Chapter 17 Mastering Biology

The direction of synthesis of an RNA transcript is _____.

5' to 3'

What is a codon?

A codon is a group of three bases that can specify only one amino acid.

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.

What is true of mutations?

An addition mutation results in an added base in the DNA sequence, a deletion mutation results in the loss of a base in the DNA sequence, and addition and deletion mutations disrupt the primary structure of proteins.

Which component is not directly involved in translation?

DNA

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?

Deletion

Which of the following processes correctly describes alternative RNA splicing?

It can allow the production of proteins of different sizes and functions from a single mRNA.

What is true of a codon?

It extends from one end of a tRNA molecule.

Which of the following statements correctly describes a ribozyme?

It is an RNA with catalytic activity.

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

In bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. Which of the following statements explains this fact?

The rules for base pairing between the third base of a codon and tRNA are flexible.

What is a ribozyme?

a biological catalyst made of RNA

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

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

During RNA processing a(n) _____ is added to the 3' end of the RNA.

a long string of adenine nucleotides

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation?

a polypeptide missing an amino acid

Post-translational modifications of proteins may include which of the following processes?

addition of carbohydrates to form a glycoprotein

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon.

Translation occurs in the _____.

cytoplasm

The RNA segments joined to one another by spliceosomes are _____.

exons

Which of the following molecular structures contain codons?

mRNA

During RNA processing a(n) _____ is added to the 5' end of the RNA.

modified guanine nucleotide

Spliceosomes are composed of _____.

snRNPs and other proteins

Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what process occurs next?

translocation

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