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Questions and Answers
Each of the following statements about conserved and nonconserved regions in a comparison of mouse and human genomes is true EXCEPT:
Each of the following statements about conserved and nonconserved regions in a comparison of mouse and human genomes is true EXCEPT:
Roughly half of the DNA in the human genome consists of repeated sequences.
Roughly half of the DNA in the human genome consists of repeated sequences.
What is the term for the evolutionary process that eliminates individuals carrying mutations that interfere with important genetic functions?
What is the term for the evolutionary process that eliminates individuals carrying mutations that interfere with important genetic functions?
To complete the table, what number should be written in place of the question marks for the comparison of fish and whale?
To complete the table, what number should be written in place of the question marks for the comparison of fish and whale?
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Are all of the exons of the human β-globin gene (indicated by shading in Part A) homologous to the mouse β-globin gene? How would you explain any discrepancies if present?
Are all of the exons of the human β-globin gene (indicated by shading in Part A) homologous to the mouse β-globin gene? How would you explain any discrepancies if present?
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Assuming that substitutions occurred at the same rate in the duplicated sequences generated by these Alu insertions, how long ago did this group of Alu sequences insert into these genes?
Assuming that substitutions occurred at the same rate in the duplicated sequences generated by these Alu insertions, how long ago did this group of Alu sequences insert into these genes?
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Multispecies sequence comparisons have revealed large numbers of so-called multispecies conserved sequences, the majority of which code for proteins.
Multispecies sequence comparisons have revealed large numbers of so-called multispecies conserved sequences, the majority of which code for proteins.
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Which one of the following statements correctly describes what has been learned in studies of chromosomal sequences that have been conserved during mammalian evolution but have been deleted from the human genome in the six million years since humans and chimpanzees diverged?
Which one of the following statements correctly describes what has been learned in studies of chromosomal sequences that have been conserved during mammalian evolution but have been deleted from the human genome in the six million years since humans and chimpanzees diverged?
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- Reception of extracellular signals
2. Post-translational protein modification
3. Development and transcription regulation
In which order did these major regulatory innovations occur during vertebrate evolution, from earliest to latest?
- Reception of extracellular signals 2. Post-translational protein modification 3. Development and transcription regulation
In which order did these major regulatory innovations occur during vertebrate evolution, from earliest to latest?
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What is the basis for the variable intensity of hybridization of RsaI-A genes in males with normal color vision?
What is the basis for the variable intensity of hybridization of RsaI-A genes in males with normal color vision?
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What is the term for a copy of a functional gene that has become irreversibly inactivated by multiple mutations?
What is the term for a copy of a functional gene that has become irreversibly inactivated by multiple mutations?
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About 500 million years ago, the original globin gene was duplicated and mutated to form two slightly different genes encoding proteins that could form a hemoglobin molecule containing two α and two β chains (see the figure). Why is this event considered such an important evolutionary advance?
About 500 million years ago, the original globin gene was duplicated and mutated to form two slightly different genes encoding proteins that could form a hemoglobin molecule containing two α and two β chains (see the figure). Why is this event considered such an important evolutionary advance?
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How does the presence of long introns affect such duplication events?
How does the presence of long introns affect such duplication events?
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Which one of the following orders correctly ranks the rate—from fastest to slowest—at which deleterious, advantageous, and neutral mutations would be expected to spread through a population?
Which one of the following orders correctly ranks the rate—from fastest to slowest—at which deleterious, advantageous, and neutral mutations would be expected to spread through a population?
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How many single nucleotide differences do you suppose would be found in a comparison of the genomes from two unrelated individuals?
How many single nucleotide differences do you suppose would be found in a comparison of the genomes from two unrelated individuals?
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Which one of the following statements correctly characterizes a property of the variants discovered by comparing the genome sequences from many individuals?
Which one of the following statements correctly characterizes a property of the variants discovered by comparing the genome sequences from many individuals?
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From which, if any, of the individuals did the drop of blood at the crime scene originate?
From which, if any, of the individuals did the drop of blood at the crime scene originate?
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Each of the following changes to the genome is likely to cause genetic disease EXCEPT:
Each of the following changes to the genome is likely to cause genetic disease EXCEPT:
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What is the term describing the relative orientation of the two strands in a DNA helix, when the polarity of one strand is oriented in the opposite direction to that of the other strand?
What is the term describing the relative orientation of the two strands in a DNA helix, when the polarity of one strand is oriented in the opposite direction to that of the other strand?
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What happens to the two strands of a DNA molecule during replication?
What happens to the two strands of a DNA molecule during replication?
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Which of the following chromosomal events has led to this abnormal karyotype?
Which of the following chromosomal events has led to this abnormal karyotype?
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What is the term for a DNA sequence that produces a functional RNA—structural, catalytic, or regulatory—or encodes a protein (or a set of closely related protein isoforms)?
What is the term for a DNA sequence that produces a functional RNA—structural, catalytic, or regulatory—or encodes a protein (or a set of closely related protein isoforms)?
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Using these numbers, how many protein-coding genes would you estimate for the haploid human genome?
Using these numbers, how many protein-coding genes would you estimate for the haploid human genome?
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The DNA of human mitotic chromosomes is highly condensed; the DNA of human interphase chromosomes is fully extended.
The DNA of human mitotic chromosomes is highly condensed; the DNA of human interphase chromosomes is fully extended.
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Do these results suggest that the Martian organism has nucleosome-like structures in its chromatin? If so, what can you deduce about their spacing along the DNA?
Do these results suggest that the Martian organism has nucleosome-like structures in its chromatin? If so, what can you deduce about their spacing along the DNA?
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Given the dynamic structure of the nucleosome, which one of the following effects is most important for determining the exact positions of nucleosomes along a stretch of DNA at any time in the cell?
Given the dynamic structure of the nucleosome, which one of the following effects is most important for determining the exact positions of nucleosomes along a stretch of DNA at any time in the cell?
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Which one of the following proteins is called the linker histone?
Which one of the following proteins is called the linker histone?
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Which one of the following forms of chromatin is the most common in a mammalian cell?
Which one of the following forms of chromatin is the most common in a mammalian cell?
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Does trypsin treatment of nucleosome monomers appear to render a random population or a specific population of nucleosomes sensitive to micrococcal nuclease? How can you tell?
Does trypsin treatment of nucleosome monomers appear to render a random population or a specific population of nucleosomes sensitive to micrococcal nuclease? How can you tell?
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Phosphorylation of serine and acetylation of lysine in histone tails would both be expected to alter the interaction of the histone tails with DNA. Would these histone modifications be expected to increase or decrease the interaction of the histone with DNA?
Phosphorylation of serine and acetylation of lysine in histone tails would both be expected to alter the interaction of the histone tails with DNA. Would these histone modifications be expected to increase or decrease the interaction of the histone with DNA?
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Which one of the following statements about histone variants is correct?
Which one of the following statements about histone variants is correct?
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Which of the following statements about histone marks on nucleosomes are correct?
I The combinations of modifications to histone tails constitute a well-defined histone code.
II Because histone tails extend outward from nucleosomes, they are accessible except in condensed chromatin.
III The marks on nucleosomes due to covalent changes to histones are dynamic, being constantly removed and added.
Which of the following statements about histone marks on nucleosomes are correct?
I The combinations of modifications to histone tails constitute a well-defined histone code. II Because histone tails extend outward from nucleosomes, they are accessible except in condensed chromatin. III The marks on nucleosomes due to covalent changes to histones are dynamic, being constantly removed and added.
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Based on these results, which of the tested proteins binds to the unmodified tails of histones H3 and H4?
Based on these results, which of the tested proteins binds to the unmodified tails of histones H3 and H4?
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Which one of the following statements best explains the function of the E and I sites?
Which one of the following statements best explains the function of the E and I sites?
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Which one of the following descriptions applies to both the inheritance of heterochromatin and its spreading along the chromosome?
Which one of the following descriptions applies to both the inheritance of heterochromatin and its spreading along the chromosome?
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Which of the following modifications could explain the lack of p16 protein in these cancer cells?
I Formation of euchromatin at the p16 genes
II Formation of heterochromatin at the p16 genes
III Modification of histone tails at the p16 genes
Which of the following modifications could explain the lack of p16 protein in these cancer cells?
I Formation of euchromatin at the p16 genes II Formation of heterochromatin at the p16 genes III Modification of histone tails at the p16 genes
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Study Notes
Conserved and Nonconserved Regions
- About half of the human genome consists of repeated sequences.
- Multispecies sequence comparisons reveal a vast number of conserved sequences, mainly coding for proteins.
- Discrepancies in homologous exons between human and mouse β-globin genes indicate evolutionary variation.
Evolutionary Processes
- Natural selection eliminates individuals with harmful mutations affecting key genetic functions.
- Functional gene copies can become irreversibly inactivated due to multiple mutations.
Genetic Innovations and Comparisons
- Studies indicate mammalian evolution has conserved sequences related to cell signaling, protein modification, and regulation of development and transcription.
- The order of regulatory innovations includes reception of signals first, followed by protein modification and transcription regulation.
Genetic Variability
- Single nucleotide differences exist between the genomes of two unrelated individuals; the number may vary widely but indicates human genetic diversity.
- Variants discovered through genome comparison illustrate population diversity and adaptation.
DNA Structure and Replication
- The DNA helix has antiparallel strands, each oriented in opposite directions.
- During replication, the two strands separate, serving as templates for new strand synthesis.
Chromosomal Events
- Abnormal karyotypes can arise from chromosomal events like duplications or deletions.
- Functional RNA or protein-coding DNA sequences are essential for various biological functions.
Human Genome Estimates
- Estimating protein-coding genes in the haploid human genome suggests thousands of potential genes based on the reference sequences.
Chromatin Structure
- Human chromosomes are highly condensed during mitosis and fully extended in interphase, signaling active and inactive genetic regions.
- The presence of nucleosome-like structures in alien organisms can suggest similar chromatin functions.
Histones and Nucleosomes
- Linker histones play a critical role in the arrangement of nucleosomes along DNA.
- Nucleosomes are dynamic, with histone tails affected by phosphorylation and acetylation, influencing interaction with DNA.
- Histone modifications form a dynamic 'histone code,' essential for regulating gene expression.
Cancer Cell Behavior
- Abnormal p16 protein expression in cancer cells may result from alterations in chromatin formation and histone modifications.
Conclusion
- A comprehensive understanding of genomic structure, sequence conservation, and the evolution of regulatory mechanisms is crucial for grasping biological functions and the basis of genetic diseases.
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Description
Test your knowledge on genomic comparisons, evolutionary processes, and homologous genes with this quiz. Questions cover topics such as conserved and nonconserved regions, repeated sequences in the human genome, homologous genes, and the evolutionary process of eliminating individuals carrying mutations.
