6.1.1 cellular control Flashcards
acetylation/phosphorylation
the addition of acetyl/phosphate groups, to make them more negative so that the DNA can coil less tightly, and transcription can take place
methylation
the addition of methyl groups to make the histones more hydrophobic so that they can bind more tightly to eachother, preventing transcription
epigenetics
used to describe the control of gene expression by the modification of DNA
operon
group of genes that are under the same regulatory mechanism and are expressed at the same time
are operons prokaryotic or eukaryotic
prokaryotic
lac operon
group of 3 genes, lacZ, lacY and lacA, involved in the metabolism of lactose - structural genes
enzymes that the lac operon codes for
B galactosidase, lactose permease and transacetylase
regulatory gene of the lac operon
lacI, codes for the repressor protein which prevents the transcription of the structural genes in the absence of lactose
lac operon when lactose is absent
regulatory gene codes for the repressor protein
attaches to operator site
blocks the promoter site
this means RNA pol cannot attach
structural genes are not transcribed
when lactose is present
a little bit of lactose enters the cell by diffusion
attaches to the repressor protein
this changes the shape of the protein, so cannot attach to operator
RNA pol can attach to promoter
structural genes are transcribed
so enzymes are made
post transcriptional control
splicing
splicing process
pre- mRNA (introns and exons) is then changes when introns are removed and exons are joined, forming mature mRNA
a cap is added on 5’ end and a tail is added on 3’ end for stabilising
spliceosomes
the enzymes involved in splicing, can join the exons in a variety of ways, producing several versions of functional mRNA
factors that regulate when translation starts and stops
- how long the mRNA lasts in the cytoplasm
- inhibitory factors
- initiation factors
post translational control
addition of non protein groups
folding into final shape
activation of proteins by cAMP
cAMP
cyclic AMP, can change the 3D shape of a protein, activating the active
activation of PKA
- PKA is an enzyme with 4 subunits
- when cAMP isnt bound the 4 units are bound together and inactive
- when cAMP binds, it causes a change in the enzymes 3d shape, releasing the active subunits, activating the enzymes
morphogenesis
the regulation of the pattern of anatomical development
homeobox genes
group of genes which all contain a homeobox
homeobox
section of DNA 180 base pairs long coding for a protein which is 60 amino acids long (a homeodomain)
homeodomain
60 amino acids long, and binds to DNA, and switches other genes on and off
hox genes
a group of homeobox genes that are only present in animals, responsible for the correct positioning of body parts
amount of hox genes in humans
39
how body plans are represented
cross sections through the organism showing the fundamental arrangement of tissue layers
somites
the segments in embryo that allow individual vertebrae to be developed, directed by hox genes
radial symmetry
seen in diploblastic animals like jellyfish, no left or right, just top and bottom
bilateral symmetry
seen in most animals means that organisms have both a left and right side and a head and a tail
asymmetry
seen in sponges which have no lines of symmetry
apoptosis
programmed cell death
how apoptosis shapes body parts
removes unwanted cells and tissues
what regulates mitosis and apoptosis?
hox genes
factors affecting the expression of regulatory genes
environment, internal and external
stress and drugs etc
mutation
change in the sequence of bases in DNA or RNA
substitution mutation
mutation in which a single nucleotide changes the codon in which it occurs
degenerate code
multiple codons encode a single amino acid
nonsense mutation
a mutation that changes an amino acid codon to one of the 3 stop codons, resulting in a shorter and non functional protein
missense mutation
a base pair substitution that results in a codon that codes for a different amino acid
insertion mutation
a mutation in which one or more nucleotides are added to a gene
deletion mutation
a mutation in which one or more pairs are removed from a gene
frameshift
mutation that causes the reading frame of mRNA codons to shift (insertion or deletion)
no effect mutation
there is no effect on the phenotype of an organism because the normally functioning proteins are still synthesised
damaging effect mutation
phenotype of an organism is affected in a negative way because proteins are no longer synthesised, which can interfere with essential processes
beneficial effects of mutations
mutations often produce proteins with new or altered functions that can be useful to organism in changing environments
mutagens
physical and chemical agents that interact with DNA to cause mutations
physical mutagens
radiation x rays, UV light (break one or both DNA strands)
chemical mutagens
deaminating agents - chemically alter bases in DNA changing the base sequence
biological mutagens
viruses, base analogs, alkylating agents
chromosome mutation - deletion
due to breakage, a piece of chromsome is lost
chromsome mutation - inversion
a chromosome rearragement in which a segment of chromosome is reversed end to end
chromosome mutation - translocation
a section of one chromosome breaks off and joins another non-homologous chromosome
housekeeping genes
the genes that code for enzymes present in metabolic reactions that are always required
tissue specific genes
the genes that code for protein based hormones which are only required a certain times to carry out short lived responses
the different levels of gene regulation
transcriptional, post transcriptional, translational, post translational
heterochromatin
tightly wound DNA, where RNA pol cannot access the genes
euchromatin
loosely wound DNA where RNA polymerase can access the genes
suggest reasons why fruit flies are chosen for research into genes controlling development of body plan
- fewer public concerns over ethics of using flies
- low cost
- rapid reproduction rate
- fruit fly genetics is understood well
why would mice be used in research of body plans? why not?
- low cost
- similar to humans
- however more ethical concerns
