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51 Cards in this Set

  • Front
  • Back
How many H bonds exist between adenine and thymine?
Two hydrogen bonds
How many H bonds exist between guanine and cytosine?
Three hydrogen bonds
In the body, nucleotides are attached to how many phosphates?
3 phosphates; triphosphate nucleotides
A phosphate is located at which end of a nucleotide?
5' end
A hydroxyl group is located at which end of a nucleotide?
3' end
Origins of replication tend to be rich in what nucleotide bases and why?
adenine and thymine rich, because the two hydrogen bonds between the pairs are weaker than the three between G-C
DNA polymerase requires what group to extend nucleotides?
A free hydroxyl group
DNA polymerase obtains the force required to make ester bonds between nucleotides from what?
The unstable, triphosphate tail on the 5' end of a nucleotide
Transcription is inhibited when chromatin is in what conformation?
Condensed chromatin
What is the function of histones?
To compact and organize DNA
What is a centrosome and when does it replicate?
A centrosome is an organelle that serves as the main Microtubule Organizing Center (MTOC). It is used to align at the equator (metaphase) and separate sister chromatids during mitosis. It replicates during interphase.
What is a sister chromatid?
A chromosome connected by a centromere to another identical chromosome.
How many sister chromatids are in a mitotic chromosome?
Two sister chromatids=One mitotic chromosome
In humans, after DNA replication, how many sister chromatids are in a cell? mitotic chromosomes? DNA strands?
92.
46.
184
What is the difference between a pair of sister chromatids and a pair of homologous chromosomes?
Sister chromatids have identical genes and alleles. Homologous chromosomes have identical genes but two copies of alleles.
DNA-dependent RNA primase provides a primer made of....
RNA
How many primers will a leading strand contain? lagging strand?
1
many
In what phase does DNA replication occur?
S phase of interphase
What is the function of ligase?
Joining of DNA fragments
Why must DNA have repair mechanisms while RNA does not?
Errors in DNA replication causes all future copies of DNA to be incorrect while a single RNA will cause a single instance of futility.
Transcription is carried out by which enzyme?
DNA dependent RNA polymerase II
What are two differences between RNA and DNA
Ribose sugar rather than deoxyribose sugar. Uracil nucleotide instead of thymine nucleotide.
Where does RNA polymerase bind?
On the promoter sequence of a gene, upstream from where transcription occurs.
What is the name of the DNA sequence found in the promoter region of a gene?
TATA box
Enhancers influence the transcription of genes but are distal to the actual site of transcription. How is this possible?
Through protein folding
Which end of mRNA is capped before leaving the nucleus?
5' end
What happens to mRNA right before it is released from RNA polymerase II?
The 3' end is polyadenylated.
What is the typical sequence that signals the termination of transcription?
AATAAA
What is the actual coding sequence of mRNA called?
Exon
What is RNA splicing?
The removal of introns and the joining of exons?
What is protein synthesis called?
Translation
How many nucleotides are in a codon?
Three
What is the size of a ribosome? How many subunits does it contain? What are the sizes of each subunit?
80 S
2
60 S and 40 S
Are the sequences of tRNAs found in eukaryotes different than those in prokaryotes?
No, they are identical.
What is the name of the reaction whereby a tRNA molecule is joined to its specific amino acid and what enzyme catalyzes this reaction?
Charging
aminoacyl tRNA synthetase
How does the enzyme link tRNA to its specific amino acid?
aminoacyl tRNA synthetase covalently links the correct amino acid to the 3' end of the tRNA using the energy of ATP
How many aminoacyl tRNA synthetases exist?
At least one for each of the 21 amino acids
How many steps are involved in translation and what are they called?
3: initiation, elongation, and termination
What is the first step of initiation?
Binding of the small ribosomal subunit/Met-charged tRNA complex to the 5' cap of the mRNA
What happens after the small ribosomal unit binds to the mRNA?
It moves in the 3' direction until it finds the start codon AUG (for methionine). Met-charged tRNA then associates with the start codon causing the association of the large 60S ribosomal unit to form the complete 80S ribosome.
What is the sequence of mRNA that serves as the start codon for translation? What amino acid does it code for?
AUG; Methionine
What are the names of the binding sites of the ribosome?
Peptidyl (P site) and Aminoacyl (A site)
Where is the initiator tRNA at the start of elongation?
P site
When the next charged tRNA "enters" the ribosome, which site will it occupy?
A site
What is the enzymes that catalyzes the formation of a bond between amino acids in the ribosome? What kind of bond does it form?
peptidyl transferase; peptide bond
What happens to the tRNA in the in P site after the ribosome shifts over one codon?
The uncharged tRNA is ejected from the ribosomal complex, leaving its amino acid covalently (peptide) bonded to the charged tRNA that now occupies the P site.
What happens when a termination codon enters the A site?
Since there is no tRNA with a complementary anticodon to a stop codon, a release factor recognizes and binds the termination codon. This causes the translation complex to fall apart and cleave the polypeptide from the final tRNA.
Why are there 64 codons for 20 amino acids?
Amino acids can be encoded by more than one codon.
What happens to damaged, misfolded, or short life-time proteins?
They are bound by ubiquitin and then degraded into amino acids by a proteosome.
How do newly synthesized proteins reach the endoplasmic reticulum so they can be translocated to the Golgi apparatus?
A ribosome translates a specific signal sequence on the protein that is recognized by a signal recognition particle. This causes the ribosome to associate with the endoplasmic reticulum, where the ribosome continues to translate newly formed protein into the lumen of the ER.
How are newly synthesized plasma membrane proteins incorporated into the cellular membrane?
After being endocytosed into the Gogli, the protein is processed and then embedded in plasma membrane of the Gogli. The membrane bound with proteins is then exocytosed and travels to the cellular membrane where it fuses.