Module 6.1.1 - Genetics of living systems Flashcards
What are the 4 types of DNA mutations that can happen?
- substitution
- insertion
- deletion
- frame shift
What is substitution?
- changes nucleotide/base for another
- could code for another amino acid
- structure/bonds could change
- could change function
What are the 3 types of substitution and what do they do?
Nonsense - mutation results in 1 of the 3 stop codons, protein is shorter, wont fully be effective, stop working
Missense - different amino acid sequence being coded for
Silent - change to base makes no difference, no effect had on amino acid and protein
What is insertion?
- extra nucleotide added in
- changes all codons after it
- could change all amino acid
What is deletion?
- nucleotide is removed
- could change all amino acids
- changes all codons after it
What is frame shift?
- caused by deletion and insertion
- cause all further amino acids to be changed
- some change shape/shorter
What is an example of a substitution mutation?
Sickle cell anaemia
- swapping A for T in a gene for haemoglobin
- structure of red blood cells change
What are the effects of mutations?
Neutral - normal functioning proteins still synthesised, phenotype of organism is unchanged
Harmful - proteins not synthesised or are non functional, phenotype of organism is negatively impacted
Beneficial - protein synthesised with a new and useful characteristic and phenotype
What are some causes of mutations?
- radiation
- x rays
- chemicals in cigarettes smoke
- chemicals in caffeine
- UV light
What is an operon?
Section of DNA that contains cluster of genes that’re all transcribed together as well as control elements and a regulatory gene
- more common in prokaryotes than eukaryotes
What is a Lac Operon?
Only produce enzymes needed to respire lactose when present, if not, repressor is present to stop lactose being produced
What are the parts of the Lac Operon when its turned off?
- regulatory gene
- promotor
- operator
- structural genes
- RNA polymerase
- active repressor
- mRNA
- DNA
What are the parts of the Lac Operon when its turned on?
- regulatory gene
- promotor
- operator
- RNA polymerase
- lactose utilisation
- mRNA
- protein
- lactose
- inactive repressor
- enzyme for lactose utilisation
What do structural genes do?
Code for proteins
What does the regulatory gene do?
Codes for transcription factor
What do the control elements (promotor, operator) do?
Promotor - RNA polymerase binds to it
Operator - transcription factor binds to
How does the Lac Operon control protein production?
Changes shape of repressor so doesn’t bind to the operator
What are transcription factors?
- proteins that will bind to DNA and move in from cytoplasm
- attach RNA polymerase to DNA
- most are in an inactive form and activated by hormones
- some only in certain cell types
- some only present at particular stages of development
What does posttranscriptional level mean?
Editing of mRNA
What is an intron?
Section of gene that doesn’t code for an amino acid
What is an exon?
Does the code for amino acids
What is splicing?
Introns are removed when gene is transcribed, functional exons are joined together, causes introns to form a loop shape
What happens during splicing?
- intron removed and form a loop shape due to spliceosomes
- only exons are left and spliced together
- mRNA may leave nucleus into cytoplasm for next stage of protein synthesis
What are snRNP’s?
Small nuclear ribonucleoproteins
What are homeobox sequences?
- highly conserved regions of DNA
- all organisms have them, apart from bacteria
- 180 base pairs
What are hox genes?
- class of homeobox genes in animals to position body parts
- hox genes have homeobox genes that code for homeodomains
- every hox gene is a homeobox gene, but not every homeobox gene is a hox gene
What are homeodomain proteins?
- hox genes have homeobox genes that code for homeodomains
-transcription factors to activate/repress genes that regulate mitosis, apoptosis and cell cycle
What is apoptosis?
- programmed cell death in development
- series of biochemical events leader to an orderly and tidy death
Why should the rate of cells dying balance the rate of cells produced by mitosis?
- not enough apoptosis leads to tumors forming
- too much apoptosis leads to cell loss and degeneration
How is apoptosis controlled?
- hox genes regulate mitosis and apoptosis
- expression of these genes is regulated by stimuli and different stresses
What are some internal controls of apoptosis?
- damage to DNA detected in cell cycle
- genes are expressed that cause cell to pause/triggers apoptosis
- release of hormones
- physiological stress
What are some external controls of apoptosis?
- change in light intensity, temp
- pathogen attack
- lack of nutrients
- drugs can also have effect
What is the process of apoptosis?
- normal cell
- cell begins to bleb at the start of apoptosis, nucleus and cytoskeleton starts to disintegrate
- cell fragments produced with intact plasma membranes and containing organelles
- cell fragments are ingested and digested by phagocytic cells
What are the stages of interphase?
- G1
- G1 checkpoint
- S
- G0
- G2
- G2 checkpoint
- M checkpoint
What are the stages of the cell cycle?
- interphase
- nuclear division
- cytoplasmic division
What happens in G1?
- cell increases in size
- proteins are synthesised
- organelles divide and replicate
- DNA damage is checked for damage at the checkpoint
What happens in G2?
- increases in size
- energy stores grow
- checkpoint checks for errors
What happens in S stage?
- synthesis of DNA
What happens in G0?
- errors are picked up
- leave cell and undergo differentiation
What happens in M checkpoint?
- makes sure chromosomes are attached to spindle fibres
- in metaphase
