Multiple Choice
Which of the following is true regarding reverse transcriptase?
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16. Transposable Elements
Transposable Elements in Eukaryotes
1:49 minutesProblem 9
Textbook Question
The human genome contains a large number of pseudogenes. How would you distinguish whether a particular sequence encodes a gene or a pseudogene? How do pseudogenes arise?
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Understand the definition of pseudogenes: Pseudogenes are non-functional sequences in the genome that resemble functional genes but have lost their ability to encode proteins due to mutations or other changes.
To distinguish between a gene and a pseudogene, analyze the sequence for key features of functional genes, such as the presence of an intact open reading frame (ORF), regulatory elements (e.g., promoters), and splice sites. Pseudogenes often lack these features or have mutations disrupting them.
Perform comparative genomic analysis: Compare the sequence in question to known functional genes. Pseudogenes often show high sequence similarity to functional genes but may contain stop codons, frameshift mutations, or deletions that prevent proper protein synthesis.
Investigate transcriptional activity: Use techniques like RT-PCR or RNA sequencing to determine if the sequence is transcribed into RNA. Functional genes are typically transcribed, while pseudogenes may not be actively transcribed or produce non-functional RNA.
Understand how pseudogenes arise: Pseudogenes can originate through processes such as gene duplication followed by mutation (resulting in non-functional copies) or retrotransposition, where reverse-transcribed RNA is inserted back into the genome without proper regulatory elements.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Gene vs. Pseudogene
A gene is a sequence of DNA that encodes a functional product, typically a protein, while a pseudogene is a non-functional sequence that resembles a gene but has lost its ability to be expressed. Pseudogenes can arise from mutations that disrupt the coding sequence or regulatory elements necessary for gene expression, rendering them inactive.
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Functional Analysis
To distinguish between a gene and a pseudogene, functional analysis is crucial. This involves examining the sequence for features such as open reading frames (ORFs), promoter regions, and conservation across species. If a sequence lacks these features or shows signs of degradation, it is likely a pseudogene.
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Mechanisms of Pseudogene Formation
Pseudogenes can arise through several mechanisms, including gene duplication, retrotransposition, and point mutations. Gene duplication creates a copy of a gene that may accumulate mutations over time, while retrotransposition involves the reverse transcription of mRNA into DNA, which can insert non-functional copies into the genome.
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