mod 5 (exam 3) Flashcards
how is mRNA organized and what is it use to create
-organized in codons (3 base chunks)
-used to create the primary structure of a protein (organized into amino acids)
tRNA shape
inverted L-shape with anticodon at bottom and amino acid attachment site at the top
attachment site on a tRNA
-nucleotide sequence CAA
-where amino acids bind so they can be carried by the tRNA
anticodon
-sequence of three bases at the end of tRNA
-each amnio acid has different anticodons, so the tRNA carries the correct amino acid to the complementary codon in the mRNA
ribosome consists of 2 subunits, large and small and
the boundary btw the subunits is the mRNA strand and when translation is not occurring, the subunits separate
when translation is happening, the subunits are together
the ribosome has a ___ where the mRNA enters and then exits after the interior
channel
transcription beings slightly upstream before the genes coding sequence so the mRNAs contain
5’ untranslated region, 5’ UTR before the AUG
in addition to the mRNA, translation imitation requires two other components
1) ribosome, the small subunit
2) a tRNA with the anticodon UAC that is complementary with the AUG in the mRNA that has the methionine amino acid
once the mRNA is bound to the small subunit of the ribosome and tRNA is charges with methionine bound to the start codon in the mRNA,
the large subunit of the ribosome binds to the complex
elongation step one
1) tRNA enters site A if it is anticodon is complementary, the tRNA binds to the mRNA and remains at site A
elongation step 2
2) the amino acid attached to the tRNA in site P and to the tRNA in site A so both amino acids in the machines active site
-peptide bond is formed
-the linked amino acids are held by the tRNA in site A and the amino acid is longer
elongation step 3
3) elongation factors move the mRNA down three bases and moves the mRNA through ribosome to the next codon sequence so it can be translated
-called translocation
after translocation
the uncharged tRNA in site E is ejected from ribosome and the site A opens up and the next codon can enter and bind in the mRNA
guanosine triphosphate (GTP)
-energy to move mRNA through ribosome, same as ATP but its guanosine and not adenosine
with each cycle as the ribosome reads the mRNA in the 5’ to 3’ direction
-another amino acid is added to the growing protein
-the mRNA is moved down a codon
-an “empty” (uncharged) tRNA exits through the E site
-mRNA translocated one codon, and new untranslated codon is available at site A
-tRNA with right anticodon enters in site A and binds and can being the next cycle
when termination occurs, translation ends and
the new protein is released for further modification and the mRNA and ribosome subunits are fee so they can be used again
release factor
when translocation of mRNA binds a stop codon to site A and no tRNA binds so a protein with the same tRNA shape acts with the stop codon and binds to it
ribozyme
RNA molecule that can catalyze specific chemical reactions
mRNAs have a ___ that consists of ____
-reading frame
-a sequence of 3-base-long chunk that functions as codons in RNA or DNA specifying the primary sequence of amino acids in a protein
manufacturing molecules steps
1) the mRNA (temp version of the info) is completed and proteins bind to it and carry it to the nuclear pore and the cytoplasm
2)ribosome uses the info in mRNA to make the primary sequence of the protein
3) it them enters the endomembrane system and undergoes processing and packaging
one a protein is in the ER, the proteins do two key things:
-they remove the signal sequence and help the folding process of the primary sequence into the proteins secondary and tertiary structure
-some proteins in ER add short carbs to the newly folded proteins
proteins leave the ER and go to the
golgi through temporary extensions of tubes from ER to golgi
2 things that happen to proteins and lipids in the golgi
1) may undergo final modifications and have the small molecules attached to the protein (usually a carb) like a bar code to see where it goes
2) they are then sorted into compartments by destination; this sorting occurs when the “bar cods” bind to receptor proteins in membrane of vesicle in golgi sack
after protines and other products leave the golgi
-they are contained in membrane-bound spheres called vesicles (cargo containers) that bud off to the golgi membrane
-then shipped to destinations around the cell
how to vesicles get to their destination?
1) exterior of each vesicle has proteins like zip cods for a destination
2) motor proteins walk along microtubule tracks
motor protein
protein that functions in cell movement through shape changes on if it is phosphorylated or dephosphorylated
signal sequence
a series of amino acids at the start of a protein that allows the protein to enter the endomembrane system
endomembrane system
collection of machines, cytoskeletal components, and organelles that produce, process, and transport proteins and lipids for their desired destination of the organelle, cell membrane, or outside the cell
mutation
any change in DNA or change in genetic information
mutations that occur in germline cells end up in
sperm or eggs and are passed to the next generation
mutations in somatic cells are passed
to daughter cells if and when they divide, can carry new mutations after mitosis
three main sources of mutatoins
1) errors that occur when DNA is being copied prior to mitosis or meiosis
2) physical or chemical damage to DNA
3) errors that occur as chromosome are being moved during mitosis or meiosis
errors in DNA rplication
sometimes the DNA polymerase inserts a mismatched based in a strand and the mismatched bases can slip through proofreading and give rise to new mutations
DNA damage
-changes to the DNA from damage can have small, single-base impacts, or large changes in large segments of a chromosome
Mistakes during meiosis or mitosis
-can cause DNA change in whole chromosomes or even at haploid(1) or diploid(2) chromosomes
four types of mutations
1) missense
2) nonsense
3) silent
4) frameshift
missense mutations
-changes in a single base that can lead to a change in the mRNA codon and amino acid protein product
nonsense mutations
-changes in a single base that changes a codon of an amino acid into a stop codon
-meaning translation stops early and the primary sequence of the protein product is a fraction of its normal length
silent mutations
-changes in a single base that leads to a change in the resulting mRNA codon but no change in the amino acid protein product
-silent mutations occur b/c of redundancy in genetic code
frameshift mutations
-changes in one or more bases that lead to a change in the reading frame of codons read by the ribosome during translation
-the codons in the 3’ direction are shifted and the protein changes
meiosis creates genetic varication in offspring by
mixing and matching maternal and paternal chromosomes as the line up at random in the middle f the cell into the daughter cell
mutations in somatic cells are
not passed onto offspring
deleterious mutation
any mutation that decreases fitness; lead to an early death are are termed lethal
what does a gene need to do?
1) it needs to carry info
2) it needs to be stable
3) it has to be copyable
DNA has to be ___ every time the cells in your body divide
copied
for DNA synthesis to occur
enzymes need to catalyze formation of phosphodiester linkages b/w deoxyribonucleotides that are complementary to an existing or template strand
rules for synthesizing a new complementary strand of DNA
1) occurs in the 5’ to 3’ direction, so new bases are added to the 3’ of an existing strand
2) DNA polymerase only adds new bases to the 3’ end of an existing complementary strand of DNA from scratch
3) when DNA replication occurs, gaps from b/w end of new segments (gap in the sugar-phosphate backbone b/w 2 adjacent nucleotides)
when making a phosphodiester bonds, filling gaps requires a DNA ligase that
does not extend the sugar-phosphate backbone by adding new bases to the 3’ end of a growing strand
DNA polymerase
enzyme that builds new DNA strands
-catalyzes the formation of phosphodiester linkages btw deoxyribonucleotides, forming the primary structure of the DNA
origins of replication
places where DNA replication starts
primase
-enzyme that synthesizes a short sequence of RNA complementary to the DNA on the top strand
-adds a short RNA primer to a ssDNA so DNA polymerase can add complementary bases
RNA primer
-“primes” the strand for the DNA polymerase
-can start synthesis from scratch on a single stranded template strand
leading strand
strand that is synthesized toward the replication fork
as the RNA polymerase starts a new strand from scratch, the DNA polymerase then
starts adding complementary deoxyribonucleotides to create the lagging strand (lags behind the leading strand)
helicase
enzyme that “unzips” DNA, breaking the hydrogen bonds btw complementary pairs to create ssDNA
topoisomerase
breaks and rejoins RNA ahead of the replisome, to relieve the twisting force created as the helicase unzips the double helix
replisome
multi-molecular machine that works at the replication fork, copying DNA
replication fork
-the y-shaped structure visible in micrographs of DNA during replication.
- the site where the replisome works, synthesizing the leading and lagging strands
cancer
family of diseases that have uncontrolled cell division
uncontrolled cell division produces a mass called a
tumor
3 reasons cancers are complex diseases
1) cells divide uncontrollably
2) attachment sites are off so they don’t stay in one place
3) when cells are dividing rapidly, a tumor cells could gain the ability to stimulate growth and continue the cancer development
cell cycle G1
-first gap
-the gap grows, meaning the organelles are replicated
-high rates of translation and transcription
-receives signals to keep growing and dividing or to stop diving
G0
-long term, non-dividing state
cell cycle S
if cells in G1 need to grow more
-S phase, replicate the chromosomes, synthesizing DNA
G2 in cell cycle
-chromosome replicated and cell keeps growing
-lays the ground work for mitosis and cell division
M in cell cycle
-mitosis
-cell division for 2 daughter cells and then daughter cells enter the G1 phase
G1 checkpoint requirements
-only can pass the check point if they receive signals to keep them in the dividing state
-they are being supplied with nutrients to grow
-DNA not damaged
G2 checkpoint
-regulatory proteins check to see if all chromosomes have been replicated without damaged DNA
M check point
-regulatory proteins asses if the microtubules that pull the sister chromatids apart are attached properly and that the chromatids have separated so each daughter cell only gets one chromosome
metastasis
process of tumor cells breaking away from a tumor, traveling to new locations and making new tumors
tumor supressors
genes whose protein products function as regulatory molecules at cell checkpoints, preventing uncontrolled division of damaged cells
what serves as a template strand during the copying process?
the original strands of the replicating chromosome 1 itself
replication starts at the origin of replication in the ____ direction
5’ to 3’
newly synthesized strands are added on the
3’ end
exonuclease
-removes nucleotides from END of DNA strand
-used in proofreading
endonuclease
-removes nucleotides from MIDDLE of DNA strand
-used during mismatch repair after replication is finished
G1, G2, and S phase are all part of
interphase
