Chat with AIExam 16: Genome Analysis: DNA Typing, Genomics, and Beyond
The Japanese pufferfish (Takifugu rubripes) genome is approximately eight times smaller than the human genome, but contains just as many protein-coding genes. How can that be?
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Answered by Examlex AI CopilotThe Japanese pufferfish (Takifugu rubripes), also known as fugu, has a genome that is significantly smaller than the human genome, yet it contains a comparable number of protein-coding genes. This can be explained by several factors that contribute to the differences in genome size without affecting the number of essential genes:
1. **Non-coding DNA:** A large portion of the human genome is made up of non-coding DNA, which includes introns within genes, regulatory sequences, and a vast amount of repetitive sequences that do not code for proteins. In contrast, the pufferfish genome has a much smaller proportion of non-coding DNA. It has been streamlined through evolutionary processes, resulting in shorter introns and fewer repetitive elements.
2. **Gene Density:** The pufferfish genome has a higher gene density compared to the human genome. This means that the genes are packed more closely together, with less non-coding DNA separating them. As a result, the same number of genes occupies a smaller amount of genomic space.
3. **Genome Efficiency:** The pufferfish genome is thought to be more efficient in some ways. It has undergone extensive DNA deletions and reductions over evolutionary time, which has led to the loss of non-essential DNA sequences without compromising the essential protein-coding genes.
4. **Genome Evolution:** Different species have evolved different genome sizes and structures based on their unique evolutionary pressures and histories. The compact genome of the pufferfish may reflect an adaptation to its specific environmental conditions or life history traits.
5. **Regulatory Elements:** While the number of protein-coding genes may be similar, the complexity of an organism is not determined solely by the number of these genes. It is also influenced by the regulatory elements that control when, where, and how genes are expressed. Humans may have a more complex array of regulatory sequences, contributing to the larger genome size and allowing for more intricate regulation of gene expression.
In summary, the Japanese pufferfish genome demonstrates that a smaller genome size does not necessarily equate to a lesser number of protein-coding genes. Instead, it highlights the importance of non-coding DNA in contributing to genome size and the evolutionary processes that can streamline a genome while preserving its essential coding capacity.
In a study that involved 100 Caucasian males, you find a polymorphism in a gene for a neurotransmitter receptor. The "long allele" is linked with reckless behavior. What conclusions, if any, can you draw about the results of this study? Should you hold a press conference to announce the discovery of the "reckless" gene?
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VerifiedOne can only conclude that the genetic cause of reckless behavior is closely linked with the neurotransmitter receptor, most likely residing in the same haplotype block. It is necessary to conduct further experiments to support a causal role for the long allele, and you should not hold a press conference announcing the neurotransmitter receptor as the "reckless" gene.
Based on the DNA fingerprinting (minisatellite analysis with a multilocus probe) results shown in the figure below, is Mr. X or Mr. Y the child's father? Explain your answer.
(47) VerifiedMr. X is the child's father. There is a simple Mendelian pattern of inheritance. For a child, 50% of the bands are derived from the mother and 50% are derived from the father. The bands that come from the mother can be identified; the remaining bands must come from the father, and these match the bands present in the lane representing Mr. X.
Which two types of genomic variation have been commonly analyzed in genome-wide association studies?
(38) An expectation that has been borne out by comparative genomic analysis is that:
(34) You separate a mixture of proteins by 2D-PAGE. From one protein spot, you obtain the following peptide sequence by mass spectrometry:
EQAGGDATENFEDVGHSTDAR
Use the BLAST tool to identify the unknown protein.
(43) Genome-wide association studies are used for identifying the causes of
(31) What evidence do molecular biologists use to infer that a gene is part of a gene family?
(30) Diagram the process of peptide mass fingerprinting using MALDI-TOF. What type of information can be obtained from this method?
(41) You have characterized the entire proteome of a particular organelle. What further analysis would you do to confirm localization of the identified proteins to this organelle in situ?
(37) About 60% of the human genome is composed of intergenic DNA. Describe two types of intergenic DNA that are used in DNA typing and how they are used.
(39) A cigarette butt found at the scene of a violent crime is found to have a sufficient number of epithelial cells stuck to the paper for the DNA to be extracted and typed. Shown below are the results of typing for three probes (locus 1, locus 2, and locus 3) of the evidence (X) and 4 suspects (A through D). Which of the suspects can be excluded? Which cannot be excluded? Can you identify the criminal? Explain your reasoning.
(33) The variable number of short tandem repeats in the human genome primarily results from
(44) When is a sequence considered a "rough draft" as opposed to a "finished" sequence? Does a genome sequence have to be 100% complete and accurate to be declared "finished"?
(37) Variable number tandem repeats in the promoter region of the monoamine oxidase A gene have been linked to aggressive, impulsive, and violent behavior. A child has been classified as having the 3-repeat, low activity allele. Are they likely to show antisocial behavior as adults? Does this example support the statement "DNA is destiny?"
(44) cDNA derived from normal cell mRNA was labeled with a green fluorescent tag (represented as black). cDNA derived from diseased cell mRNA was labeled with a red fluorescent tag (represented as white; the presence of both green and red tags is represented by stripes). The labeled cDNAs were mixed and hybridized to a prepared DNA microarray. Results from a small section of the microarray grid are shown below. Which genes would you select for further analysis? Explain your answer.
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