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Introduction to DNA Quiz
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Which statement best defines a gene in humans?
- A A region of DNA that codes for a single amino acid You picked ✕
- B A region of DNA that is spliced out of messenger RNA before translation You picked ✕
- C An intergenic DNA region with no demonstrated transcript or regulatory function You picked ✕
- D A region of DNA that encodes a protein or a functional RNA You picked ✓
- E A region of DNA that is inherited unchanged from one generation to the next You picked ✕
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Incorrect
The answer is D: A region of DNA that encodes a protein or a functional RNA
Explanation
Why D is correct
See Genes. Option D is correct because a gene is a region of DNA that encodes a functional product, and that product is either a protein or a functional RNA. Most genes are transcribed into messenger RNA (mRNA, the copy that carries instructions for a protein) and then translated into protein, but some genes make RNAs that work as RNA, such as the ribosomal RNA and transfer RNA used by ribosomes. This wider definition is why a gene is defined by its product rather than only by coding for protein. Each gene has a fixed address on a chromosome, called its locus. Humans have around 25,000 genes spread across 23 pairs of chromosomes, which are 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes. Memory aid: a gene is a recipe, the protein or RNA is the dish, and the chromosome is the cookbook that holds many recipes.
- Definition: a gene is a region of DNA that encodes a functional product.
- Products: most genes make mRNA and then protein, but some make RNAs that work as RNA, such as ribosomal RNA and transfer RNA.
- Locus: each gene has a fixed address on a chromosome.
Why the other options are incorrect
- A. A region of DNA that codes for a single amino acid: A gene codes for a whole product, not a single amino acid. The unit that specifies one amino acid is a codon, which is a three-base sequence within the gene. Your answer
- B. A region of DNA that is spliced out of messenger RNA before translation: Splicing removes intronic RNA from the pre-mRNA, not DNA from the messenger RNA. A gene includes both exons and introns and remains in the genome. Your answer
- C. An intergenic DNA region with no demonstrated transcript or regulatory function: An intergenic region with no transcript or regulatory function is by definition not a gene. A gene is a DNA region that produces a functional product. Your answer
- E. A region of DNA that is inherited unchanged from one generation to the next: Genes are not inherited unchanged; DNA sequence can be altered by mutation and recombination. This statement describes a false idea of perfect conservation rather than what a gene is. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which statement best explains why genes located in euchromatin are more transcriptionally active than those in heterochromatin?
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2
Which statement best describes base pairing within the DNA double helix?
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