28 terms

Mastering Biology Ch. 17

Polypeptides are assembled from
amino acids
RNA processing converts the RNA transcription into _____.
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
The direction of synthesis of an RNA transcrpt is _____.
5' --> 3'
During RNA processing a(n) _____ is added to the 5' end of the RNA.
modified guanine nucleotide- the 5' cap consists of a modified guanine nucleotide
During RNA processing a(n) is added to the 3' end of the RNA.
a long string of adenine nucleotides- A poly-A tail is added to the 3' end of the RNA.
Spliceosomes are composed of _____.
snRNPs and other protiens
The RNA segments joined to one another by spliceosomes are _____.
Translation occurs in the _____.
cytoplasm- ribosomes, the sites of translations, are found in the cytoplasm
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.
CUG- in RNA uracil replaces thymine
the initiator attataches at the ribosome's _____ site.
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
a frameshift deletion at the beginning of the gene- it would affect every codon after the point where the mutation occurred. During protein synthesis, incorrect amino acids would be inserted from the point where the frameshift mutation occurred on; the resulting protein would most probably be nonfunctional. For this reason, a frameshift mutation at the beginning of a gene is generally the most severe type of mutation.
True of false? A codon is a group of three bases that can specify more than one amino acid.
False- a codon is a group of three bases that can specify only one amino acid
Which of the following statements about mutations is false?
A knock-out mutation results in a total absence of the mutated protein.- a knock out mutation refers to the loss of a protein's function but not necessarily to its complete absence.
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
Deletion- the original sequence has lost the base C
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
one addition and one deletion mutation.
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?
Two- the second and third codons in the new sequence are different from the original codons.
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?
An addition mutation and a deletion mutation.
A _____ mutation leads to early termination of protein synthesis
Protein synthesis ends when a stop _____ is produced
A change in any triplet of bases in the mRNA sequence may or may not affect the coding of a(n) _____ and change the structure of the synthesized protein.
amino acid
A _____ mutation results in the insertion of the same amino acid as was coded for by the original nucleotide sequence
Base substitution mutations alter a(n) _____ in the original DNA sequence.
A _____ mutation can dramatically alter protein structure because it results in the insertion of a different amino acid than was coded for by the original nucleotide sequence.
nonsense mutation
the new base changes an amino acid codon to a stop codon, ending protein synthesis and resulting in a shorter and usually nonfunctional protein
missense mutation
the new base leads to the insertion of a different amino acid than had been coded for, possibly altering the resulting protein's structure.
silent mutation
the new base does not change the amino acid sequence coded for by the original DNA strand