Alvin is studying a model of the chemical structure of a common nucleic acid. He observes that the nucleic acid consists of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), and uracil (U). Alvin's observation most strongly supports which of these conclusions?

CHOOSE ONE ANSWER

• The nucleic acid is a form of RNA, and is not DNA.

• The nucleic acid is either mRNA or rRNA, but not tRNA.

• The nucleic acid is either RNA or DNA.

• The nucleic acid is DNA, and is not RNA.

There are three main types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). Which type or types of RNA contain a copy of the instructions that a gene carries?

CHOOSE ONE ANSWER

• mRNA only

• rRNA only

• mRNA and tRNA

• mRNA, rRNA, and tRNA

A molecular biologist is developing a computer model of the transcription of a gene into RNA. Which event should be included in the model before transcription occurs?

CHOOSE ONE ANSWER

• the removal of introns from the gene

• RNA polymerase inserting itself into the gene

• RNA polymerase binding to a region near the gene, called the promoter

• the joining together of exons to form the gene

Robert is studying a long list of letters. The letters represent the order of nitrogenous bases in a molecule of mRNA. The first several bases in the list are shown below. AUGCCACAGGUUCAUCCGAA... To identify the amino acid sequence encoded by the mRNA, which would be the most useful first step for Robert to follow?

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• Calculate the frequencies of each letter.

• Count the number of letters in the list.

• Separate the list into three-letter "words."

• Separate the list into two-, three- and four-letter "words."

A molecule of tRNA includes a sequence of three nitrogenous bases called an anticodon. What is the role of the anticodon in the process of translation?

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• The anticodon binds to a codon on rRNA.

• The anticodon binds to a codon on mRNA.

• The anticodon binds to a specific amino acid.

• The anticodon binds to the promoter, a region of DNA.

Translation involves several different types of tRNA molecules. Which statement best describes how tRNA molecules assemble amino acids into a polypeptide?

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• One tRNA molecule assembles the polypeptide, and the others assist it.

• Three tRNA molecules assemble the polypeptide, and the others assist them.

• Each tRNA molecules assembles a different part of the polypeptide, and all at the same time.

• The different tRNA molecules act in a specific order, one after the other like an assembly line.

A point mutation changes a codon in an mRNA molecule. Will the mutation affect the polypeptide that forms? Why?

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• Yes. Each amino acid is specified by only one codon.

• No. The structure of DNA, and not RNA, determines the polypeptide.

• Maybe. Some codons are translated into two or more amino acids.

• Maybe. Some sets of codons are translated into the same amino acid.

Tags

NGSS.HS-LS3-2

A normal polypeptide includes the following sequence of amino acids:

Iso-Leu-Pro-Val-His-Ser-Thr-Met

After a mutation, the amino acid sequence becomes the following:

Iso-Leu-Pro-Val-Tyr-Arg-Iso-Gly

Which of the following changes to a nitrogenous base in mRNA is most likely to have occurred?

CHOOSE ONE ANSWER

• A cytosine (C) was replaced with a uracil (U).

• A uracil (U) was replaced with a thymine (T).

• An adenine (A) was removed and not replaced.

• The codon ACU was removed and not replaced.

Tags

NGSS.HS-LS1-1

NGSS.HS-LS3-2

Which conclusion about the genetic code is most strongly supported by the evidence presented in the diagram?

CHOOSE ONE ANSWER

• All amino acids may be encoded by more than one codon.

• Many amino acids, although not all of them, may be encoded by more than one codon.

• Every codon may be translated into two or more amino acids.

• Many codons, although not all of them, may be translated into two or more amino acids.

A sequence of mRNA contains the following bases, which are translated as three codons. ACUACGACA Which amino acids are produced by this sequence? Select all of the amino acids that apply.

CHOOSE ONE ANSWER

• threonine only

• threonine and arginine only

• threonine, arginine, and isoleucine

• arginine, serine, and isoleucine