Question 1

Homologous chromosomes .&#10;A)are the same length&#10;B)have the same genes at the same loci&#10;C)pair up during cell division&#10;D)are all of the above.

Accepted Answer

Homologous chromosomes are the same length, have the same genes at the same loci, and pair up during cell division. Therefore, all of the above options are correct.

Question 2

Alu elements represent of the human genome.&#10;A)less than 1%&#10;B)4-5%&#10;C)6-8%&#10;D)more than 10%

Accepted Answer

Alu elements are short, repetitive DNA sequences that make up approximately 6-8% of the human genome.

Question 3

The most common form of DNA is A-DNA.

Accepted Answer

The most common form of DNA is actually B-DNA, which is the standard double-stranded helix structure. A-DNA is a less common form of DNA that is typically found in certain conditions, such as in RNA-DNA hybrids or in certain types of bacterial DNA.

Question 4

Type II topoisomerases .&#10;A)break both strands of DNA&#10;B)include DNA gyrase,for example&#10;C)change the linking number in steps of two&#10;D)are all of the above

Accepted Answer

Type II topoisomerases break both strands of DNA, include DNA gyrase among their examples, and change the linking number in steps of two, making all of the provided options correct descriptions of their function and characteristics.

Question 5

Topoisomerases .&#10;A)are antibiotics that kill bacterial cells&#10;B)bend DNA&#10;C)change the level of supercoiling in DNA&#10;D)repair DNA

Accepted Answer

Topoisomerases are enzymes that change the level of supercoiling in DNA. They can either relax supercoiling (type I topoisomerases) or introduce negative supercoiling (type II topoisomerases). They are not antibiotics and do not directly kill bacterial cells, nor do they bend or repair DNA.

Question 6

All of the following describe Z-DNA except .&#10;A)left-handed helix&#10;B)12 base pairs per turn&#10;C)acid conditions&#10;D)GC- or GT-rich tracts

Accepted Answer

Z-DNA is a left-handed helix with 12 base pairs per turn and is typically characterized by GC- or GT-rich tracts. However, its formation is favored under alkaline conditions, not acidic conditions.

Question 7

The melting temperature of DNA is the temperature at which .&#10;A)half of the two strands are separated.&#10;B)the two DNA strands are completely separated.&#10;C)the DNA is completely degraded.&#10;D)half of the DNA is degraded.

Accepted Answer

The melting temperature of DNA is defined as the temperature at which half of the DNA molecules are in the double-stranded state and half are in the single-stranded state, indicating the point at which 50% of the double helix has dissociated into single strands.

Question 8

The form of DNA that consists of a triple helix promoted by acid conditions and runs of purine bases is called .&#10;A)H-DNA&#10;B)Z-DNA&#10;C)A-DNA&#10;D)B-DNA

Accepted Answer

The form of DNA that consists of a triple helix promoted by acid conditions and runs of purine bases is called H-DNA. B-DNA is the most common form of DNA, characterized by a right-handed double helix. Z-DNA is a left-handed double helix form that is promoted by high salt concentrations. A-DNA is a right-handed double helix similar to B-DNA, but with a shorter and wider structure.

Question 9

Which of the following sequences would have the highest melting temperature relative to the others listed?&#10;A)5'-ATATATAT-3'&#10;B)5'-GAGAGAGA-3'&#10;C)5'-GCGCGCGC-3'&#10;D)5'-AAAAAAAA-3'

Accepted Answer

The sequence with the highest melting temperature is the one that forms the most stable double-stranded DNA. This stability depends on the base pairing between complementary nucleotides, with GC base pairs forming three hydrogen bonds, whereas AT base pairs form only two. As a result, the sequence with the highest GC content should have the highest melting temperature. Choice C has all GC base pairs, whereas the other sequences have mostly AT base pairs with few GC base pairs. Therefore, 5'-GCGCGCGC-3' would have the highest melting temperature relative to others listed.

Question 10

DNA wrapped around histones are called .&#10;A)chromatids&#10;B)nucleosomes&#10;C)heterochromatin&#10;D)300 nm fibers

Accepted Answer

DNA wrapped around histones are called nucleosomes.

Question 11

Compared to the other answers listed,which is the least compacted structure?&#10;A)DNA double helix&#10;B)chromatid&#10;C)30 nm fiber&#10;D)nucleosome

Accepted Answer

The answer of Compared to the other answers listed,which is...

Question 12

A large amount of satellite DNA is found .&#10;A)in euchromatin&#10;B)around the centromeres of chromosomes&#10;C)in loosely packed forms of chromatin&#10;D)in Alu elements.

Accepted Answer

The answer of A large amount of satellite DNA is...

Deck 4: Genes, genomes, and DNA