The flow of information in a cell proceeds in what sequence?
from DNA to RNA to protein
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
three ... amino acid
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.
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
What is a ribozyme?
a biological catalyst made of RNA
Which one of the following is true of tRNAs?
Each tRNA binds a particular amino acid.
How is translation initiated?
The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation.
What does a mutagen cause?
a change in the sequence of DNA
Which of these is currently considered the best definition of a gene?
A gene codes for either a polypeptide or an RNA molecule.
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.
The nitrogenous base adenine is found in all members of which group?
ATP, RNA, and DNA
Alternative RNA splicing
can allow the production of proteins of different sizes from a single mRNA.
Which of the following is a function of a signal peptide?
to translocate polypeptides across the ER membrane
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.
What is the effect of a nonsense mutation in a gene?
It introduces a premature stop codon into the mRNA.
Of the following, which is the most current description of a gene?
a DNA sequence that is expressed to form a functional product: either RNA or polypeptide