Deck 11: Chromosome Structure

Question 1

What is the function of interchromosomal domains in gene transcription?

A)These domains separate chromosome territories and are areas of active transcription.
B)These domains act as regions for formation of chiasmata during crossing over.
C)These domains act as gene-rich regions positioned toward the nuclear membrane to maximize gene transcription.
D)These domains contain no chromatin and act as channels for the movement of proteins,RNAs,and enzymes among the chromosomal territories.
E)These domains act as the regions of the chromosome recognized during meiosis when homologous chromosomes are matched up and aligned at the metaphase I plate.

Answer 1

D

Question 2

Which histone protein is not part of the nucleosome structure?

A)H1
B)H2A
C)H2B
D)H3
E)H4

Answer 2

A

Question 3

You are trying to take a biopsy and prepare a karyotype from an ovary cell,but you accidentally selected an ovum instead.How many pairs of chromosomes are found in the karyotype of a typical human ovum?

A)0
B)22
C)23
D)44
E)46

Answer 3

A

Question 4

You have identified a chromosome that has both p and q arms,but notice that the p arms are composed of highly repetitive DNA.What type of chromosome is this?

A)metacentric
B)submetacentric
C)acrocentric
D)subacrocentric
E)telocentric

Question 5

Typically,methylation of nucleosome N-terminal tails leads to

A)removal of the protein components of the chromatin from the DNA.
B)relaxed packaging of the chromatin and increased transcription.
C)tighter packaging of the chromatin and reduced transcription.
D)increased amounts of euchromatin relative to heterochromatin.
E)activation of topoisomerase.

Question 6

You are trying to prepare a DNA karyotype,but this time you forgot to add trypsin to your chromosome preparation.What effect would you expect to see?

A)Dyes would stain the chromosomes darker because more proteins are present to take up the dye.
B)Dyes would not stain the chromosomes as expected,because proteins would not be removed from the chromatin and so would block the dye from accessing the DNA.
C)Chromosomes do not condense properly,so it would be very difficult to isolate individual chromosomes.
D)Chromosomes would be degraded quickly because the trypsin is necessary to promote DNA stability by adding more scaffold proteins to the chromatin.
E)The chromosomes would be more difficult to pair up because the trypsin acts as a dye,creating a banding pattern that distinguishes between chromosomes.

Question 7

Where are bacterial chromosomes located within the cell?

A)nucleus
B)nucleoid
C)nucleolus
D)cytoplasm
E)mitochondria

Question 8

Typically,acetylation of histone tails leads to

A)removal of the protein components of the chromatin from the DNA.
B)relaxed packaging of the chromatin and increased transcription.
C)tighter packaging of the chromatin and reduced transcription.
D)increased amounts of euchromatin relative to heterochromatin.
E)activation of topoisomerase.

Question 9

You have isolated DNA from actively replicating cells.Where would you expect to find this DNA on a gel?

A)DNA would be highly supercoiled and would be found in the band seen in the positive pole (bottom)of Lane 1.
B)DNA would be predominantly relaxed and would be found in the band seen in the positive pole (bottom)of Lane 1.
C)DNA would be highly supercoiled and would be found in the band seen in the negative pole (top)of Lane 1.
D)DNA would be predominantly relaxed and would be found in the band seen in the negative pole (top)of Lane 1.
E)DNA would be both relaxed and supercoiled,so it would appear in a pattern similar to Lane 2.

Question 10

A cell can form 10-nm chromatin fibers,but not 30-nm fibers.Which molecule has likely been removed or mutated in this cell?

A)H1
B)H2A
C)H3
D)topoisomerase
E)SMC proteins

Question 11

Under normal cellular conditions,what is the diameter of the chromatin as it forms the solenoid structure?

A)3 nm
B)10 nm
C)30 nm
D)34 nm
E)100 nm

Question 12

You have isolated DNA for PCR and accidentally added topoisomerase instead of polymerase to your sample.What would you expect if you ran this DNA sample on a gel?

A)The DNA would show increased supercoiling and have a lower electrophoretic mobility.
B)The DNA would show decreased supercoiling and have a higher electrophoretic mobility.
C)The DNA would show increased supercoiling and have a higher electrophoretic mobility.
D)The DNA would show decreased supercoiling and have a lower electrophoretic mobility.
E)The DNA would show decreased supercoiling,but electrophoretic mobility will be unaffected.

Question 13

How many pairs of chromosomes are found in a typical human somatic cell's karyotype?

A)0
B)22
C)23
D)44
E)46

Question 14

How might a thermophilic bacterium use chromosome structure to protect against heat-induced DNA degradation?

A)It expresses excess amounts of SMC proteins that allow the DNA to more tightly condense during periods of high heat.
B)It can express a specialized topoisomerase that induces negative supercoiling,which provides additional chromosomal stability.
C)It expresses a specialized topoisomerase that induces positive supercoiling,which provides additional chromosomal stability.
D)It expresses enzymes that inhibit topoisomerase during high heat,which prevents DNA from unwinding and becoming susceptible to heat degradation.
E)It expresses helicase,an enzyme that nicks the DNA helix and allows it to assume a more stable conformation and thus to resist heat-induced degradation.

Question 15

The flies with variegated eye color had what abnormal chromosome structure?

A)X-chromosome inversion that moves the w⁺ gene to a different orientation on the chromosome in some cells following x-ray exposure
B)X-chromosome translocation that moves the w⁺ gene to a region of heterochromatin on another chromosome in some cells following x-ray exposure
C)a mutation in the w⁺ gene following x-ray exposure that causes the gene to be overexpressed in a tissue-specific manner
D)X-chromosome deletion that deleted the w⁺ gene in some cells following x-ray exposure
E)a mutation in a somatic chromosome that causes the w⁺ gene to be translocated to the X-chromosomes following x-ray exposure

Question 16

What technique would you use to detect a target sequence in an intact chromosome using a labeled molecular probe?

A)PCR
B)in situ hybridization
C)western blotting
D)Sanger sequencing
E)karyotyping

Question 17

Which type of chromosome has no p arms?

A)metacentric
B)submetacentric
C)acrocentric
D)subacrocentric
E)telocentric

Question 18

Active transcription occurs in regions of chromatin loops that are located

A)near the MARS.
B)a large distance away from the MARS.
C)within the linker DNA.
D)within the telomeres.
E)within the euchromatin and constitutive heterochromatin.

Question 19

A bacterium inherits a mutation that renders its topoisomerase enzyme nonfunctional.What phenotype would you expect to see in this bacterium?

A)The cell would accumulate broken DNA because overwinding cannot be corrected,so the cell will be unable to replicate and will die.
B)The cell would accumulate supercoiled DNA,but otherwise it is perfectly normal.
C)The cell would accumulate relaxed DNA,which would make DNA replication and cell division highly disorganized and lead to cell death.
D)The cell would accumulate relaxed DNA,but otherwise it is perfectly normal.
E)The cell would be unaffected because bacteria have many different topoisomerases that are involved in replication.

Question 20

What is meant by the "beads on a string" model of chromatin?

A)The beads are the histones,and the string is the transcriptionally active DNA loops.
B)The beads are the nucleosomes,and the string is the linker DNA.
C)The beads are molecules of DNA polymerase that attach to the DNA string.
D)The beads are ribosomes,and the string is the mRNA that has been transcribed from active chromatin.
E)The beads are the heterochromatic regions that are tightly compacted,and the strings are euchromatic regions that are being actively transcribed.

Question 21

Which proteins would you target if you wanted to disrupt the chromosome superstructure for chromatin condensation that ultimately produces the characteristic shape of the metaphase chromosome?

Question 22

What molecular interaction allows histones to interact with DNA?

Question 23

Nonhistone proteins make up the protein framework that gives the chromosomes their shape.What is this structure called?

Question 24

You are attempting to isolate cells for your karyotype,and you find one cell in each of the phases (prophase,metaphase,anaphase,and telophase).Which one is best suited for a karyotype?

Question 25

Nucleosome displacement during transcription initiation is referred to as what?

Question 26

What type of DNA supercoiling is the most common?

Question 27

What is the name of the structure formed when the 10-nm fibers of chromatin form a cylindrical filament of coiled nucleosomes?

Question 28

If you want to prevent chromatin loops from being anchored to the chromosome scaffold,which regions of the DNA would you target?

Question 29

Karyotypes are a method for displaying chromosomes by grouping them into homologous pairs based on what two distinguishing factors?

Question 30

What is the diameter of a nucleosome?

Question 31

If heterochromatin spreading does not reach the new location of the w⁺ gene,and it remains in the euchromatic region,the gene produces what phenotype?

Question 32

What gene is critical for establishment of X-inactivation in mammals?

Question 33

Chromosome condensation compacts the chromosomes so they can be efficiently separated at which phase of mitosis?

Question 34

To preserve epigenetic memory in the daughter cells,the cell retains these "old" proteins during DNA replication.

Question 35

Which proteins participate in DNA bending and contribute to folding and condensation of the chromosome?

Question 36

What is the purpose of DNA supercoiling?

Question 37

If you block histone deacetylase,what effect would you expect to see on transcriptional activity?

Question 38

Nucleosomes are comprised of how many molecules of histones?

Question 39

What type of chromosome structure is commonly found in hyperthermophiles?

Question 40

If heterochromatic spreading encompasses the new location of the w⁺ gene,what is the phenotype of the cells?

Question 41

________ are extrachromosomal DNA molecules that are not part of the bacterial genome.

Question 42

What are the common types of epigenetic modifications? Describe how epigenetic modifications can assist in predicting whether a gene is active or inactive in a cell.

Question 43

Eukaryotic chromosomes are a combination of proteins and DNA,which allows the cell to perform which four essential functions?

Question 44

The total amount of hereditary information in an entire set of chromosomes is collectively referred to as an organism's ________.

Question 45

Each nucleus in a human somatic cell contains ________ chromosomes.

Question 46

Quinolones are a group of broad-spectrum antibiotics that specifically target topoisomerase.Explain how this contributes to cell death in bacteria.Would you expect these drugs to kill hyperthermophilic prokaryotes too? Why or why not?

Question 47

Tortoiseshell cats have a coat-color gene on their X chromosome.What process in eukaryotes explains why males can have solid orange or black fur,and only females can have the tortoiseshell pattern of fur?

Question 48

Histone deacetylase (HDAC)inhibitors are commonly used as mood stabilizers or in the treatment of neurodegenerative diseases.What effect would a HDAC inhibitor have on the target cells?

Question 49

The DNA-protein complex that comprises eukaryotic chromosomes is called ________.

Question 50

Given what you know about coat color in cats,list the possible genotypes for these individuals:
• orange male
• orange female
• black male
• black female
• tortoiseshell

Question 51

The ability of DNA-binding proteins to initiate transcription can be hindered by the presence of ________ on the promoter regions of the DNA.