Lecture 16 Study Questions

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

40%

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' AAGGCTT 3'

5' AAGCCTT 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' GCGAATA 3'

5' TATTCGC 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' TTCCGGA 3'

5' TCCGGAA 3' paired then written backwards

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature?

A with T

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature?

C with G

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

DNA ligase

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

Why are primases necessary in order for DNA replication to occur?

DNA polymerases can not initiate synthesis of new nucleotide chains

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain

The process by which DNA molecules are copied so that when cells divide each cell can have a complete copy of the DNA is known as

DNA replication

Will the chromosomes you pass onto your children be shorter than your chromosomes?

Hopefully not, because telomerase will restore the telomeres in your germline cells (the cells that produce egg or sperm cells) to approximately their original length.

What kind of chemical bond is found between paired bases of the DNA double helix?

Hydrogen

Which of the following statements describes the eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

Why are there concerns about using increased telomerase activity to slow down the aging process?

One concern is that increasing telomerase activity could increase cancer rates.

Which of the following statements regarding DNA polymerases is TRUE?

all of these statements are true

The formation of hydrogen bonds between complementary nucleotides is known as

base pairing

The reaction used to join together nucleotides to form a nucleotide chain is known as a

dehydration reaction

In a nucleosome, the DNA is wrapped around

histones.

In a double-stranded DNA molecule, the two DNA strands base pair in such a way that the 5' end of one DNA strand base pairs with the 3' end of the other DNA strand. The two DNA strands are said to be

in an antiparallel arrangement

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

leading strands and Okazaki fragments.

Which of the following represents the order of increasingly higher levels of organization of chromatin?

nucleosome, 30-nm chromatin fiber, looped domain

DNA polymerases can add deoxyribonucleotides to

only the 3' end of an existing nucleotide chain

Histones are

part of nucleosomes

Which of the following describes the sequence of events that occurs during DNA replication of a double-stranded DNA molecule?

separation of the DNA strands at DNA replication origins, unwinding of the DNA double helix, synthesis of RNA primers, synthesis of DNA, ligation of DNA fragments

The ends of linear chromosomes are known as

telomeres

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

How do the nucleotides used to make RNA molecules differ from those used to make DNA molecules?

the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of thymine as one of their nitrogenous bases