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Student questions - replication, transcription, tr


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What is RNA splicing?
Editing of the pre-mRNA transcript in which introns are removed and exons are joined together.
In which direction is RNA made during transcription?
5' end to 3' end
What is the purpose of the protein DNA ligase in DNA replication?
DNA ligase joins the phosphodiester bonds in the DNA backbone and in this way it joins the Okazaki fragments on the lagging strand. It also has an important role in DNA repair, during completion of short patch DNA synthesis.
Where in the cell is DNA located?
In Eukaryotes it is located in the nucleus (which is separated by membranes from the cytoplasm), whereas in prokaryotes it is in the cytoplasm, and it is not separated by membranes.
What is the name of the protein which divides the two strings of DNA?
Helicase
How many different amino acids are encoded by the genetic code?
20
What is responsible for the first level of DNA packing into chromatine?
Histones
What is the name of the enzyme which cuts out the pieces of faulty DNA
DN-ase which is a nuclease.
What is the distance between two consecutive base pairs in the DNA?
0.34nm
Describe the process known as gene expression - describe the steps in prokaryotes!
1. DNA is transcribed to mRNA in cytoplasm; 2. mRNA is translated to proteins in the cytoplasm of the prokaryotic cell
Describe the process known as gene expression - describe the steps in eukaryotes!
1. DNA is transcribed to pre-mRNA in nucleus; 2. pre-mRNA is modified and spliced to mRNA; 3. mRNA is exported accross the nuclear membrane; 4. mRNA is trasnlated to protein.
Which process can produce two or more different polypeptides from the same pre-mRNA sequence?
Alternative splicing
What is the name of the cut-and-paste process where parts of the pre-mRNA are removed and the remaining fragments are ligated together?
Splicing
What is a transcription unit?
The stretch of DNA downstream from the promoter which usually contains an RNA-coding sequence and a terminator.
What are the fragments formed on the lagging strand called during DNA replication?
Okazaki fragments
Which bases are the purines and which are the pyrimidine?
Purines are adenine and guanine; pyrimidines are thymine and cytosine.
What are the two types of Nucleic Acids called?
Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA)
Which nucleotides can be found in RNA?
Adenine, guanine, cytosine, uracil
What is the transcribing enzyme called?
RNA polymerase
What is the start codon?
AUG which encodes for the aminoacid methionine
What do you call a group of large organic molecules consisting of one or more amino acid chains?
Protein
In which direction is a DNA strand transcribed?
5' to 3 '
In which direction is a DNA strand replicated continuously?
5' to 3'
What is the name of the nucleotide sequence, which works as a binding site for trasncription factors in eukaryotes?
TATA box
What polypeptide product would you expect from a poly-G mRNA that is 30 nucleotides long?
10 glycine amino acids.
What kind of reaction happens when the phosphate in ATP reacts with water?
Exergonic reaction.
Which is more reactive - Thymine or Uracil? Why?
Uracil is more reactive, thymine has an aditional methyl group which stabilizes it, making it less reactive.
What is a promotor?
A promotor is the region where transcription starts.
What binds to the promotor in prokaryotes?
The sigma factor and the RNA polymerase itself, which will initiate transcription.
what binds to the promotor in eukaryotes?
Several transcription factors, which have a role in preparing the site for RNA-polymerase attachement.
Why is genetic information stored in DNA, and not RNA?
DNA is more stable and better at self repair. RNA is reactive because of its -OH group on the ribose which invites hydrolysis reactions, and it's less stable uracil.
What are the noncoding segments of nucleic acid that lie between coding regions during RNA splicing called?
Introns
How many tRNAs can bind to a ribosome at once?
One
What are the sites on the ribosome established during translation?
A) the aminoacyl site; E) the exit site; P) the peptidyl site.