Even though the S strain had been heat-killed, it changed the R strain.
Frederick Griffith was one of the leading scientists looking at the genetic role of DNA. He was working on two strains of Streptococcus pneumoniae: The rough strain (R) did not cause pneumonia, but the smooth form (S) did. When he heat-killed the S strain and gave both this and the R form to mice, the mice developed pneumonia and died. Why?
the genes of this phage were made of DNA
In an important experiment, radioactively labeled bacteriophages were allowed to infect bacteria. In the first trial, the phages contained radioactive DNA, and radioactivity was detected in the bacteria. Next, other phages containing radioactive protein were allowed to infect bacteria, and radioactivity was not detected in the bacteria. These experiments led to the conclusion that _____.
the protein and DNA of T4
Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have _____.
a nitrogenous base, a sugar, and a phosphate group
Which of the following describes a complete nucleotide?
The results of which of the following techniques were most helpful to Watson and Crick in determining the structure of DNA?
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
If you analyzed the nucleotide content of DNA, you would expect to find that _____.
hydrogen bonds between nucleotide bases
The two strands of a DNA molecule are joined to each other through _____.
Watson and Crick
Who is generally credited with discovering that the DNA molecule is constructed as a double helix?
Guanine forms three hydrogen bonds with cytosine
Which of the following accurately reflects complementary base pairing in the DNA molecule?
The strands run in opposite directions
Which of the following statements is true about double-stranded DNA?
the sequence of nucleotides along the length of one strand of the DNA molecule
The information in DNA is contained in _____.
The purines (double rings) base-pair with the pyrimidines (single rings)
Which of the following statements is true for the Watson-Crick model for DNA?
a model of DNA replication
The statement that each new molecule of DNA contains one parental and one newly synthesized strand of DNA refers to _____.
attach free nucleotides to the new strand
Cells may contain more than one kind of DNA polymerase. The role of these enzymes in DNA replication is to _____.
A polymearse constructs a new strand alongside each old one by pairing complementary nucleotides
Which description of DNA replication is correct?
an accumulation of phenylalanine and no production of tyrosine and L-Dopa
During protein metabolism, the amino acid phenylalanine is changed to the amino acid tyrosine via the enzyme phenylalanine hydroxylase (PAH). Tyrosine is then used to make L-Dopa via a second enzyme. If Beadle and Tatum's one gene-one enzyme model holds true for this metabolic pathway, what is the result of a PAH mutation that alters its functionality?
When messenger RNA (mRNA) is being transcribed, the RNA base _____ always pairs with the base _____ in DNA.
Each amino acid in a polypeptide is coded for by three bases in the DNA
Which of the following statements about the genetic code is correct?
There are six different codons that code for the amino acid leucine in a protein. Because of this, we say that the code is _____.
mRNA is synthesized on only one of the chains
During the transcription of a given portion of a DNA molecule, _____.
In order for transcription to occur in a strand of a DNA molecule, there would have to be a specific recognition sequence, called a(n) _____, upstream of the DNA sequence.
As a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred _____.
specific nucleotide sequence in DNA that signals a stop
A terminator in mRNA synthesis is a(n) _____.
Genetic information is transferred from the nucleus to the cytoplasm of eukaryotic cells in the form of _____.
transcription, RNA processing, translation
What is the proper order of the following events in the expression of a eukaryotic gene?
Exons from the same gene could be spliced in different ways to make different mRNAs
A cell biologist found that two different proteins with largely different structures were translated from two different mRNAs. These mRNAs, however, were transcribed from the same gene in the cell nucleus. Which mechanism below could best account for this?
both introns and exons are transcribed, but the RNA transcribed from introns does not leave the nucleus
Usually, in eukaryotic genes _____.
Introns are cut out, and the resilting exons are spliced together
Which of the following statements correctly describes mRNA processing in eukaryotes?
occurs in an intron
A base-substitution mutation in a germ cell line is likely to have no effect on phenotype if the substitution _____.
deliver amino acids to their proper site during protein synthesis
The function of tRNA during protein synthesis is to _____.
The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a tRNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon?
polypeptides are synthesized at ribosomes, according to instructions carried by mRNA
During translation in a eukaryotic cell, _____.
holds the growing polypeptide chain
Shown below is a ribosome in the process of translation. The P site of a ribosome _____.
The polypeptide chain moves over the bonds to the single amino acid
As shown below, during polypeptide synthesis a ribosome holds two transfer RNAs in its binding sites. One tRNA has a polypeptide chain attached to it; the other tRNA has a single amino acid attached to it. What happens next?
The figure below shows the initiation of translation. The first amino acid inserted into a new polypeptide chain in eukaryotic cells is always _____.
manufactured proteins to be short and defective
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout the organism's chromosomes. This will probably cause _____.
During the process of translation, _____ matches an mRNA codon with the proper amino acid.
Messenger RNA is made on a DNA template, and then amino-acid-bearing tRNAs line up on it through codon-anticodon pairing
Which brief outline of protein synthesis is correct?
substitution of one nucleotide
A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved _____.
one of the proteins might contain an incorrect amino acid
Imagine a DNA replication error that results in the replacement of a "T" in one of the genes with a "G" instead. What effect would this have on the cell?
only nucleic acid
When a bacteriophage infects an E. coli cell, what part of the phage enters the bacterial cytoplasm?
viral genetic material that has been incorprated into a bacterial cell's chromosome
A prophage is a(n) _____.
the nucleic acid of the phage is all that enters the host cell
In the lytic life cycle of phages, _____.
The virus gets an envelope that contains host molecules when it leaves the host cell
A microbiologist analyzed chemicals obtained from an enveloped RNA virus—similar to a mumps virus—that infects monkeys. He found that the viral envelope contained a protein characteristic of monkey cells. Which of the following is the most likely explanation?
Which of these is classified as an emerging virus that can have a direct impact on human health?
They contain the enzyme reverse transcriptase
How do retroviruses such as HIV differ from other viruses?
RNA information is copied into DNA
Reverse transcription, carried out by retroviruses, is the process by which _____.
small circular RNA...potatoes and other vegetables
Viroids are _____ molecules and are found in _____.
Diseases such as diphtheria result from a process called lysogenic conversion in which viral DNA is integrated into a bacterial chromosome, which allows particular toxins to be expressed. What mechanism of gene transfer is involved?