Question 1

Which of the following is guanosine?

Accepted Answer

The answer of Which of the following is guanosine?
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Question 2

Different versions of a gene are called _________.

Accepted Answer

Different versions of a gene are called alleles.

Question 3

The genome is essentially equivalent to all of the genetic information that is present in a ______ set of chromosomes.

Accepted Answer

The answer of The genome is essentially equivalent to all...

Question 4

How is the extent of DNA denaturation usually measured?

Accepted Answer

Absorbance of UV light by DNA increases as DNA denatures. This is because the double-stranded DNA absorbs UV light at a lower wavelength than single-stranded DNA. As the DNA strand denatures and separates into single strands, the absorbance of UV light increases, allowing for the extent of denaturation to be measured.

Question 5

What statement below explains the uniform width of the DNA molecule along its entire width?

Accepted Answer

The answer of What statement below explains the uniform width...

Question 6

What function does topoisomerase II serve during mitosis?

Accepted Answer

Topoisomerase II is essential in helping to resolve the interlocking coils of DNA in replicated chromosomes to allow for separation of daughter chromosomes during mitosis. This is required for successful cell division.

Question 7

The variety and number of DNA sequence copies in the genome are known as genome _______.

Accepted Answer

Genome complexity refers to the variety and number of DNA sequence copies in the genome.

Question 8

You isolate DNA from a particular organism and analyze it.The amount of adenine was 6 µmoles and the A+T/G+C ratio is 4.0.How much guanine should be in the sample?

Accepted Answer

Given the A+T/G+C ratio is 4.0 and the amount of adenine (A) is 6 µmoles, the total amount of adenine and thymine (A+T) is 4 times the amount of guanine and cytosine (G+C). Since A = T in DNA, A+T = 12 µmoles. Therefore, G+C must be 3 µmoles (since 12 µmoles is 4 times 3 µmoles). Given that G = C in DNA, the amount of guanine (G) must be half of 3 µmoles, which is 1.5 µmoles.

Question 9

Why are satellite DNAs separated from the bulk of the genome during density gradient centrifugation?

Accepted Answer

Satellite DNAs have a significantly different base composition compared to the bulk of the genome, which allows them to be separated during density gradient centrifugation. The differences in base composition can affect the buoyancy of the DNA fragments, allowing for differential migration in the gradient.

Question 10

The information encoded in DNA resides in ________.

Accepted Answer

The DNA base sequence contains the genetic information encoded in DNA. It determines the sequence of amino acids in proteins, which govern all cellular functions. The phosphates and sugars in the backbone of DNA serve mainly to support the base sequence and provide stability to the molecule.

Question 11

Which type of DNA sequence is typified by short sequences of DNA (five to a few hundred base pairs in length)repeated a large number of times in tandem to form very large clusters,each containing up to several million base pairs of DNA?

Accepted Answer

Satellite DNAs are characterized by short, highly repetitive DNA sequences that are repeated in tandem to form large clusters. These clusters can be very large, containing up to several million base pairs of DNA. Minisatellite and microsatellite DNAs also contain repetitive sequences, but they are typically shorter in length and do not form clusters as large as satellite DNAs. Consensus sequences refer to regions of DNA that are highly conserved across different organisms or even within the same organism. Microminisatellite DNAs are not a recognized classification of DNA sequences.

Question 12

Which type of enzyme makes a transient break in both DNA duplex strands and then transports another segment of a DNA molecule (or separate molecule entirely)through the break and reseals the severed strands?

Accepted Answer

Type II topoisomerase makes a transient break in both DNA duplex strands and then transports another segment of a DNA molecule (or separate molecule entirely) through the break and reseals the severed strands. Type I topoisomerase only breaks one strand of the DNA duplex, and Type I topologicase and Type II topologicase are not enzymes that exist. Type I isomerase also does not perform this function.

Question 13

What gives a DNA molecule its negative charge?

Accepted Answer

Phosphate groups within the DNA molecule contain a negative charge due to the loss of their proton.

Question 14

The ends of a polynucleotide chain are the ____ end and the ____ end.

Accepted Answer

The 3' end of the polynucleotide chain refers to the carbon atom at the end of the sugar molecule that is attached to the hydroxyl (-OH) group. The 5' end refers to the carbon atom at the end of the sugar molecule that is attached to the phosphate group. Therefore, the ends of a polynucleotide chain are the 3' end and the 5' end.

Question 15

________ refers to the fact that the sequence of one DNA strand specifies the sequence of the other strand in the double helix.

Accepted Answer

Complementarity refers to the fact that A always pairs with T, and C always pairs with G in a nucleotide sequence. Therefore, if the sequence of one strand is known, the sequence of the complementary strand can be deduced.

Question 16

What technique supplied the data that led Watson and Crick to the double helical structure of DNA?

Accepted Answer

Watson and Crick used X-ray diffraction/crystallography data obtained by Rosalind Franklin and Maurice Wilkins to determine the double helical structure of DNA.

Question 17

Which type of enzyme is essential for processes like DNA replication and transcription to prevent excessive supercoiling from developing as the complementary strands of the DNA duplex separate and unwind?

Accepted Answer

Topoisomerase I is an enzyme that helps relieve the torsional strain that occurs during DNA replication and transcription by making single-strand breaks in the DNA, allowing it to unwind and then resealing the breaks.

Question 18

What method can be used to generate DNA fragments of a uniform size of about 1000 nucleotides?

Accepted Answer

Forcing the DNA through a tiny orifice under high pressure using a technique called sonication or nebulization can generate DNA fragments of uniform size. This method is commonly used in genome sequencing and other molecular biology techniques. Adding ribonuclease or deoxyribonuclease can cleave or degrade DNA, while changing the salt concentration would not necessarily result in uniform size fragments.

Question 19

In a right-handed double helix,if one looks down the central axis of the molecule,_________.

Accepted Answer

In a right-handed double helix, each strand follows a clockwise path as it moves away from the observer when looking down the central axis of the molecule.

Question 20

The original model of DNA structure stated that each unit of structure in DNA contained all four nitrogenous bases;it was called the ________.

Accepted Answer

The original model of DNA structure was the Tetranucleotide Theory, which proposed that each unit of structure in DNA contained all four nitrogenous bases (adenine, guanine, cytosine, and thymine) in equal amounts. This theory was later disproven by the discovery of the double helix structure, which showed that the nitrogenous bases were paired in a specific way.

Quiz 10: The Nature of the Gene and the Genome