CELLULAR CONTROL Flashcards
what is a mutation?
random change of the genetic material
can be essential for evolution
they might be harmful, adaptive or neutral
change in the sequence base of DNA or RNA
can occur spontaneously during DNA replication and transcription
what is meant with the term “mutagenic”?
list some mutagenic factor.
have the ability to cause mutation.
tobacco smoke, UV light, XRAY , gamma rays
types of mutation and describe them
SOMATIC MUTATION = occurs in cell body , may have little effect of organism, not passed on to offspring, associated with mitotic division, may cause cancerous tumour
GERMLINE/ MEIOSIS MUTATION = occurs in gametes ,significant because can be transmitted to offspring
what can a mutation cause?
can change the structure of the chromosome or just change a single nucleotide
what is the change in chromosome structure knows as, and list the types.
CHROMOSOMAL ALTERATION
-deletion
-duplication
-inversion
-insertion
-translocation
DDIIT
what can chromosomal alteration cause?
very serious as they can cause death organisms, but if survives, organism may be affected in different ways
what are the types of DNA mutation?
POINT MUTATION AND INDEL MUTATION
define and describe point mutation
-occurs when one specific nucleotide base pair is added, deleted or changed, replaced within a genome
-one base pair replaces another
-occurs when cell is dividing/replicating
-arise when DNA polymerase inserts, change, or deletes a base pair within the DNA while it is forming a new complement strand which can then change the amino acid
-when occurs in somatic cells, can arise cancer
what are the types of point mutation?
SILENT
MISSENS
NONSENSE
SILENT MUTATION:
is a codon change that has no effect on amino acid sequence, primary secondary and tertiary structure not affected
possible due to the degenerate nature of the genetic code.
MISSENSE MUTATION:
-occurs when one base pair substitution generates a codon that codes for a different amino acid
-changes sequence of amino acid
-completely changes the amino acid produced, affects protein function and prevents it from carrying it s normal function
sickle cell anaemia is a result of missense mutation
NONSENSE MUTATION:
occurs when the substitution of a single base pair creates a stop codon instead of a codon that produces an amino acid.
will result in protein that will not function, will be most likely to be degraded within cell
DUCHENNE is a result of nonsense mutation
giving rise to a truncated polypeptide
describe indel mutation
insertion or deletions cause FRAMESHIFT
one or more nucleotide pairs are inserted or deleted from the sequence. This type of mutation alters the sequence of nucleotides after the insertion/deletion point known as a frameshift.
what is meant by operon?
group of genes that are under the same regulatory mechanism and are all transcribed in 1 single unit, therefore can be transcribed all together
why is an operon useful?
because the gene that codes for protein involved in one specific metabolic pathways can all be switched on or off together
give an example of operon
lac operon
suggest why and when the lac operon might be used
e.coli uses glucose as respiratory substrate, however when glucose is unavailable and and lactose is available, this can be used as respiratory substrate.
However lactose metabolism require different proteins/enzymes, compare to those used for glucose
why are lactose proteins not produced all the time?
to conserve energy and resources
where is the gene that codes for protein used in lactose metabolism located?
in an operon - THE LAC OPERON, which is a group of genes involved in lactose metabolism
describe the structure of the lac operon
lac I (located near the lac operon, regulatory gene) , promoter, lacO (operator), lac Z, lacY and lacA
describe the function of each structure that makes up the lac operon
lac I = codes for repressors protein , which prevent transcription of structural genes
promoter= RNA polymerase binding site to begin transcription
lac O= repressor protein binding site to prevent RNA polymerase binding to promoter , thus preventing transcription
lac Z = B-galactosidase enzyme production to convers lactose into glucose and galactose
lac Y = lactose permeate (membrane carrier protein) which help transport lactose into the bacterial cell
what are lacz,lacy and lacA known as?
structural genes
describe the step involved during lac operon transcription REPRESSION.
no lactose –> lac genes transcription repressed –> genes turned off. BUT HOW?
1. lacI is always on
2. repression protein production
3. binds to operator
4. RNA polymerase prevented from binding to the promoter, therefore no transcription of the structural genes can occur
what is lactose also known as?
inducer = have the ability to turn on genes
describe the step involved during lac operon transcription INDUCTION.
presence of lactose
1. lactose bind to repressor protein
2. change of shape of repressor protein
3. prevented form binding to operator
4. RNA polymerase able to bind to operator
5. transcription can occur
when is the lac operon expressed?
ONLY WHEN GLUCOSE IS UNAVAILABLE AND LACTOSE IS AVAILABLE, to conserve energy
what are the transcription factors?
proteins that control the switching off and on of genes
can be ACTIVATORS (boost transcription) or REPRESSOR (decrease transcription)
bind to specific receptors PROMOTER (enhancer or silencer)
what can transcription protein cause after binding to promoters?
make easier for RNA polymerase to bind
make difficult for RNA polymerase to bind
what must occur for gene transcription?
RNA polymerase must attach DNA of gene
however in eukaryotic:
rna polymerase must first bind to a basal transcription factor in order to bind to a promoter
what is meant by post-transcriptional gene regulation?
regulation when DNA has been transcribed into mRNA
happens only in eukaryotes
what are INTRONS
sections of DNA that are non-coding, stays in the nucleus and are not expressed
what are EXONS
sections of DNA that are coding, leave the nucleus and are expressed
describe transcription
DNA transcribed into a primary rRNA (RNA)
RNA is edited to remove introns
exons are joined together by endonuclease enzyme
mRNA produced
leaves the nucleus
what is meant by post-translational level of gene regulation?
activation of proteins, which can be done by being PHOSPHORYLATED
how does the enzyme/ protein activation occur?
1 signalling molecule bins receptor on plasma membrane of target cell
2 activates transmembrane protein, which the activates G protein
3 G protein activates adenyl cyclase enzyme
4. adenyl cyclase catalyses the production of cAMP from ATP
5. cAMP activates protein KINASE A (PKA)
6 PKA catalyses phosphorylation of various protein, hydrolysing ATP in the process
7 phosphorylation activates many enzymes int he cytoplasm
8 PKA may phosphorylate another protein that then enters the nucleus and ACT AS A TRANSCRIPTION FACTOR TO REGULATE TRANSCRIPTION
what are the genes that controls morphogenesis?
HOMOETIC GENES
what is meant whit morphogenesis?
the process that causes an organism to form its shape
what is a subset of homeotic genes known as?
homeobox genes
what does the homeobox gene contain?
homeobox, which is a 180 DNA base pair, encoding 60 amino acids sequence
what is one characteristic of homeobox?
they are highly conserved in plant and animals throughout evolution
what does a homeobox code for?
a protein called HOMEODOMAIN
what is the role of protein that contains homeodomain?
transcription factors
what is a subset of homeobox gene called?
hox genes
describe hox genes:
type of homeobox genes found only iN ANIMALS
involved in the correct positioning of body parts in an organism
found in all blutterian animal, which means that an ancestor must have existed of all bilaterians
how are hox genes regulated?
regulated by GAP genes AND PAIR-RULE gene , which are then regulated by maternally supplied mRNA
summarise the structure of homeobox genes:
homeotic genes are composed of homeobox genes, which contains homeobox that codes for homeodomain, a subset of homeobox genes are know as hox genes
homeotic genes
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homeobox genes
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homeobox
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hox genes
what happens after a hox gene mutation?
body parts develop in the wrong place of the body, which results in homeotic mutation
when are hox genes expressed and HOW are they expressed?
they are expressed in early embryonic development ALONG ANTERIOR-POSTERIOR (head-tail) axis of the organism
what is a characteristic observed in genes in the chromosomes and place of the expressed gene?
the order of the genes not he chromosome matches the expression pattern along the embryo,showing spatial linearity
expression of genes can also occur in TEMPORAL ORDER, starting with anterior hox genes expression
spatial linearity and temporal linearity suggest…
COLINEARITY
how do activated genes promote the correct development of each body segments?
regulating mitosis, apoptosis and cell differentiation (some genes are switched on or off, so expressed or not)
what is apoptosis?
programmed cell death
how does apoptosis occur?
1.enzyme break down cell cytoskeleton
2.cytoplasm becomes dense with tightly packed organelles
3.cell surface membrane changes and blebs form
4.chromatin condenses, nuclear envelope break and DNA breaks into fragments
5.cell breaks into vesicles, ingested by phagocytes
what does apoptosis respond to ?
external and internal stimuli such as stress
what can induce apoptosis?and how?
nitric oxide - makes inner mitochondrial membrane more permeable to hydrogen ions and dissipating the proton gradient, protein are released into cytoplasm where they bind to apoptosis inhibitor protein, allowing apoptosis to occur
what does apoptosis cause during limb development? and what can lack of apoptosis during this stage cause?
causes the digits(finger, toes) to separate form each other, lack of apoptosis can cause incomplete separation of two fingers toes.
what does apoptosis cause during development of immune system?
removes harmful and ineffective t lymphocytes.
what does not enough apoptosis lead to?
formation of tumours
what does excessive apoptosis lead to?
cell loss and degeneration
