Section 1
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What is the primary difference in genome size between eukaryotes and prokaryotes?
Eukaryotic genomes are larger and more complex than prokaryotic genomes This size difference is not directly related to genetic complexity.
Approximately how many protein-coding genes does the human genome contain?
About 20,000 protein-coding genes This is fewer than the previously predicted 100,000 genes.
What percentage of the average human gene is made up of introns?
Approximately 93% Protein-coding sequences account for only about 3% of the average human gene.
True or false: Introns are present in almost all genes of complex eukaryotes.
TRUE However, introns are not universal; for example, genes encoding histones lack introns.
What are nested genes?
A gene contained within an intron of a larger gene Nested genes can encode proteins or noncoding RNAs.
What is the role of introns in gene expression?
• Regulate gene expression • Allow for alternative splicing Introns contain regulatory sequences critical for cell behavior.
What is alternative splicing?
The process that allows different proteins to be encoded by a single gene Approximately 90% of human genes can undergo alternative splicing.
What are transposable elements?
DNA sequences that can move to different sites in the genome Examples include SINEs and LINEs.
How do SINEs and LINEs move within the genome?
Through reverse transcription They are classified as retrotransposons.
What percentage of human DNA is made up of retrovirus-like elements?
Approximately 8% There are about 450,000 retrovirus-like elements in the human genome.
What is the function of DNA transposons?
Move through the genome by being copied and reinserted as DNA sequences They account for about 3% of human DNA.
What is the average number of exons in a human gene?
About 10 exons The total length of exons averages 4.3 kb.
Fill in the blank: The Human Genome Project reported its first draft sequence in _______.
2004 This project revealed significant insights about the human genome.