CH 13 bio 103

How is the four-letter language of nucleic acids converted into the 20-word language of amino acids

The four nucleic acid bases combine in three-letter sequences that define different amino acids

Refer to the accompanying figure. The component labeled as B is

RNA polymerase.

How does the first nucleotide at the 5′ end of a new mRNA chain differ from the other nucleotides in the chain?

The first nucleotide retains its triphosphate group, while the others do not.

The 3′ end of eukaryotic pre-mRNAs is changed by:

adding 100−250 adenine nucleotides

During protein synthesis, ribosomes

attach to the mRNA molecule and travel along its length to produce a polypeptide

A "5′ cap":

protects mRNA from degradation

In the accompanying figure, the portion of the molecule containing the anticodon is indicated by the label

3

Which of the following is a characteristic of uracil?

It has the ability to bond with adenine.

Initiation of transcription requires

a promoter sequence

Leader sequences contain signals that

allow the ribosomes to be properly positioned for translation of mRNA molecules

Which of the following is made from DNA?

mRNA, tRNA, and rRNA

The total number of different three-base combinations of the four nucleic acid bases is

64

The process illustrated in the accompanying figure is:

transcription

One of the mRNA codons specifying the amino acid leucine is 5′-CUA-3′. Its corresponding anticodon is:

3′-GAU-5′

Why is only one strand of DNA transcribed into mRNA?

Because transcribing both DNA strands would produce different amino acid sequences

Refer to the accompanying figure. Which label indicates the location of the promoter region?

E

Uracil forms a complementary pair with ____ in RNA and ____ in DNA.

adenine; adenine

Ribose differs from deoxyribose by having:

an extra hydroxyl group

The wobble hypothesis states that:

certain tRNA anticodons can pair with more than one codon sequence

RNA is ____ and contains the nitrogenous base ____, which is absent in DNA.

single stranded; uracil

The molecule that connects a growing polypeptide chain and mRNA is called

tRNA

Refer to the accompanying figure. The portion of the molecule labeled as 5 is:

the attached amino acid.

Linus Pauling demonstrated that

the structure of hemoglobin was altered by a mutation of a single gene

RNA synthesis is also known as:

transcription.

If an mRNA transcript of the human XYZ gene was introduced into a yeast cell, the transcript would be

translated into the human XYZ protein.