genetics Flashcards
(96 cards)
1
Q
genes in DNA are copied into a new format RNA
A
Transcription
2
Q
protein synthesis also known as ? is where genetic info w/in a cell is read and used to create gene products-proteins.
A
gene expression
3
Q
reading mRNA to build proteins
A
translation
4
Q
transcription makes RNA in 3 steps. What are they?
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- Initiation. 2 Elongation 3 Termination
5
Q
what’s the first step of transcription?
A
RNA polymerase binds to the promoter and DNA unwinds, revealing the template strand.
6
Q
what’s the second step of transcription?
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RNA polymerase travels down the DNA. The RNA is built from 5’ to 3’ as complementary ribonucleotides are paired with the template strand.
7
Q
What the third step of transcription
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a termination sequence at the end of the transcribied gene signals the RNA polymerase to fall off the DNA and release the new RNA.
8
Q
while genetic info usually flows just one way some cells and viruses can carry out ? which uses RNA as a template to build copy DNA (cDNA).
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reverse transcription
9
Q
carry out reverse transcription
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reverse transcriptases
10
Q
mostly linear molecules carry out the genetic messages stored in DNA..
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messenger RNA (mrna)
11
Q
messenger RNA is encoded in triplets of nucleotides ?
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codons
12
Q
Codon are only found in messenger rna t/f
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t
13
Q
Codons consist of ?
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A,U,G,C and each codon specifies either an amino acid or a stop signal that ends translation.
14
Q
These clovershaped RNA molecules bring the correct amino acid to a ribosome to build proteins.
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transfer RNA (tRNA)
15
Q
The ? located toward the lower portion of the TRNA is complementary to a codon on mRNA. This ensures that the proper amino acid is being brought into the ribosome to be added to the growing protein chani.
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anticodon
16
Q
these RNA molecules fold up into elaborate three dimensional structures and combine with proteins to form ribosomes.
A
Ribosomal RNA (rRNA)
17
Q
what’s the function of a ribosomal RNA
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they help ribosomes read or scan an mRNA molecule and fomr peptide bonds between amino acids to build a protein.
18
Q
This involves clipping out certain sequences in RNA and joining the remaining parts of the molecule.
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RNA spicing
19
Q
In eukaryotic cells only certain segments of mRNA are decoded to build a protein these coding sequences are called
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exons
20
Q
The intervening sequences in mRNA that are not decoded to build proteins. In e and p. cells
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introns.
21
Q
mRNA editing is performed in the nucleus by a complex called the ?
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spliceosome
22
Q
what is the ribosomes structure
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two subunits a large and a small subunit.
23
Q
what does the ribosome perform?
A
translation
24
Q
what’s step one of translation?
A
ribosome attaches to mRNA and scans unit it reaches a start codon (AUG). Initiator tRNA carrying amino acid methionine then enters the ribosome’s p site.
25
what's the second step of translation
incoming tRNA enters A site. peptide bonds form between amino acids transferring growing proteins to tRNA in A site. Ribosomes translocates (shifts) down mRNA? tRNA in P site shifts to E site to exit ribosome; trRNA in the A site shifts to P site.
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what's the third step of translation?
Ribosome encounters stop codon. Termination factor enters the ribosome. Ribosome releases the protein and detaches from mRNA.
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These are often required for a protein to function and provide a way for cells to regulate gene product functionality.
post-translational modifications
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allows cells to control gene expression by regulating how much mRNA is made from a given gene examples
pre-transcriptional regulation operons, quorum sensing, epigenetic control, recruitment of transcription factors
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allows cell to control gene expression by regulating how often mRNA is translated into protein examples
post transcriptional regulation; recruiting ribosome to mRNA, riboswitches, small noncoding RNA's, controlling mRNA stability, eukaryotes also can control RNA processing and nuclear export (not used in prokaryotes)
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where does translation occur in eukaryotic cells
cytoplasm
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where does translation occur in prokaryotic cells
cytoplasm
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typically less than 20 percent of a cells genes are expressed at any given time. some are used for everyday cell work and are referred to as
house keeping genes
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these genes encode proteins that are reliably found in a cell and are
constitutive genes
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are made selectively when a cell encounters a specific environmental change, or has a special job to do
facultative
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helps cells control when and how often transcription occurs.
pre-transcriptional regulation
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specialized proteins that bind to DNA and help recruit RNA polymerase to start transcription.
transcription factors
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a collection of genes controlled by a shared regulatory element.
operon
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operons include four key parts that combine to make an on off switch to regulate transcription.
1 a promoter, which RNA polymerase associates with transcription. 2 two or more genes that work together toward a shared task. 3 a repressor that blocks transcription and 4 an operator the part of the operon that the repressor binds in order to block transcription.
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are off by default unless certain conditions arise under which they are activated (induced) to allow transcription.
inducible operons
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are on by default, meaning they are actively transcribed until they are switched off (repressed)
repressible operons
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an example of an inducible operon is
lactose operon of E. coli this operon is induced , or actively transcribed only when lactose is present and glucose is absent.
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An example of a repressible operon is
arginine operon which regulates the production of the amino acid arginine. the arg operon is by default transcribed (is always on ) unless the repressor gains the ability to bind to the operator.
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all the chemical changes to the genome
epigenome
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epigenetic regulation is a way to control protein synthesis by directly altering the appearance of DNA without changing it's sequence. one way e. and p. cells do this is by ? which involves adding methyl groups to DNA
DNA methylation
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The collective sensing and responding to changes wihtin a bacterial community is called This allows bacteria to alter their protein synthesis in response to changes in the density of the population.
quorum sensing
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? regulation impacts how often mRNA is translated into protein.
post transcriptional regualtion
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these impact protein synthesis
small noncoding RNA's
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certain mRNA's have built in switches that act as protein synthesis controls. These ? are not translated into protein
riboswitches
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mutations that do not change the amino acid sequence of a protein are called
silent mutations.
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A ? is a change in the genetic material of a cell or virus.
mutation
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occur when an incorrect nucleotide is added—
substitution mutation
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occur when a cell adds one or more nucleotides to its genome sequence.
Insertion mutation
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occur when one or more nucleotides are removed from a genome sequence.
deletion mutation
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the new codon encodes the wrong amino acid
missence mutation
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occurs if the change leads to a stop signal instead of an amino acid.
nonsense mutation
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a base-substitution mutation can be corrected by another base substitution; in effect, the error is corrected by another error
reversion mutation
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A mutation that causes a codon to go from encoding an amino acid to encoding a stop signal is called a
nonsense mutation
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in which the meaning of the codon is changed in a way that the wrong amino acid is added to the growing protein, is far more common.
missence mutation
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Inserting or deleting bases from the coding region of a genetic sequence results in a
frameshift mutation
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The impact of insertions and deletions is minimized if these mutations
occur in multiples of three
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Naturally occurring mutations are often referred to a
spontaneous mutations
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are chemical, physical, or biological agents that increase the rate of mutation.
mutagens
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include organic or inorganic agents. These agents cause mutations by a variety of methods, such as inducing breaks in DNA, modifying bases, or promoting frameshift mutations by directly inserting themselves into the DNA. Examples of chemical mutagens include arsenic, asbestos, alcohol, and a variety of compounds in tobacco smoke
chemical mutagens
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induce DNA damage similarly to how chemical mutagens do, but they include radiation such as ultraviolet (UV) light, X-rays, and radioactive gamma rays.
physical mutagens
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are agents that can introduce genetic change through recombination
Biological mutagens
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which is an exchange of genetic material that leads to new genetic combinations.
recombination
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Many mutagens cause a rate of mutation that promotes the development of cancers; such mutagens are called
carcinogens
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was developed to quickly identify mutagens that alter DNA by either base substitutions or by frameshift mutations. It relies on strains of Salmonella typhimurium bacteria that cannot make the amino acid histidine (called his− strains).
The Ames test
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specialized enzymes clip out damaged or mismatched nucleotides, and then DNA polymerase I lays down new nucleotides to repair the DNA. The enzyme ligase, which was used to glue Okazaki fragments together in DNA replication, also glues the nicks in the DNA sugar–phosphate backbone, so that the repair patch is seamless (Fig. 5.21)
excision repair
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Excision repair is especially active in fixing ? damage in DNA.
UV radiation
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occurs when cells pass their genetic information to the next generation (from parent cell to offspring) as a result of sexual or asexual cell division.
Vertical gene transfer
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passes genetic information between cells by a process independent of cell division, and therefore separate from reproduction.
horizontal gene transfer
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are nonchromosomal DNA segments found in bacteria and a number of eukaryotic cells; they are commonly shared among cells by horizontal gene transfer mechanisms.
plasmids
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a bacterium that carries a fertility plasmid forms a small hollow tube called a pilus, which attaches to a neighboring bacterial cell that lacks a fertility plasmid. The pilus serves as a bridge for transferring a copy of the fertility plasmid to the cell lacking it (Fig. 5.22 left). Then the pilus is dismantled and the cells separate. Assuming a complete copy of the fertility plasmid transfers, the recipient cell can then initiate ? with cells that lack fertility plasmids.
conjugation
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horizontal gene transfer process is called ?. Here bacteria are genetically altered when they take up DNA from their environment
transformation
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Griffith's experiment
First Griffith infected mice with a living strain of S. pneumoniae that tends to be dangerously virulent due to its capsule. (See Chapter 3 for more on capsules.) As expected, the mice infected with the live encapsulated S. pneumoniae died.
Next, Griffith infected mice with a nonvirulent, living strain of S. pneumoniae that does not make a capsule. Again, he got expected results: The mice remained healthy.
In the third scenario, he infected mice with heat-killed, encapsulated S. pneumoniae. Because the pathogenic bacteria were dead, Griffith did not expect that the mice would be killed by the treatment. And as expected, the mice remained healthy.
Finally, Griffith gave mice the combined treatments from scenarios two and three. Both of these scenarios previously resulted in healthy mice, and presumably, when combined, would also lead to healthy mice. However, when Griffith infected the mice with heat-killed encapsulated S. pneumoniae along with the live nonencapsulated S. pneumoniae, the mice died. Griffith was then able to isolate living encapsulated S. pneumoniae from the dead mice.
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The introduction of new genetic material into a bacterial cell by a virus is called
transduction
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Once the vector-bacteriophage injects the donor DNA into the new host, the DNA can incorporate into the host cell’s genome and confer new properties to the cell
generalized transduction
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Because the bacteriophage takes very specific genes along with it into the new phage particles, this is called
specialized transduction
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jumping genes
transposons
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cells have what kind of genome
DNA
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viruses have what kind of genomes
RNA or DNA
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what's the first step of replication
Helicase unwinds the DNA
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what's the second step of replication
single-stranded binding proteins stabilize single-stranded DNA
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what's the third step of replication
Primase lays down one RNA primer on the leading strand and many RNA primers on the lagging strand.
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what's the fourth step of replication
DNA polymerase 3 builds DNA off RNA primers on the leading and lagging strand.
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what's the. fifth step of replication
DNA polymerase 1 replaces RNA primers with DNA
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what's the sixth step of replication
Ligase glues the lagging strands DNA (Ozaki fragments) together at junctions where RNA primers were removed.
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carries a genetic message in triplet code (codons) and is translated to build a protein
Messenger RNA
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the cloverleaf shaped molecule serves as an adaptor molecule to usher amino acids into the ribosome during translation
Transfer RNA
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takes on complex stem and loop structures and combines with proteins to build ribosomes
Ribosomal RNA
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cells have what kind of genome
DNA
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viruses have what kind of genome
DNA or RNA
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codons that encode amino acids are
sense codons
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those that encode stop signals are called
nonsense codons
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the ? encoded by the codons of mRNA directs the production of all proteins
triplet code
