Deck 5: Genome Organization and Evolution

Question 1

The term genome is used interchangeably with all of the following terms except:

A) chromosomal DNA
B) nuclear DNA
C) plasmid DNA
D) genomic DNA

Answer 1

plasmid DNA

Question 2

How many base pairs of DNA are in the human genome?

A) 3 X 10⁹
B) 3 X 10⁸
C) 3 X 10⁷
D) 3 X 10⁶

Answer 2

3 X 10⁹

Question 3

Eukaryotic cells must fit approximately _____ of unpacked DNA into the spherical nucleus, which is a less than _________ diameter space.

A) 2 millimeters (mm), 10 mm
B) 2 mm, 0.010 mm
C) 2 meters (m), 10 mm
D) 2 m, 0.010 mm

Answer 3

2 m, 0.010 mm

Question 4

Which of the following properties do you predict to be most critical to histone association with DNA?

A) Histones are small proteins.
B) Histones are positively charged.
C) Histones are highly conserved.
D) There are at least five different histone proteins in every eukaryotic cell.

Question 5

The term nucleosome means

A) the core octamer of histones plus 146 base pairs of DNA.
B) the core octamer of histones plus the linker histone and approximately 180 base pairs ofDNA.
C) the core octamer of histones.
D) an octamer of histone H1 proteins.

Question 6

The core octamer is composed of

A) two tetramers of histones H3 and H4
B) one each of 8 different types of histones.
C) a tetramer of histones H3 and H4, and two dimers of histones H2A and H2B.
D) the linker histone H1

Question 7

The __________________ are the site of many post-translational modifications of the histone proteins.

A) conserved wing helix folds
B) charged tails at the N-terminal end
C) charged tails at the C-terminal end
D) extended histone-fold domain at the C-terminal end

Question 8

Brief digestion of eukaryotic chromatin with micrococcal nuclease gives a visible ladder of bands on an agarose gel separated from each other by multiples of 180-200 bp. The fragment size represents

A) DNA that was wrapped around the core histone octamer.
B) linker DNA.
C) the different histone proteins.
D) multiples of single nucleosomal repeat lengths of DNA.

Question 9

DNA wrapped around the histone core octamer appears as "beads-on-a-string" by electron microscopy. Upon the addition of salt or when observed in situ, nucleosomal arrays further compact to form:

A) a 10 nm helical solenoid.
B) a 10 nm fiber.
C) a 30 nm fiber with a zig-zag ribbon structure.
D) a 30 nm loop domain

Question 10

A eukaryotic chromosome consists of

A) a single molecule of double-stranded DNA.
B) a single molecule of single-stranded DNA.
C) multiple intertwined molecules of single-stranded DNA.
D) multiple intertwined molecules of double-stranded DNA.

Question 11

What statement is not true about plasmid DNA?

A) Plasmid DNA is extrachromosomal
B) Plasmid DNA is only found in bacteria
C) Plasmid DNA is self-replicating
D) Most plasmids are small, double-stranded circles.

Question 12

What statement is not true about bacteriophages?

A) Bacteriophages are viruses that infect bacteria.
B) Bacteriophages are viruses that infect both bacterial and mammalian cells.
C) Bacteriophages have been widely used as a tool for molecular biology research.
D) The bacteriophage genome usually consists of a single DNA molecule.

Question 13

Electron micrographs of chromatin formation in simian virus 40 (SV40) have revealed that

A) the virus uses host cell histone H1 to form nucleosomal-like particles.
B) the virus does not make use of host cell histones to package its genome.
C) the circular double-stranded viral genome is organized into several minichromosomes.
D) the circular double-stranded viral genome is organized into a single minichromosome.

Question 14

What statement is not true about chloroplasts and mitochondria?

A) They both contain their own genetic information that is inherited independently of thenuclear genome.
B) Mitochondrial and chloroplast genomes are either circular or linear.
C) They both are thought to have originated from cyanobacteria.
D) The organelles are only contributed from the maternal gamete.

Question 15

The location of the centromere within a chromosome is determined by

A) the presence of the histone variant CenH3.
B) the presence of an evolutionarily conserved centromere-determining sequence.
C) the presence of linker histone.
D) the point of equidistance between the two chromosome ends.

Question 16

You use two different fluorescently labeled antibodies to detect CenH3 and a telomere-binding protein in mouse cells. You find that the two signals are so close that they almost overlap at one of the two ends of each chromosome. From this observation, you conclude that

A) mouse chromosomes are acrocentric.
B) mouse chromosomes are metacentric.
C) mouse chromosomes have non-functional centromeres.
D) mouse chromosomes have one non-functional telomere per chromosome.

Question 17

Which of the following statements about sex chromosomes is not true?

A) All sexually reproducing animal species specify gender by sex chromosomes.
B) Sex chromosomes contain a centromere and a telomere at each end.
C) Sex chromosomes are also called autosomes.
D) In humans, the Y chromosome is always inherited from the male parent.

Question 18

Heterochromatin is

A) condensed, transcriptionally active chromatin.
B) condensed, transcriptionally silent chromatin.
C) decondensed, transcriptionally active chromatin.
D) decondensed, transcriptionally silent chromatin.

Question 19

Which of the following occupies the largest portion of the human genome?

A) protein-coding sequences
B) introns
C) repeat sequences
D) gene regulatory sequences

Question 20

Which of the following accounts for the interspersed locations of LINEs and SINEs in eukaryotic genomes?

A) They arise spontaneously.
B) Selective evolutionary pressure prevents the persistence of local spots of concentrated LINEs or SINEs.
C) LINEs and SINEs are transposable elements that can insert at random positions in the genome.
D) LINEs and SINEs result from random integrations of retroviral DNA.

Question 21

Satellite DNA is a type of

A) transposon.
B) centromere-determining sequence.
C) gene coding sequence.
D) tandem repeat.

Question 22

Most archael genomes

A) contain vast non-coding repeats.
B) are packaged into nucleoids.
C) are maintained as multiple linear chromosomes.
D) encode histone-like proteins.

Question 23

Describe the levels of packing involved in fitting 2 meters of DNA into the nucleus of a eukaryotic cell.

Question 24

The 10 nm chromatin fiber in eukaryotes has been described as "beads on a string." What are the "beads" (be precise and detailed in your use of terminology) and what is the "string"?

Question 25

Compare and contrast key features that distinguish eukaryotic genomes from bacterial genomes.

Question 26

It has been said that the relationship between plasmids and host bacteria could be considered as either parasitic or symbiotic. Discuss this statement.

Question 27

Discuss some of the reasons that DNA viruses have proved extremely useful systems for analysis of fundamental principles of molecular biology.

Question 28

Leber's hereditary optic neuropathy, a form of young adult blindness, is linked to a small inherited mutation in mitochondrial DNA. Discuss some of the reasons why individuals with this disease may have differences in the severity and kinds of symptoms they display.

Question 29

Chloroplast DNA is usually depicted as a circular, double-stranded DNA molecule. Is this depiction correct? Explain your answer.

Question 30

Although mitochondria in both plants and animals are thought to have derived from the same ancient prokaryote and carry out the same essential functions, the size of mtDNA varies dramatically between modern animal and plant species. How can these observations be reconciled?

Question 31

Brief digestion of eukaryotic chromatin with micrococcal nuclease gives DNA fragments ~200 bp long. You repeat the experiment, but incubate the samples for a longer period of time while you are in class. This longer digestion yields 146 bp fragments. Why?

Question 32

Do the 10 nm and 30 nm eukaryotic chromatin fibers exist in vivo? Discuss electron microscopic and biochemical evidence in support of your answer.

Question 33

Discuss the characteristics of polytene chromosomes that make them useful for the study of genes and gene expression.