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104 Cards in this Set
- Front
- Back
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alternative RNA splicing |
a post-transcriptional gene regulation mechanism in eukaryotes in which multiple protein products are produced by a single gene through alternative splicing combinations of the RNA transcript |
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codon |
three consecutive letters in mRNA that specify the addition of a specific amino acid or the release of a polypeptide chain during translation |
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DNA ligase |
the enzyme that catalyzes the joining of DNA fragments together |
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DNA polymerase |
an enzyme that synthesizes a new strand of DNA complementary to a template strand |
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deoxyribose |
a five-carbon sugar molecule with a hydrogen atom rather than a hydroxly group in the 2' position; the sugar component of DNA nucleotides |
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double helix |
the molecular shape of DNA in which two strands of nucleotides wind around each other in a spiral shape |
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epigenetic |
describing non-genetic regulatory factors, such as changes in modifications to histone proteins and DNA that control accessibility to genes in chromosomes |
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exon |
a sequence present in protein-coding mRNAafter completion of pre-mRNA splicing |
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gene expression |
processes that control whether a gene is expressed **the process of turning on a gene to produce RNA and protein |
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genetic code |
the amino acids that correspond to three-nucleotide codons of mRNA |
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helicase |
an enzyme that helps to open up the DNA helix during DNA replication by breaking the hydrogen bonds |
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intron |
non-protein-coding intervening sequences that are spliced from mRNA during processing
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lagging strand |
during replication of the 3' to 5' strand, the strand that is replicated in short fragments and away from the replication fork |
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leading strand |
the strand that is synthesized continuously in the 5' to 3' direction that is synthesized in the direction of the replication fork |
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mRNA |
messenger RNA: a from of RNA that carries the nucleotide sequence code for a protein sequence that is translated into a polypeptide sequence |
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mismatch repair |
a form of DNA repair in which non-complementary nucleotides are recognized, excised, and replaced with correct nucleotides |
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mutation |
a permanent variation in the nucleotide sequence of a genome **permanant change in DNA sequence - can lead to cancer |
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nitrogenous base |
a nitrogen-containing molecule that acts as a base - often referring to one of the purine or pyrimidine components of nucleic acids |
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nontemplate strand |
the strand of DNA that is not used to transcribe mRNA - this strand is identical to the mRNA except that T (thymine) nucleotides in the DNA are replaced by U (uracine) nucleotides in the mRNA |
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nucleotide excision repair |
a form of DNA repair in which the DNA molecule is unwound and separated in the region of the nucleotide damage, the damaged nucleotides are removed and replaced with new nucleotides using the complementary strand, and the DNA strand is resealed and allowed to rejoin its complement |
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Okazaki fragments |
the DNA fragments that are synthesized in short stretches on the lagging strand |
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phosphate group |
a molecular group consisting of a central phosphorous atom bound in four oxygen atoms |
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post-transcriptional |
control gene expression after the RNA molecule as been created but before it is translated into a protein |
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post-translational |
control of gene expression after a protein has been created |
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primer |
a short stretch of RNA nucleotides that is required to initiate replication and allow DNA polymerase to bind and begin replication |
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promoter |
a sequence on DNA to which RNA polymerase and associated factors bind and initiate transcription |
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RNA polymerase |
an enzyme that synthesizes an RNA strand form a DNA template strand |
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rRNA |
ribosomal RNA: molecules of RNA that combine to form part of the ribosome |
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replication fork |
the Y-shaped structure formed during the initiation of replication |
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semiconservative replication |
the method used to replicate DNA in which the double-stranded molecule is separated and each strand acts as a template for a new strad to be synthesized, so the resulting DNA molecules are composed of one new strand of nucleotides and one old strand on nucleotides |
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splicing |
the process of removing introns and reconnecting exons in pre-mRNA |
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start codon |
the AUG (or rarely, GUG) on an mRNA from which translation begins, always specifies methionine |
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stop codon |
one of three mRNA codons that specifies termination of translation |
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tRNA |
transfer RNA: an RNA molecule that contains a specific three-nucleotide anticodon sequence to pair with the mRNA codon and also binds to a specific amino acid **type of RNA molecule that brings amino acids to the growing chain of the polypeptide |
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telomerase |
**an enzyme that contains a catalytic part and an inbuilt RNA template, it functions to maintain telomeres at chromosome ends **attaches to the end of the chromosome and complementary bases to RNA template are added so the lagging strand template is complete and the DNA polymerase can finish synthesis of lagging strand |
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telomere |
the DNA at the end of linear chromosomes (contain repetitive sequences that do not code for a gene) |
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template strand |
the strand of DNA that specifies the complementary mRNA molecule |
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transcription bubble |
the region of locally unwound DNA that allows for transcription of mRNA |
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What does DNA stand for?
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Deoxyribonucleic acid
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DNA can be retrieved from?
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Hair, blood, saliva
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What is DNA?
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The genetic material passed from parent two offspring for all living organisms
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molecular genetics (aka biotechnology)
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The study of DNA and the inner workings of a cell
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Francis crick and James Watson
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Determined the structure of DNA in the 1950s
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Xray crystallography
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Methods for investigating molecular structure by observing the patterns formed by xrays shot through a crystal of the substance
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Chargaff's rules |
Chargaff up up had shown that of the four kinds of monomers (nucleotides) present in the DNA molecule, two types were always present in equal amounts and the remaining two types were always a present an equal amount meaning they were paired in some way |
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Ribonucleic acid
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RNA
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What does the DNA nucleotide consist of? (3 components)
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1. deoxyribose (5-carbon sugar) 2. a phosphate group 3. nitrogenous base |
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What are the four nitrogenous bases in DNA?
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PURINES (double ringed) A - adenine G - guanine PYRIMIDINES (single ringed-smaller) C - cytosine T - Thymine |
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What is the formation of a DNA nucleotide? |
Double helix
Phosphate group on the outside - connected to Deoxyrbose molecules - connected to Nucleotide on the inside The phosphate connects to the next Deoxyribose in line and so on until all the nucleotide mononmers form a long polymer chain |
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What makes the DNAs backbone?
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sugar-phosphate groups held together by hydrogen bonds |
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Carbon atoms of the 5' carbon sugar are numbered...
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Clockwise starting AFTER the oxygen as 1', 2', 3', 4', 5'
1' is read as one prime 4' and 5' are on the same "point" (4' on the interior and 5' on the outside) |
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The phosphate group is attached to...
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the 5' carbon of one nucleotide and the 3' carbon of the next nucleotide on the opposite side (other rung of double helix ladder) |
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DNA is held together by....
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Hydrogen bonds
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purines are paired with pyrimidines (complementary base pairs - Chargaff's rule)
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A - purine T - pyrimidine G - purine C - pyrimidine |
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A and T connected by... |
two hydrogen bonds |
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C and G connected by... |
three hydrogen bonds |
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What is anti-parellel in structure |
the individual strand of DNA that form the double helix. One strand will have the 3' carbon of the sugar upward while the opposite strand has the 5' carbon of the sugar in the upward position |
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RNA |
similar to DNA - is a polymer of nucleotides. only difference is that the sugar is RIBOSE and all of the T (thymine) is replaced by U (uracil) |
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What is the structure of the sugar molecule in RNA? |
Ribose - clockwise beginning after Oxygen point 1' - hydroxyl 2' - hydroxyl (differs from DNA sugar) 3' - hydroxyl 4' - hydroxyl (interior, point shared by 4' & 5') 5' - CH2 |
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What is the structure of the sugar molecule in DNA? |
Deoxyribose - clockwise beginning after Oxygen point 1' - hydroxyl 2' - hydrogen (differs from RNA sugar) 3' - hydroxyl 4' - hydroxyl (interior, point shared by 4' & 5') 5' - CH2 |
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What is the difference between the sugar molecule in RNA and DNA? |
DNA - Deoxyribose RNA - Ribose At the 2' point of the molecule deoxyribose has hydrogen, while ribose has a hydroxyl |
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What is the goal of cellular division? |
Cell replicates DNA and divides into two identical daughter cells |
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DNA replicates when? |
Replicates during synthesis (S phase) of the cell cycle before cell begins mitosis or meiosis |
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DNAs separate strands are complementary, why is that necessary? |
because a/t pairs and c/g pairs the strands can be used as a template to recreate the opposite strand. When replicated there will be a newly formed daughter strand that is paired with the template or parent strand (semiconservative replication) |
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Stages of DNA Replication |
initiation elongation termination |
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DNA is tightly compressed and spooled around? |
histone proteins |
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When DNA is bound to histones it forms |
nucleosomes |
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Initiation |
first step in DNA replication: **specific proteins bind to the origin of replication **helicase enzyme unwinds/opens DNA helix by breaking the hydrogen bonds **Y-shaped stucture (replication forks) are formed as DNA opens in both directions from origin (like a bubble) |
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origin points on eukaryotic chromosomes |
are in multiple locations so replication can occur simultaneously from several places in the genome |
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Elongation |
2nd Stage in DNA replication: **Primer sequence is placed by RNA nucleotides to provide start position for... **DNA polymerase adds DNA nucleotides to 3' end of the template and sythesizes the 5' to 3' strand continuously **3'- to 5' strand is synthesized in short pieces (Okazaki fragments), the DNA polymerase needs RNA primers to initiate each section |
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Termination |
3rd stage in DNA replication:
**RNA primers are removed and replaced with DNA nucleotides **The DNA backbone is resealed by the DNA ligase enzyme |
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Telomeres have/why is it important |
repeated sequences that don't code for a gene, **it's important because on the lagging strand the chromosome would get shorter and shorter because there is no place for a primer to be made for the DNA fragment **instead of nucleotides for genes getting shortened (which would be all kinds of bad) these get shortened instead and maintains genetic integrity |
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Elizabeth Blackthorn |
discovered telomerase and it's actions, Telomerase is typically found in germ cells, adult stem cells and some cancer cells, BUT not active in all adult somatic cells. She received Nobel prize in 2009 |
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somatic cell telomeres |
are shortened and synonomous with aging, telomerase is not active in somatic cells generally |
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Prokaryotic chromosomes are and replication occurs: |
**circular with less coiling than eukaryotic chromosomes **replication begins at a single origin point and moves around whole chromosome **replication is much more rapid in prokaryotes **Prokaryotes have no telomerase |
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DNA repair |
**DNA polymerase makes mistakes but is proofreading as it works and removes incorrectly placed bases and replaces it with the correct base during replication **Mismatch repair - specific enzymes recognized mistakes and excise the errors from the DNA and the correct bases are placed **Nucleotide excision repair - DNA strand is unwound/separated and incorrect bases removed with some on the 5' and 3' end and replaced by DNA polymerase |
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Thymine dimers |
two thymine nucleotides adjacent to each other and bonded versus bond with its complimentary base (A), often caused by UV light exposure **if not repaired it will lead to mutation (skin cancer) |
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Central Dogma |
DNA makes RNA makes Proteins *genes (DNA) specify sequence of mRNA during transcription *mRNA take that info and specify sequence for proteins during translation |
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Transcription |
3 stages (same as DNA replication) Initiation Elongation Termination |
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Transcription initition |
*DNA helix unwinds at "transcription bubble" *the "promoter" is the location transcription is initiated by specific enzymes/proteins |
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Transcription elongation |
*always works off of the 3' to 5' strand (template strand) so mRNA is constructed 5' to 3' *RNA polymerase reads DNA template strand and adds complimentary nucleotides (except T will be U) *mRNA strand is not bound and as it is synthesized the DNA helix is opened in front of it and closed behind it (transcription bubble moves along DNA helix) |
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Transcription Termination in prokaryotes |
RNA polymerase instructed to disassociate from DNA template and let go of mRNA strand - by the time transcription is completed the mRNA strand would have already begun synthesizing the protein(s) because there is no nucleus to contend with *less stable than eukaryotic mRNA |
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Transcription termination in eukaryotes |
*coated in RNA-stabilizing proteins to prevent degradation by adding a cap to the 5' end (used to initiate translation) *string of about 200 adenine is added to 3' end (called poly-A tail) *pre-mRNA introns are removed and exons are connected *poly-A tail guides mRNA out of nucleus through a pore to ribosome |
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Ribosome |
**complex macromolecule composed of structural and catalytic rRNAs and many distinct polypeptides **located in cytoplasm and endoplasmic reticulum **rRNAs synthesized in nucleolus |
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how many tRNAs are in the cytoplasm? |
40-60 depending upon species |
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codons are attached to |
mRNA |
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anticodons are attached to |
tRNA |
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how many different kinds of amino acids are there and where are they stored until being used for protein synthesis (translation) |
There are 20 different types of amino acids stored in the cytoplasm until used in translation or whatever else is specified within the cell |
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using a 3-nucleotide code means there are... |
64 (4x4x4) possible combinations and certain amino acids are represented by more than one nucleotide code |
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How many codons terminate translation? |
Three - known as "stop codons" |
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tell me codon info to initiate translation..
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One start codon (AUG) also represents the amino acid methionine |
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Where does translation begin? |
near the 5' end of the mRNA |
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Translation process (protein synthesis) |
Three stages: Initiation Elongation Termination |
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Translation Initiation |
*tRNA interacts with AUG start codon and links an amino acid to begin the polypeptide chain, which is removed once translation is completed |
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Translation Elongation |
*Within the ribosomal subunit: -"A" site binds incoming tRNAs (w/ anticodons) -"P" site binds charged tRNAs and pairs anticodons to mRNA codons -"E" site releases disassociated tRNAs to recharge with available amino acids *Between the 3 sites ribosome shifts one codon at a time, catalyzes the process in all 3 sites and the polypeptide chain grows |
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What is the energy that "charges" tRNA |
GTP (molecule similar to ATP) |
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Translation Termination |
**translation ends when a stop codon is encountered (UAA, UAG, UGA) *polypeptide chain is released *ribosome subunits disassociate *mRNA broken down to be reused for another transcription |
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cells in different tissues |
perform different functions because of differing sets of genes being expressed in those specific cells |
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cellular response to changes in environment or development |
turn on and off specific genes |
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malfunction of gene control (expression) ... |
detrimental to cellular integrity and can lead to disease, including cancer |
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transcription and translation occur almost simultaneously... |
in prokaryotes...no nucleus |
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prokaryotic gene expression occurs when |
*at the transcription level
*promoter and operator perform transcription when energy source is available *when no energy source a repressor binds the operator so transcription cannot occur |
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lac operon |
stretch of DNA w/ 3 adjacent genes that code for proteins that participate in the absorbtion and metabolism of lactose |
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eukaryotic gene expresion regulation |
can occur during any stage of transcription or translation because the processes occur in physically separate areas (nucleus vs. cytoplasm) |
