Bio Unit 3 Ch 17

What is the function of RNA polymerase?

It unwinds the double helix and adds nucleotides to a growing strand of RNA.

A particular triplet of bases in the template strand of DNA is 5-AGT-3. What would be the corresponding codon for the mRNA that is transcribed?

3-UCA-5

Mutagen

A chemical or physical agent that interacts with DNA and causes a mutation.

Ribosomes

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus.

polyribosomes

A group of several ribosomes attached to, and translating, the same messenger RNA molecule.

Insertion

A mutation involving the addition of one or more nucleotide pairs to a gene.

nonsense mutations

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

Introns

A noncoding, intervening sequence within a eukaryotic gene.

signal-recognition particle

A protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome.

transcription unit

A region of DNA that is transcribed into an RNA molecule.

transcription factors

A regulatory protein that binds to DNA and affects transcription of specific genes.

Exons

A sequence within a primary transcript that remains in the RNA after RNA processing; also refers to the region of DNA from which this sequence was transcribed.

Promoter

A specific nucleotide sequence in the DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.

Codons

A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

Messenger RNA

A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.

RNA polymerase

An enzyme that links ribonucleotides into a growing RNA chain during transcription, based on complementary binding to nucleotides on a DNA template strand.

primary transcript

An initial RNA transcript from any gene; also called pre-mRNA when transcribed from a protein-coding gene.

terminator

In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA.

RNA processing

Modification of RNA primary transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends.

Translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of language from nucleotides to amino acids.

A particular triplet of bases in the coding strand of DNA is AAA. The anticodon on the tRNA that binds this mRNA codon is _____.

UUU

point mutation

a change in a single nucleotide pair of a gene

Mutation

a change in the nucleotide sequence of an organisms DNA or in the DNA or RNA of a virus

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

frameshift mutation

a mutation occuring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons

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

The flow of information in a cell proceeds in what sequence?

from DNA to RNA to protein

Ribosomal RNA

RNA molecules that, together with proteins, make up ribosomes; the most abundant type of RNA

In eukaryotes, there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

RNA polymerase II

transcription initiation complex

The completed assembly of transcription factors and RNA polymerase bound to a promoter.

Which one of the following is true of tRNAs?

tRNAs carry special sequences known as codons. Each tRNA binds a particular codon. There are four types of tRNA. tRNAs are double-stranded. None of the listed answers is correct.

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

Which of the following processes is the first event to take place in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA

Transcription

the synthesis of RNA using a DNA template

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.

three ... amino acid

RNA splicing

After synthesis of a eukaryotic primary RNA transcript, the removal of portions of the transcript (introns) that will not be included in the mRNA and the joining together of the remaining portions (exons).

Transfer RNA

An RNA molecule that functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA.

gene expression

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs.

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

Which of the following statements is the most current description of a gene?

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

Which of the following DNA mutations is most likely to damage the protein it specifies?

a base-pair deletion

What is a ribozyme?

a biological catalyst made of RNA