Control Of Gene Expression Flashcards
What is all the different types of mutations that can happen
Addition
Deletion
Substitution
Inversion
Duplication
Translocation
What does universal mean
The same 3 bases on mRNA codon/ DNA triplet codes for the same amino acids in all organisms
Non overlapping
Each base is read once in a triplet
Degenerate
More than one triplet or codon codes for an amino acid
What is a gene mutation
A change to a single base in the DNA base sequence of a gene
Mutations occur…….
……randomly and spontaneously
What is a silent mutation
The mutation does not change the amino acid coded for so will have no effect on the polypeptide chain
What is a chromosomal mutation
When the daughter cells during meiosis produce too many chromosomes
What is inversion mutations
When a segment of bases or a chromosome is reversed end to end
What is a duplication mutation
A doubling part of a chromosome, of an entire chromosome or even the whole genome
What is translocation mutations
When groups of base pairs relocate from one area of the genome to another usually between non homologous chromosomes
What are mutagenic agents
They increase the rate of spontaneous mutation
Examples of mutagenic agents
X rays
Alpha beta particles radiation
Ultra violet radiation
Proteome
The full range of protein a cell is able to produce
Genome
Full genetic base sequence of all the DNA in the cell
What are the different types of stem cells
Totipotent
Pluripotent
Multipotent
Unipotent
Totipotent stem cells
Differentiate into any types of cells
Pluripotent
Differentiate into most types of cells
Multipotent
Differentiate into limited number of cells
Unipotent
Single type of cells e.g cardiomyocytes
Applications of stem cells to medical research
Producing tissues for skin grafts
Research into producing organs for transplant
Research into how cells become specialised
Research into cancer and other serious diseases
The use of stem cells to cure such diseases as Parkinson’s disease
If stem cells divide out of control what might happen…
…leads to formation of a tumour
What is the promoter region
One or more base sequences found upstream a gene to control the expression of that gene
Transcription factors
Proteins which when activated bind to the promoter region of a gene stimulating RNA polymerase to being transcription of the target gene
What is the point of RNA interference
Prevents and limits protein synthesis and to stop the waste of ATP making proteins that are not necessary
Why does some protein still be made after RNA interference
RNAi is used to reduce or silence a translation of a protein. Specific proteins are still produced because not all mRNA has been destroyed
How does RNAi work
RISC inhibits gene expression by binding to the complementary mRNA by either:
1) the mRNA is hydrolysed by an enzyme (cut into fragments)
2) inhibits the initiation of ribosomal translation; ribosome is prevented from attaching to the mRNA.
What is epigenetics
Involves inheritable changes in gene expression without changes to the DNA base sequences
What can inhibit transcription/ silence a gene
Decreased acetylation of histones
Increased methylation of DNA
What can activate a gene
Increased acetylation of histones
Decreased methylation of DNA
Differences between malignant and benign tumours
Malignant - tumours are fast growing, non-capsulated and they metastasise
Benign - tumours are slow growing, surrounded by a capsule and do not metastasise
The rate of cell division is controlled by two types of genes:
Proto-oncogenes which stimulate cell division
Tumour suppressor genes which slow cell division
Mutations in proto oncogenes and tumour suppressor genes can increase…
The risk of developing cancer
What happens when proto oncogenes are mutated
Results in over stimulation of cell division. That cell is permanently switched on.
What happens when tumour suppressor genes are mutated
Gene becomes inactivated so it stops inhibiting cell division, o the rate of cell division increases
Explain what is meant by the terms totipotent and pluripotent.
• totipotent cells can give rise to a complete human/all cell types;
• pluripotent can only give some cell types;
Explain how cells produced from stem cells can have the same genes yet be of different types.
• {not all / different} genes are switched {on / off} /active / activated ;
• correct and appropriate reference to factors /mechanisms for gene switching ;
• e.g. reference to promoters / transcription factors
Describe the mechanism by which a signal protein causes the synthesis of mRNA.
• signal protein {binds to / joins to / interacts with / activates}
• receptor on surface membrane;
• messenger molecule moves from cytoplasm and enters nucleus;
• {produces / activates} transcription factor;
• binds to promoter region;
• RNA polymerase transcribes target gene;
Explain how oestrogen enables RNA polymerase to transcribe its target gene.
• Oestrogen diffuses through the cell membrane;
• attaches to ERα receptor;
• ERα receptor changes shape;
• ERα receptor leaves protein complex which inhibited it’s action;
• oestrogen receptor binds to promoter region;
• enables RNA polymerase to transcribe target gene.
Compare the structure of dsRNA and DNA.
• Similarities; 2 max
• Polynucleotides/polymer of nucleotides;
• Contain Adenine, Guanine, Cytosine;
• Have pentose sugar/5 carbon sugar;
• Double stranded/hydrogen bonds/base pairs.
• Differences; 2 max
• dsRNA contains uracil, DNA contains thymine;
• dsRNA contains ribose DNA contains Deoxyribose;
• dsRNA is Shorter than DNA; fewer base pairs in length;
Explain how the methylation of tumour suppressor genes can lead to cancer.
• Methylation prevents transcription of gene;
• Protein not produced that prevents cell division / causes cell death / apoptosis;
• No control of mitosis.
Describe how alterations to tumour suppressor genes can lead to the development of tumours.
• (Increased) methylation (of tumour suppressor genes);
• Mutation (in tumour suppressor genes);
• Tumour suppressor genes are not transcribed/expressed
• OR
• Amino acid sequence/primary/ tertiary structure altered;
• (Results in) rapid/uncontrollable cell division;
Describe what is meant by a malignant tumour.
• mass of undifferentiated / unspecialised / totipotent cells;
• uncontrolled cell division;
• (not ‘repeated’)
• metastasis / (cells break off and) form new tumours /
• spread to other parts of body;
Describe how altered DNA may lead to cancer.
• (DNA altered by) mutation;
• (mutation) changes base sequence;
• of gene controlling cell growth / oncogene / that monitors cell division;
• of tumour suppressor gene;
• change protein structure / non-functional protein / protein not formed;
• (tumour suppressor genes) produce proteins that inhibit cell division;
• mitosis;
• uncontrolled / rapid / abnormal (cell division);
• malignant tumour;
Describe how alterations to tumour suppressor genes can lead to the development of tumours.
• (Increased) methylation (of tumour suppressor genes);
• Mutation (in tumour suppressor genes);
• Tumour suppressor genes are not transcribed / expressed OR Amino acid sequence / primary structure altered;
• (Results in) rapid/uncontrollable cell division;
Define epigenetics
• Heritable phenotype changes (gene function) that do not involve alterations in the DNA sequence/mutation.
