501. Which sequence best represents the general workflow of large-scale genome sequencing in the Human Genome Project?
ⓐ. isolate genome DNA → fragment and clone → sequence fragments → align overlaps → annotate sequences
ⓑ. translate proteins → identify codons → build DNA → clone exons → annotate ribosomes
ⓒ. isolate RNA → remove introns → sequence proteins → form chromosomes → annotate cells
ⓓ. digest proteins → copy mRNA → assemble codons → clone amino acids → sequence operons
Correct Answer: isolate genome DNA → fragment and clone → sequence fragments → align overlaps → annotate sequences
Explanation: Genome sequencing follows an ordered strategy rather than a random set of unrelated steps. The genome DNA is first isolated, then broken into manageable pieces and cloned. These fragments are sequenced, their overlaps are assembled computationally, and the final sequence is annotated to identify meaningful regions. This workflow summarizes the core methodological logic of the Human Genome Project.
502. Which limitation best applies to the expressed sequence tags (EST) approach in genome analysis?
ⓐ. It cannot identify any coding sequences.
ⓑ. It may miss genes or regions not expressed in the sampled cells, along with many non-coding regions.
ⓒ. It sequences only ribosomal RNA genes.
ⓓ. It cannot use cDNA at all.
Correct Answer: It may miss genes or regions not expressed in the sampled cells, along with many non-coding regions.
Explanation: EST analysis is based on expressed RNA-derived sequences, so it is biased toward genes active in the sampled tissue or condition. Regions that are not being expressed at that time, as well as many non-coding regions, may be missed. Whole-genome sequencing is broader in this respect. This is a standard comparison question from Human Genome Project methods.
503. Which category of genomic information is most likely to be captured by whole-genome sequencing but missed by an EST-based approach?
ⓐ. non-coding repetitive regions and genes not expressed in the sampled cells
ⓑ. only start and stop codons of ribosomal genes
ⓒ. amino acids attached to tRNA
ⓓ. peptide-bond positions in proteins
Correct Answer: non-coding repetitive regions and genes not expressed in the sampled cells
Explanation: EST analysis is based on expressed transcripts, so it mainly reveals genes that are active in the tissue or condition sampled. It may therefore miss non-coding DNA and genes not being expressed at that time. Whole-genome sequencing, in contrast, covers coding and non-coding regions across the genome. This is one of the main conceptual differences between the two strategies.
504. In a human genome sequencing project, a DNA fragment is sequenced but its biological meaning is still unknown until computational comparison identifies gene-like regions and possible function. This later step is called
ⓐ. replication
ⓑ. aminoacylation
ⓒ. annotation
ⓓ. autoradiography
Correct Answer: annotation
Explanation: Sequencing provides the order of bases, but sequence alone does not automatically reveal biological meaning. Annotation is the process of identifying probable genes, features, and functions from the raw sequence. It is therefore an interpretive step after sequence generation and assembly. This distinction is essential in genome-analysis questions.
505. Which statement correctly describes the size of the human genome in this chapter treatment?
ⓐ. It contains about 3164.7 million base pairs.
ⓑ. It contains about 4.6 million base pairs.
ⓒ. It contains about 48,502 base pairs.
ⓓ. It contains about 5,386 nucleotides.
Correct Answer: It contains about 3164.7 million base pairs.
Explanation: The human genome is presented here as an extremely large DNA system with about 3164.7 million base pairs. This value helps show how much larger the human genome is than bacterial or viral genomes discussed earlier. Such scale was one reason the Human Genome Project required major computational support. It also emphasizes that genome analysis extends far beyond studying a few individual genes.
506. The average size of a human gene in this chapter treatment is about
ⓐ. 300 bases
ⓑ. 3 million bases
ⓒ. 30,000 bases
ⓓ. 3000 bases
Correct Answer: 3000 bases
Explanation: Human genes are described here as having an average size of about 3000 bases. This value is an average and does not mean every gene has exactly that length. Some genes are much smaller, while others are far larger. The number helps build a general picture of genome organization rather than giving a fixed size for all genes.
507. Which human gene is mentioned here as the largest known gene, with a size of about 2.4 million bases?
ⓐ. lacZ
ⓑ. globin
ⓒ. dystrophin
ⓓ. insulin
Correct Answer: dystrophin
Explanation: Dystrophin is highlighted here as the largest known human gene, measuring about 2.4 million bases. This fact shows that gene size can vary enormously within the human genome. It also helps explain why average gene size does not fully describe genome structure. Some genes are exceptionally large and stand out from the general pattern.
508. Around how many genes are described for the human genome in this chapter treatment?
ⓐ. about 3,000
ⓑ. about 30,000
ⓒ. about 300,000
ⓓ. about 3 million
Correct Answer: about 30,000
Explanation: The chapter presents the human genome as containing about 30,000 genes in this treatment. This figure is one of the major summary facts associated with Human Genome Project findings at this level. It also helps correct the mistaken assumption that a very large genome must contain an extremely huge number of genes. Genome size and gene count are related, but not in a simple one-to-one way.
509. Which statement best describes similarity in DNA sequence among different humans?
ⓐ. Humans differ completely in most of their nucleotide sequence.
ⓑ. Less than half of the nucleotide sequence is shared among humans.
ⓒ. About 90% of nucleotide bases are the same in all humans.
ⓓ. About 99.9% of nucleotide bases are the same in all humans.
Correct Answer: About 99.9% of nucleotide bases are the same in all humans.
Explanation: Human beings are genetically very similar at the sequence level, with about 99.9% of nucleotide bases being the same among individuals. This means that the visible and biological differences among people arise from a relatively small fraction of genomic variation. That small variable fraction is still highly important for identity and inherited differences. The figure also provides the basis for understanding polymorphism and DNA fingerprinting later in the chapter.
510. If two human haploid genomes are each about $3.3 \times 10^9$ base pairs long and are 99.9% identical, the approximate number of nucleotide positions at which they differ is
ⓐ. $3.3 \times 10^5$
ⓑ. $3.3 \times 10^4$
ⓒ. $3.3 \times 10^6$
ⓓ. $3.3 \times 10^8$
Correct Answer: $3.3 \times 10^6$
Explanation: A difference of 0.1% means multiplying the total by 0.001. So $3.3 \times 10^9 \times 0.001 = 3.3 \times 10^6$. This shows that even though humans are overwhelmingly similar genetically, millions of positions can still vary. That remaining variation is enough to support polymorphism studies and DNA-based identification.
511. Which statement correctly describes the protein-coding fraction of the human genome in this chapter treatment?
ⓐ. Nearly the entire genome codes for proteins.
ⓑ. About half of the genome codes for proteins.
ⓒ. Less than 2% of the genome codes for proteins.
ⓓ. Exactly 20% of the genome codes for proteins.
Correct Answer: Less than 2% of the genome codes for proteins.
Explanation: A striking result of human genome analysis is that only a very small fraction of the genome directly codes for proteins. In this chapter treatment, that fraction is given as less than 2%. This means that most of the genome is non-coding, though non-coding does not necessarily mean unimportant. The result challenged simple assumptions that most DNA would be protein-coding.
512. Which Human Genome Project finding most directly argues against the idea that organismal complexity depends simply on protein-coding DNA percentage?
ⓐ. The human genome contains exactly 64 codons.
ⓑ. Less than 2% of the human genome codes for proteins despite the complexity of humans.
ⓒ. Human chromosome Y has fewer genes than chromosome 1.
ⓓ. The genome contains about 3164.7 million base pairs.
Correct Answer: Less than 2% of the human genome codes for proteins despite the complexity of humans.
Explanation: A common naive expectation is that a more complex organism must have most of its genome devoted to coding proteins. Human genome analysis showed otherwise, since less than 2% of the genome codes for proteins here. This means complexity cannot be explained simply by coding percentage alone. The finding pushed biology toward broader views of genome organization and regulation.
513. A large part of the human genome is described here as consisting of
ⓐ. repetitive DNA sequences
ⓑ. only promoter regions
ⓒ. only ribosomal genes
ⓓ. purely protein-coding exons
Correct Answer: repetitive DNA sequences
Explanation: The human genome contains a substantial proportion of repetitive DNA. These repeated sequences make up a large part of the genome even though they do not represent ordinary protein-coding regions. Their abundance is one reason genome organization is more complex than a simple list of genes. Repetitive DNA also becomes important later in the discussion of polymorphism and DNA fingerprinting.
514. Which chromosome is described in this chapter treatment as having the highest number of genes?
ⓐ. chromosome Y
ⓑ. chromosome X
ⓒ. chromosome 21
ⓓ. chromosome 1
Correct Answer: chromosome 1
Explanation: Chromosome 1 is described here as carrying the highest number of genes among human chromosomes. This is one of the chapter’s summary facts from genome analysis. It helps show that genes are not distributed uniformly across all chromosomes. Different chromosomes contribute unequally to the total gene content of the genome.
515. Which chromosome is described here as having the fewest genes?
ⓐ. chromosome 1
ⓑ. chromosome Y
ⓒ. chromosome X
ⓓ. chromosome 22
Correct Answer: chromosome Y
Explanation: The Y chromosome is described here as having the fewest genes. This contrasts with chromosome 1, which is presented as having the most genes. The comparison shows that gene distribution is not uniform across the human genome.
516. Assertion: Human genome analysis showed that sequence information alone did not immediately explain every gene’s function.
Reason: More than 50% of discovered genes in this treatment had functions that were not yet known.
ⓐ. Both Assertion and Reason are true, but Reason does not explain Assertion.
ⓑ. Assertion is true, but Reason is false.
ⓒ. Assertion is false, but Reason is true.
ⓓ. Both Assertion and Reason are true, and Reason correctly explains Assertion.
Correct Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.
Explanation: Determining the DNA sequence of the genome was a major achievement, but sequence reading alone did not automatically reveal the role of every gene. In this chapter treatment, more than 50% of discovered genes are described as having unknown functions. This shows the difference between sequencing and understanding biological meaning. The reason therefore directly explains why genome analysis remained incomplete even after large-scale sequencing.
517. Which statement best reflects one important conclusion from analysis of the human genome?
ⓐ. A very small fraction of the genome codes for proteins, while much of the rest is non-coding.
ⓑ. Nearly the whole genome is made only of coding exons.
ⓒ. All human DNA consists only of structural genes with known functions.
ⓓ. Protein-coding regions occupy more than half of the genome.
Correct Answer: A very small fraction of the genome codes for proteins, while much of the rest is non-coding.
Explanation: Human genome analysis showed that protein-coding DNA forms only a small part of the total genome. In this chapter treatment, less than 2% of the genome is said to code for proteins. This means that most human DNA is non-coding, including repetitive and other sequences. The result changed the simple expectation that most DNA would directly code for proteins.
518. About how many SNP locations are noted in this chapter treatment for the human genome?
ⓐ. about 14,000
ⓑ. about 1,400
ⓒ. about 1.4 million
ⓓ. about 140 million
Correct Answer: about 1.4 million
Explanation: Single nucleotide polymorphisms, or SNPs, are important points of sequence variation in the human genome. In this chapter treatment, about 1.4 million SNP locations are noted. These sites are valuable for studying human variation, inheritance, and mapping of genes. Their large number also shows that small sequence differences are spread widely across the genome.
519. Which statement is most consistent with the finding that about 99.9% of human nucleotide bases are the same?
ⓐ. Humans show no genetic differences at all.
ⓑ. Every visible human difference must come from protein-coding genes alone.
ⓒ. Human genomes are identical in every position.
ⓓ. A relatively small fraction of genomic variation can still account for individual differences.
Correct Answer: A relatively small fraction of genomic variation can still account for individual differences.
Explanation: Even though humans are about 99.9% similar at the nucleotide level, the remaining small proportion of variation is still biologically important. That limited variation contributes to differences among individuals and is useful in genetic identification. The finding therefore shows both similarity and individuality at the same time. Small genomic differences can have meaningful effects.
520. Which comparison is correct according to this chapter treatment?
ⓐ. Chromosome Y has the most genes, while chromosome 1 has the fewest.
ⓑ. Chromosome 1 has the most genes, while chromosome Y has the fewest.
ⓒ. Both chromosome 1 and chromosome Y have nearly equal gene numbers.
ⓓ. Chromosome X has the most genes, while chromosome 21 has the fewest.
Correct Answer: Chromosome 1 has the most genes, while chromosome Y has the fewest.
Explanation: Human chromosomes do not all carry the same number of genes. In this chapter treatment, chromosome 1 is described as having the highest number of genes, whereas chromosome Y has the fewest. This uneven distribution is one of the notable findings from genome analysis. It also reminds us that chromosomes differ in more than just size.
