mastering bio protein synthesis
The nitrogenous base adenine is found in all members of which group?
ATP, RNA, and DNA
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?
Any mutation in the sequence is selected against.
Which of the following provides some evidence that RNA probably evolved before DNA?
DNA polymerase uses primer, usually made of RNA.
Which of the following mutations would likely be most dangerous to a cell?
Deletion of one nucleotide
Which one of the following is true of tRNAs?
Each tRNA binds a particular amino acid.
Which of the following is a function of a poly-A signal sequence?
It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage 10-35 nucleotides away.
What is the effect of a nonsense mutation in a gene?
It introduces a premature stop codon into the mRNA.
Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell?
One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.
During splicing, which molecular component of the spliceosome catalyzes the excision reaction?
RNA
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?
RNA polymerase II
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
a base-pair deletion
What is a ribozyme?
a biological catalyst made of RNA
What does a mutagen cause?
a change in the sequence of DNA
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
a polypeptide missing an amino acid.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
A frameshift mutation could result from
either an insertion or a deletion of a base.
The flow of information in a cell proceeds in what sequence?
from DNA to RNA to protein
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
introns ... exons
The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following?
polypeptide factors plus GTP
Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is
3' UCA 5'.
RNA polymerase moves in which direction along the DNA?
3' to 5' along the template strand
The template strand of a gene contains this sequence: 3'-TAC TAG GCT AGT TGA-5'. A mutation occurs that changes the gene sequence to 3'-TAC TAG ACT AGT TGA-5'. How does this mutation affect the resulting amino acid sequence? one with the big chart)
The mutation introduces a stop codon.
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
UUU.
Alternative RNA splicing
can allow the production of proteins of different sizes and functions from a single mRNA.
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which components of the previous molecule will also be found in mRNA in the cytosol?
5' UTR E1 E2 E3 E4 UTR 3'
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A gene from an organism can theoretically be expressed by any other organism.
Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?
A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
How is translation initiated?
All of the above.
Which of the following best describes the significance of the TATA box in eukaryotic promoters?
It is the recognition site for a specific transcription factor.
Why might a point mutation in DNA make a difference in the level of a protein's activity?
It might substitute a different amino acid in the active site.
Where does RNA polymerase begin transcribing a gene into mRNA?
It starts after a certain nucleotide sequence called a promoter.
What is the function of RNA polymerase?
It unwinds the double helix and adds nucleotides to a growing strand of RNA.
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?
an assembled ribosome with a polypeptide attached to the tRNA in the P site
A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
several transcription factors
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
three ... amino acid
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to elements of this structure, where can it attach?
to the end of an intron
