Chapter 13

Approximately what percentage of the human genome actually codes for proteins? 99.0% 2.5% 97.5% 1.0% 45.0%

2.5%

How many pairs of chromosomes does the human genome normally have? 15 23 6 46 38

23

The human genome has 23 distinct types of chromosomes. How many individual DNA molecules would be present in the nucleus of a human skin cell just before mitosis? 46 92 roughly 23,000 69 23

92 Students are told that humans have 23 chromosome and need to remember that they are diploid and that each of the copies (46 in each diploid cell in G1 phase) replicate before cell division. Some students may remember that the human genome contains about 23,000 genes, but genes and chromosomes are not in a one-to-one relationship.

Sequences of genomic DNA, and its corresponding messenger RNA (mRNA), are often compared to obtain valuable information for genome annotation. Why is this comparison useful? The genomic DNA is longer because the exons are spliced together. The open reading frame of the mRNA includes the introns of the genomic DNA. The genomic DNA is shorter because the exons are spliced together. The sequences of genomic DNA and mRNA are identical, which serves as independent validation. The exclusion of introns in mRNA reveals the intron-exon structure of many protein coding genes.

The exclusion of introns in mRNA reveals the intron-exon structure of many protein coding genes.

Which one of the following BEST describes why genome sequencing can be complicated by repeated sequences? Repeated sequences artificially inflate the genome size, leading to an exaggerated interpretation of the complexity of the organism. Automated sequencing devices interpret repeated sequences as a single-copy sequence. The repeated sequences are often longer than the sequences obtained by automated sequencing. All of these choices are correct. The repeated sequences are too small to gather usable sequence information from.

The repeated sequences are often longer than the sequences obtained by automated sequencing.

Sometimes a single-stranded molecule of RNA is able to fold back on itself because the nucleotide sequence on one part of the RNA is complementary to another part. This sequence motif results in a: positive supercoil. transcription factor binding site. chromosome scaffold. negative supercoil. hairpin-shaped structure.

hairpin-shaped structure.

Which one of the following is NOT found in a bacterial nucleoid? enzymes histones supercoiled DNA All of these choices are correct. proteins

histones

Polyploidy, which is widespread among plants, can arise from which of the following processes? (Select all that apply.) hybridization between related species followed by duplication expansion of regions of highly repetitive DNA deletion of long stretches of noncoding DNA over time duplication of a complete set of chromosomes in a single species introduction of DNA from one species into another via insects and birds

hybridization between related species followed by duplication duplication of a complete set of chromosomes in a single species