Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
41 Cards in this Set
- Front
- Back
|
define: codon
|
Codon is the term used to define three groups of ribonucleotides found in mRNA molecule
|
|
|
What does it mean when u say that the genetic code is unambiguous?
|
It means that each codon can only specify one single amino acid.
|
|
|
What does it mean when you say that the genetic code is degenerate?
|
It means that a given amino acid can be specified by more than one codon.
|
|
|
define: frameshift mutation
|
the insertion or deletion of a series of nucleotides that is not divisible by three and thus shifting the frame of reading of the codons
|
|
|
define: transcription
|
The process by which RNA molecules is synthesized on a DNA template
|
|
|
Enumerate some observations that led to the idea that RNA is involved as an intermediate molecule in the process of information flow between DNA and protein.
|
1. DNA is located within the nucleus. However, protein synthesis occurs outside the nucleus in the cytoplasm. Therefore, DNA does not seem to have any direct participation in protein synthesis
2. RNA is synthesized in the nucleus and is closely related to DNA 3. RNA migrates to the cytoplasm, where protein synthesis occurs. 4. The amount of RNA is generally proportional to the amount of protein in the cell. |
|
|
What is the function of RNA polymerase?
|
Direct RNA synthesis using a DNA template.
|
|
|
What is a holoenzyme?
|
Holoenzyme is the active form of RNA polymerase
|
|
|
Which subunits of RNA polymerase provide the catalytic basis and active site for ?
|
B and B' subunits (B as in Beta)
|
|
|
Which subunit of RNA polymerase plays a regulatory function involving the initiation of RNA transcription?
|
sigma subunit.
|
|
|
Whats the end result of the DNA transcription process?
|
Transcription results in the production of a single-stranded RNA molecule complementary to a region along one of the two strands of the DNA double helix.
|
|
|
Define: Antisense DNA strand (template strand)
|
The antisense strand is the strand of DNA transcribed into mRNA during transcription.
|
|
|
Define: Sense DNA strand (nontemplate strand)
|
The DNA strand in a gene that has the same sequence as the primary transcript (the RNA production of transcription)
|
|
|
The initial step of transcription is referred to as template binding. When is the site of this initial binding established?
|
When the sigma subunit of RNA polymerase recognizes the promoters. The enzyme is believed to explore the length of DNA until it recognizes the promoter region abd binds to about 60 nucleotide pairs of the helix.
|
|
|
Define: promoters
|
specific sequence of DNA
|
|
|
Where is the promoter region located along the DNA?
|
5' (upstream) region
|
|
|
When does transcription actually begins? (also called transcription start site)
|
After the RNA polymerase recognizes the promoter region of the antisense DNA strand, it binds to about 60 nucleotide pairs of the DNA. Once this occurs, the helix is denatured and this allows the antisense strand to be exposed to the actions of RNA polymerase.
|
|
|
Define: consensus sequences of DNA
|
These are sequences that share homology in different genes of the same organism, or in one or more genes of a closely related organism.
|
|
|
What is a TATA box?
|
A eukaryotic consensus sequence comparable to that in the prokaryotic -10 region.
|
|
|
The efficiency of initiation of transcription depends on the form of _____ that RNA polymerase has.
|
Sigma form. The most general form is sigma 70.
|
|
|
How might an “antisense” drug
work? |
Antisense drugs work by preventing improperly assembled protein trains from ever leaving the cellular station. To produce a protein, the cell first makes a messenger RNA (mRNA) copy of the gene containing the necessary information. "This message is then read by the cell and translated into the process to produce the protein," explains Crooke.
Protein production is a complex, two-step process. The first step, called transcription, occurs in the nucleus. This is the part of the cell that holds the DNA, or genetic recipe for life. The recipe for a particular protein is copied from a section of DNA–a gene–into mRNA. The mRNA then leaves the nucleus. The second step, called translation, occurs in the surrounding area, outside the nucleus but inside the membrane that forms the cell wall. Amino acids floating in this viscous sea of cytoplasm couple to each other, in the precise order specified by the mRNA. The finished product: a new protein that can become part of a muscle, eyeball or toenail. Antisense technology uses synthetic DNA or RNA–called oligonucleotides–to block the production of faulty proteins. "An antisense drug specifically binds to the mRNA coding for a target protein to prevent the cell from using that mRNA to make the target [disease-associated] protein," says Crooke. These custom-designed compounds are called antisense drugs because their molecular structure is the opposite of the "sense" or pattern of the original mRNA. |
|
|
What is a termination factor, rho (p) ?
|
Rho is a large hexameric protein that physically interacts with the growing RNA transcript, facilitating termination of transcription.
|
|
|
How is eukaryotic transcription different from prokaryotic transcription?
|
1. Transcription in eukaryotes occurs within the nucleus under the direction of three separate RNA polymerase. Unlike prokaryotes, in Eukaryotes, the RNA trascript (product of transcription) is not free to associate with ribosomes prior to completion of transcription. For the mRNA to be translated, it must move out of the nucleus into the cytoplasm.
2. Initiation of transcription of eukaryotic genes requires that the compact chromatin fiber must be uncoiled and the DNA made accesible to RNA polymerase and other regulatory proteins. 3. Initiation and regulation of transcription involve a more extensive interaction between cis-acting upstream DNA sequences and trans-acting protein factors. Enhancers may be also located in the 5' regulatory region upstream from the initiation point upstream. |
|
|
What is the function of enhancers?
|
increases the transcriptional activity of nearby genes
|
|
|
Define: pre-mRNA
|
The "crude" mRNA product of transcription. After transcription pre-mRNAs are extensively modified first before they are translated. Only found in the nucleus. Part of hnRPS
|
|
|
define: hnRNA (heterogeneous nuclear RNA)
|
a group of molecules found only in the nucleus. pre-mRNA belongs to this group.
|
|
|
Which eukaryotic RNA polymerase produces rRNA and is located in the nucleolus?
Which one produces mRNA, snRNA and is located in the nucleoplasm? Which one produces 5S rRNA, tRNA and is located in the nucleoplasm? |
1. RNA Poly I
2. RNA Poly II 3. RNA Poly III |
|
|
Which RNA Poly is responsible for the production of all mRNAs in eukaryotes?
|
RNA Poly II
|
|
|
Define: core-promoter element
|
A DNA sequence that determines where RNP II binds to the DNA and where it begins copying DNA into RNA.
|
|
|
What does the term promoter refer to in eukaryotes?
|
It refers to the core-promoter elements, enhancers, and promoter.
|
|
|
The cis-acting core promoter ____ _____ is the site where RNP II binds to the DNA template, and transcription typically begins 25-30 bp downstream from it.
|
TATA box
|
|
|
The ____ ____ is a cis-acting eukaryotic promoter that enhances the efficiency of the promoter.
|
CAAT box
|
|
|
____ are often found further upstream from the transcription start site. Part of eukaryotic promoters that is essential to highly efficient initiation of transcription
|
Enhancers
|
|
|
What happens when a mutation occur within an RNA sequence causing it to not be able to add the poly-A tail?
|
In the absence of this tail, RNA transcript is rapidly degraded.
|
|
|
Define: intron
|
DNA sequences that are not represented in the final mRNA product
|
|
|
define: exon
|
DNA sequences that are retained and expressed in the mRNA product
|
|
|
define: Split genes
|
genes that contain the -intervening sequences-, which are nucleotide sequences that are removed before the mature mRNA is translated.
|
|
|
what are ribozymes
|
RNAs that are capable of splicing themselves
|
|
|
Re-read Splicing Mechanisms
|
Page 324!
|
|
|
What does group I intron represent? How are they removed?
|
introns that are part of the primary transcript of rRNAs. They are removed by two esterification reactions with guanosine involved as a cofactor.
|
|
|
What does group II intron represent?
|
introns that part of the primary mRNA and tRNA transcripts. Guanosine not involved as a cofactor during the autocatalytic exicision.
|
