoter and operator in regards to gene expression
Promoter - region of DNA required to allow transcription of the gene to take place
Operator - segment of DNA to which a repressor binds to inhibit transcription of a gene
Define both regulatory and structural gene do
Regulatory - controls which genes are expressed at different points in time
Structural - gene that codes for proteins that has a function with a cell
