Cellular Control Flashcards
What are transcription factors?
Proteins that move from the cytoplasm to the nucleus
In e.coli…
The protein lactase is only made when lactose is actually present
Genes are switched on to make this protein
What are epigenetics?
Heritable changes in in gene function without a change to the base sequence of DNA
What does acetylation do to the process of transcription?
Decreased acteylation of histone decreases transcription
What is a lac operon?
A group of three genes
LacZ, lacY and lacA
What is an operon?
A group of genes that are under the controlof the same regulatory centre mechanism and are expressed at the same time
What does the respressor protein in lac operon do?
Prevents the transcription of the structural genes in the absence of lactose
What are the different ways in which genes are operated?
Transcriptional
Post-transcriptional
Translational
Post-translational
What is a mutation?
Change in the sequence of bases in DNA
How is a change in the sequence of DNA caused?
Substitution, deletion or insertion of one or more nucleotides within a gene
What is a point mutation?
A mutation in which only one neculeoride is affected
What is a mutagen?
A mutagen is a chemical, physical or biological agent which causes mutations
What are antioxidants also known as?
Anticarcinogens because of their ability to negate the effects of mutagens (such as free radicals)
What are free radicals?
Oxidising agents
Where is radial symmetry seen?
Diploblastic animals like jellyfish
They only have a top and a bottom (no left or right sides)
What kind of symmetry is seen in most animals?
Bilateral symmetry
Where is asymmetry seen?
Sponges
What are somites?
Segments in the embryo
What is an example of a beneficial mutation?
The ability to digest lactose
How does chromatin remodelling affect the transcription of genes?
Acetylation / phosphorylation of histones makes them more nagtuve and causes them to coil less tightly (euchromatin)
This is the opposite of heterochromatin
What is heterochromatin?
Tightly wound DNA causing chromosomes to be visible during cell division
What is another way in which histones can be modified?
Methylation make histones more hydrophobic so they bind more rightly to each other and the DNA coils more tightly
Prevents transcription of genes
What is lac operon?
Structural genes that code for three enzymes
B-galactosidase, lactose permease, transacetylase
What is the role of cyclic AMP in transcriptional control?
Increase the rate of transcription to produce the required quantity of enzymes to metabolise lactose efficiently
What does a cap (a modified nuc,emotive) help do?
Help stabilise mRNA and delay degradation in th cytoplasm
Aids binding of mRNA to ribosomes
What is an example of translational control?
Protein kinases, enzymes that catalyse the addition of phosphate groups to proteins
Addition of a phosphate group changes the tertiary structure = changes the function of a protein
Protein kinases are important regulators of cell activity (+ are activated by secondary messenger, cAMP)
What are examples of post-translational control?
- Addition of non-protein groups
- Modifying amino acids and formation of bonds e.g. disulfide bridges
- Folding / shortening of proteins
- Modification by cAMP
What is a homeodomain
60 amino acids in a protein that is highly conserved in animals, fungi and plants
