6.1.1- Cellular Control Flashcards
what is a mutation?
a change in the amount or arrangement of genetic material in a cell
-change in chromosome
-change in nucleotide sequence of a gene
what are spontaneous mutations?
mutations caused by errors during DNA replication or gamete formation
what are inherited mutations?
mutations which are passed on to offspring through gametes
what are induced mutations?
mutations caused by mutagens
what are examples of mutagens?
-mustard gas
-radiation (UV light and X-rays)
-viruses
what is a gene mutation?
the change in nucleotide base sequence which lead to changes in the gene
what are chromosome mutations?
changes in part of chromosome/chromosome number, which occurs during meiosis and are harmful
what are the 4 types of chromosome mutations and what occurs?
-deletion= section of chromosome breaks off
-duplication= sections duplicated
-translocation= section breaks off and joins another non-homologous chromosome
-inversion= section breaks off, is reversed and joins back onto chromosome
what are the 3 point mutations and explain these?
-substitution= one nucleotide pair is replaced by another (missense, nonsense, silent)
-insertion= extra nucleotide base pairs are inserted into a length of dna
-deletion= nucleotide base pairs are deleted from a length of dna
what do deletion and insertion lead to?
a frameshift
what is a missense mutation?
a type of substitution, where the triplet code changes to a code for another amino acid
what is a nonsense mutation?
a type of substitution, where a triplet code for an amino acid changes to a code which instructs translation to stop.
what is a silent mutation?
a type of substitution, where a triplet code changes to a different code for the same amino acid.
what is a frameshift mutation?
where every triplet code after the point of insertion or deletion is altered, making a completely different protein
what is a neutral mutation?
mutations with no selective advantage or disadvantage
what are beneficial mutations?
mutations which increase the chance of survival
what are harmful mutations?
mutations which decrease chances of survival
what is an example of a beneficial mutation?
the peppered moth
what is an example of a harmful mutation?
sickle cell anaemia, mutation in the gene coding for haemoglobin
what is transcriptional control?
when genes can be turned on or off
what two chemicals are involved in chromatin remodelling and what do they do?
-methyl= make the histones more hydrophobic so they pack more tightly to each other
-acetyl= reduces the positive charge of the histones, so they do not coil as tightly
what is heterochromatin?
when the histones are tightly packed, so transcription is not possible as RNA polymerase cannot access genes
what is euchromatin?
when dna is loosely wound so transcription is possible, as RNA polymerase can access genes
what is a transcription factor?
proteins that bind to DNA and switch genes on or off by increasing/decreasing the rate of transcription
what are activators?
transcription factors that increase the rate of transcription
what are repressors?
transcription factors that decrease the rate of transcription
what are inducible enzymes?
some enzymes are only synthesised in response to environmental changes
what are the 3 inducible enzymes created in bacteria/e.coli that are present to metabolise lactose, and what do they do?
-lactose permease= transports lactose into cell
-B-galactosidase= catalyses hydrolysis of lactose into glucose/galactose
-transacetylase= adds acetyl groups to molecules
what is a lac operon?
a length of DNA made up of structural genes, regulatory genes and control sites
what are structural genes?
genes that code for proteins
what are regulatory genes?
genes that code for regulatory proteins which are involved in switching transcription of the structural genes on or off
what are control sites?
the sites where the regulatory protein binds to witch transcription of the structural gene on or off.
what happens in the lac operon when lactose is absent?
1-regulator gene is transcribed and translated to make the repressor protein
-repressor protein binds to operator and blocks promotor
-rna polymerase cannot bind to promotor so structural genes cannot be transcribed
-enzymes are not made, as otherwise this would be a waste of energy.
what happens in the lac operon when lactose is present?
1-lactose binds to repressor protein, which changes shape so no longer binds to the operator
2-rna polymerase binds to promotor so structural genes are transcribed
3-mrna from structural genes are translated
4-cells make the 3 enzymes
what is the post-transcriptional level?
mRNA can be modified, which regulates translation and the types of proteins produced
what is the translational level?
translation can be stopped or started
what is the post-translational level?
proteins can be modified after synthesis which changes their function.
what happens in the post-transcriptional level?
1- a cap (modified nucleotide) is added to the 5’ end and a tail (long chain of adenine nucletides) is added to the 3’ end. This stabilisers the mRNA and delays degradation in the cytoplasm
2- splicing occurs, where the rna is cut at specific points, the introns (non-coding dna) are removed and the exons (coding dna) are joined together
3- rna editing can occur in which some mRNA molecules can also be changed through base addition, deletion, or substitution , can synthsise different proteins with different functions from a single mRNA molecule or gene.
what are the mechanisms of translational control?
1- degradation of mRNA
2- binding of inhibitory proteins to the mRNA preventing it from binding to ribosomes
3- activation of initiation factors which aid the binding of mRNA to ribosomes
what is morphogenesis?
the regulation of the pattern of anatomical development.
what are homeobox genes?
a group of regulatory genes that contain a homeobox, and code for transcription factors that regulate transcription
what is a homeobox?
a section of dna that is 180 base pairs long and codes for a part of the protein that is made up of 60 amino acids
what is the part of the protein that is coded by the homeobox?
homeodomain, that binds to dna and turns on or off genes
why are the homeobox genes similar in plants, animal and fungi?
because they are highly conserved.
why are the homeobox genes similar in plants, animal and fungi?
because they are highly conserved.
what are hox genes?
one group of homeobox gene that are only present in animals
what are hox genes responsible for?
the correct positioning of body parts
in mammal bodies, where are hox genes found?
four clusters on different chromosome
how many hox genes do humans have?
39
how does hox genes aid in the correct position of body parts?
the genes are transcribed in a particular order during development?
what is a good example of where hox genes aid in development?
fly development
what are diploblastic animals?
animals that have 2 primary tissue layers
what are triploblastic animals?
animals that have 3 primary tissue layers
what are somites?
segments in an embryo that are directed by hox genes to develop in a certain way depending on their position in the sequence
what is bilateral symmetry?
organisms have both a left and right side and a head and tail
what is radial symmetry?
seen in diploblastic animals (eg- jellyfish), no left or right, only a top and bottom
what is the role of mitosis in shaping organisms?
increase the number of cells leading to growth
what is apoptosis?
programmed cell death
what is the role of apoptosis in shaping organisms?
removes unwanted cells and tissue
what are the 4 steps to apoptosis?
-hydrolytic enzymes from lysosome released inside cell break down the cytoskeleton
-cytoplasm becomes dense, blebs form on cell surface membrane
-nucleus fragments and cells break into vesicles
-phagocytes ingest the vesicles
what is apoptosis controlled by?
cell signals
