Chapter 12

Polytene chromosomes:  

•  

  are found in all somatic eukaryotic cells.

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  represent multiple copies of paired homologs.

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  cannot be seen in interphase cell nuclei.

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  have different random banding patterns in different individuals.

Lampbrush chromosomes are an unusual type of chromosome that:

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  contain a single strand of DNA.

•  

  become tightly condensed during cell division.

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  are found in meiotic cells.

•  

  are not transcriptionally active.

Which of the following describes the order of DNA compaction in chromosomes from least compact to most compact?

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  Nucleosomes, 30nm fiber, looped domains, chromatid fiber, chromatid

•  

  30nm fiber, nucleosomes, chromatid fiber, looped domains, chromatid

•  

  Chromatid, chromatid fiber, looped domains, 30nm fiber, nucleosomes

•  

  Looped domains, nucleosomes, 30nm fiber, chromatid, chromatid fiber

The cell cycle is regulated by kinases, which are enzymes that ____________ histones and affect chromosome packing at specific times during the cell cycle.

• phosphorylate

• acetylate

• degrate

• methylate

Middle repetitive DNA sequences can be used for DNA fingerprinting because they differ among individuals in the:

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  proteins that bind to the repeated sequences.

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  length of the repeated sequence.

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  DNA modifications of the repeated sequences.

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  location of the repeated sequence.

Approximately what percentage of the human genome is comprised of functional genes?

• 2%

• 50%
• 20%

• 5%

Methylation of DNA usually has what effect?

•  

  Chromatin becomes less compact and genes are less active

•  

  Chromatin becomes more compact and genes are less active

•  

  Chromatin becomes more compact and genes are more active

•  

  Chromatin becomes less compact and genes are more active

Acetylation of histones usually has what effect?

• Decreases gene expression
• Inhibits transcription factors
• Has no effect on gene expression
• Increases gene expression chromatin become less compact

In eukaryotes, DNA is organized around proteins called ______.

• histones
• plasmids
• ribosomes
• chromosomes

Which of the following statements correctly describes the structure of chromatin?

• Euchromatin is highly condensed and inactive, whereas heterochromatin is less compact and more active.

•  

  Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.

•  

  Both heterochromatin and euchromatin are found in the cytoplasm.

•  

  Heterochromatin is highly condensed and inactive, whereas euchromatin is less compact and more active.