Gene expression AND regulation Flashcards
genetic info is permanently stored in
DNA
transcription:
copies genetic info from DNA to RNA (converting info into a different form without changing the information)
Info is temporarily stored in RNA
translation
coverts genetic information in RNA to a protein (info is turned into different thing)
Protein perform some function
RNA stands for
ribonucleic acid
RNA is similar to DNA but
has ribose sugar instead of deoxyribose
RNA can base pair with DNA but…
RNA uses U instead of T to pair with A
RNA base pairs:
C and G
A and U
backbone of RNA
ribose
why is RNA single stranded
its main function is to USE info, not store it. so the one strand makes it more easily accessible.
where are codons located
DNA and RNA
if nucleotides are like letters, codons…
are the words of all living things (spelt by nucleotides)
codons function
translate info in DNA to proteins that we ultimately want
codons code for
specific amino acids
triplet code
3 nucleotide sequence that is code for one of 20 amino acids
____ total codons
64 total
61 code for amino acids
3 are stop codons
what is the start codon?
AUG (also codes for methionine)
redundancy is often seen in the __ letter of the codon wheel thingy
last
a given amino acid can be coded for by …
more than 1 codon
codons are/are not evenly distributed between amino acids?
are not
what aspect of codons reduces effect of mutations ?
the redundancy (64 codons for only 20 amino acids)
mRNA
copied from DNA
rRNA
-forms ribosomes
-provides location for tRNA to pair with mRNA and hangs on to growing proteinn
tRNA:
-carries amino acids to ribosome
-translates genetic code into amino acids
-anticodons are complementary to mRNA codons
exons
useful parts of mRNA
introns
unused parts of mRNA
RNA splicing
removes introns and connects exons
RNA can code protein domain:
protein pieces that provide new function
combine domains to create new cellular machines
mutations are ___ errors
uncorrected
mutations can arise from
Wrong base
Missing base
Extra base
mutations alter
instructions in DNA
point mutation
one changed nucleotide
-Can change amino acids in proteins
*Altered protein may have a different 3D shape
*Altered protein may not be able to do its job as well
neutral/silent mutation
has no effect on protein
silent mutation: purpose of redundancy
May sub a chemically similar amino acid so that protein still makes the same shape and therefore function
frameshift mutation
inserting or deleting nucleotides
Very bad
3 nucleotide codon sequence is off
Creates nonsense genes
Often results in an early stop codon
differential gene expression
changing what proteins are being made
cell function is based on
what genes are being used
gene expression: whether a gene is
turned off or not (can be a gradient)
gene expression can be controlled at different steps:
- DNA packing
- Transcription
- RNA processing and breakdown
- Translation
- Protein processing and breakdown
chromatin
DNA + proteins holding it
DNA is wrapped around
histones:
* Histone tails stabilize DNA
* Creates nucleosome
RNA polymerase splits and unwinds DNA to copy it, but…
DNA can be tightly coiled on histones
Tightly coiled DNA leaves no room for RNA polymerase
* Gene may be coiled up
* Promoter may be coiled up
* Gene is inactivated
No proteins from inactivated genes
histone modification affects ___ availability
DNA
histone methylation
DNA is wrapped tightly and is unavailable
histone acetylation
DNA is rapped less tightly and is available
what helps control transcription?
transcription factors
general transcription factors:
needed for all genes
specific transcription factors
control specific genes
activators vs repressors
- Activators increase transcription
- Repressors decrease transcription
gene control elements organize
transcription factors
where are gene control elements?
in non-coding DNA
enhancers:
group of gene control elements
alternative RNA splicing
different portions of instructions can be kept or removed
one pre-mRNA can code for
multiple proteins (spliced differently for each)
pre-mRNA:
mRNA without introns removed
_____ molecules can block translation of specific mRNA
regulator (specific protein is not made)
deactivating ribosomes
controls translation of ALL mRNA (no proteins are made)
when are deactivating ribosomes useful?
when a virus is present
inheritance patterns are NOT caused by
order of DNA nucleotides
epigenetics
study of non-sequence DNA changes
epigenetic
how cells control gene activity without changing the DNA sequence.
epigenome:
all the epigenetic changes that have happened to ur DNA
DNA methylation is an example of epigenetic change:
methyl group attached to DNA due to life experiences, prevents some genes from being expressed.
methylation is a gradient:
o Can have more or less methylation and it will either be transcribed more or less
o Like a dimmer switch
____ cells can become anything
embryonic
as body develops, cells ____.
differentiate: become specialized and can no longer become everything
epigenetics and cancer: some genes are unmethylated
o Turned on
o More transcription than normal
o Genes that promote cell growth and division
epigenetics and cancer: some genes are strongly methylated
o Turned off
o Genes that stop cell growth
o Genes that repair DNA
o Genes that help cell kill itself
epigenetics and daughter cells:
- Cells divide to form daughter cells
- Cells pass on experiences to daughter cells
o Daughter cells are prepared for similar experiences - New DNA is methylated
o Teaches new cell what environments are like
only ____ of human genome codes for proteins
1.5%
even though only 1.5% of DNA makes proteins…
about 75% of DNA is transcribed at some point, making noncoding
even though only 1.5% of DNA makes proteins…
about 75% of DNA is transcribed at some point, making noncoding RNA that controls whether proteins are made or not
microRNA and small interfering RNA regulates translation of
specific mRNA
-bind to mRNA
-block translation or tag for destruction
how are cancer cells different?
1. They divide when they should not
2. They invade surrounding tissues
3. They move to other locations
mRNA
copied from DNA
long noncoding RNA
packages DNA more tightly in chromosomes
involved in X inactivation
cell cycle control system coordinates
key events in cell cycle
cell cycle control system generates its own
cell cycle control system stops at checkpoints:
-Control point to ensure conditions are right for continuing cycle
* G1
* G2
* Metaphase
cell cycle control system checkpoints are regulated by
proteins
mutations in cell cycle control system regulating proteins may lead to
unregulated cell cycle (can lead to tumors and cancer)
porto-oncogenes:
genes which promote cell division
porto-oncogenes can be mutated to form
oncogenes (cancer genes)
tumor suppressor genes:
stop cell division if conditions are unfavorable
tumor supressor genes help regulate
cell cycle checkpoints
mutations in DNA repair genes
-Reduces ability to correct mistakes
* Can dramatically increase rate of new mutations
agiogenesis
:stimulatesformationof new blood vessels to give cancer nutrients
more than one _____ to form cancer cells
mutations needed
some types of mutations that cancer needs:
- Inactivation of tumor suppressor genes
- Inactivation of DNA error checking and
repair - Proto-oncogenes into oncogenes
- Loss of contact inhibition: cells divide even when in dense groups
- Loss of anchorage dependence: cells divide when not attached to anything
- Reactivation of telomerase enzyme
ways to detect cancer:
-Find denser tissue
* Proteins in blood
* Biopsy: examine surgically removed cells
chemotherapy
Injected chemicals selectively kill dividing cells
radiation
High-energy particles used to damage DNA and kill cancer cells
