Molecular Cell Biology

Harvey Lodish, Arnold Berk, Chris A. Kaiser

Chapter 6

Genes, Genomics, and Chromosomes - all with Video Answers

Educators

Chapter Questions

Problem 1

Genes can be transcribed into mRNA for protein-coding genes or into RNA for genes such as ribosomal or transfer RNAs. Define a gene. For the following characteristics, state whether they apply to (a) continuous, (b) simple, or (c) complex transcription units.
(i) Found in eukaryotes
(ii) Contain introns
(iii) Only capable of making a single protein from a given gene

Alex Thoms

Alex Thoms

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Problem 1

Genetic mutations can provide insights into the mechanisms of complex cellular or developmental processes. How might your analysis of a genetic mutation be different depending on whether a particular mutation is recessive or dominant?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 2

What is a temperature-sensitive mutation? Why are temperature-sensitive mutations useful for uncovering the function of a gene?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 2

Sequencing of the human genome has revealed much about the organization of genes. Describe the differences between solitary genes, gene families, pseudogenes, and tandemly repeated genes.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 3

Describe how complementation analysis can be used to reveal whether two mutations are in the same or in different genes. Explain why complementation analysis will not work with dominant mutations.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 3

Much of the human genome consists of repetitious DNA. Describe the difference between microsatellite and minisatellite DNA. How is this repetitious DNA useful for identifying individuals by the technique of DNA fingerprinting?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 4

Jane has isolated a mutant strain of yeast that forms red colonies instead of the normal white when grown on a plate. To determine the mutant gene, she decides to use functional complementation with a DNA library containing a lysine selection marker. In addition to the unknown gene mutation, the yeast are lacking the gene required to synthesize the amino acids leucine and lysine. What media will Jane grow her yeast on to ensure that they have acquired the library plasmids? How will she know when a library plasmid has complemented her yeast mutation?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 4

Mobile DNA elements that can move or transpose to a new site directly as DNA are called DNA transposons. Describe the mechanism by which a bacterial DNA transposon, called an insertion sequence, can transpose.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 5

Retrotransposons are a class of mobile elements that transpose via an $\mathrm{RNA}$ intermediate. Contrast the mechanism of transposition between retrotransposons that contain long terminal repeats (LTRs) and those that lack LTRs.

Rabeya Zahid

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Problem 6

Discuss the role that transposons may have played in the evolution of modern organisms. What is exon shuffling? What role do transposons play in the process of exon shuffling?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 7

Mitochondria and chloroplasts are thought to have evolved from symbiotic bacteria present in nucleated cells. What is the experimental evidence from this chapter that supports this hypothesis?

Dennis Howard

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Problem 8

What are paralogous and orthologous genes? What are some of the explanations for the finding that humans are a much more complex organism than the roundworm C. elegans, yet have only fewer than one and a half as many genes
$(25,000 \text { versus } 18,000) ?$

Rabeya Zahid

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Problem 9

The DNA in a cell associates with proteins to form chromatin. What is a nucleosome? What role do histones play in nucleosomes? How are nucleosomes arranged in condensed 30 -nm fibers?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 10

How do chromatin modifications regulate transcription? What modifications are observed in regions of the genome that are actively being transcribed? What about for regions that are not actively transcribed?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 11

Describe the general organization of a eukaryotic chromosome. What structural role do scaffold-associated regions (SARs) or matrix attachment regions (MARs) play? Why does it make sense that protein-coding genes are not located in these regions?

Rabeya Zahid

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Problem 12

What is FISH? Briefly describe how it works. How is FISH used to characterize chromosomal translocations associated with certain genetic disorders and specific types of cancers?

Rabeya Zahid

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Problem 13

What is chromosome painting, and how is this technique useful? How can chromosome paint probes be used to analyze the evolution of mammalian chromosomes?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 14

Certain organisms contain cells that possess polytene chromosomes. What are polytene chromosomes, where are they found, and what function do they serve?

Rabeya Zahid

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Problem 15

Replication and segregation of eukaryotic chromosomes require three functional elements: replication origins, a centromere, and telomeres. How would a chromosome be affected if it lacked (a) replication origins or (b) a centromere?

Rabeya Zahid

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Problem 16

Describe the problem that occurs during DNA replication at the ends of chromosomes. How are telomeres related to this problem?

Rabeya Zahid

Numerade Educator