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Biology Ch. 13

Terms in this set (39)

In terms of the sequence known as "the human genome," which statement is true?
It does not really exist in any human being.
Which step comes first in shotgun sequencing?
breaking the DNA into small fragments
One difference between eukaryotic and prokaryotic DNA packaging is that:
DNA wraps around histones in eukaryotes
Which statement is true about the chromatin packaging in eukaryotes?
Histone proteins are positively charged, which allows them to bind to and pack negatively charged DNA.
If you want to identify protein-coding DNA sequences, why is it more efficient to study messenger RNAs than DNA?
because processed mRNA does not contain introns
A virus with a wide host range may infect multiple species of both animals and plants:
false
Bacterial nucleoid does not contain:
histones
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?
92
The complexity of an organism is proportional to the number of genes in its genome.
false
Sequences of genomic DNA and the corresponding messenger RNA (mRNA) are often compared to obtain valuable information for genome annotation. Why is this comparison useful?
The exclusion of introns in mRNA reveals the intron-exon structure of many protein coding genes.
Chloroplasts and mitochondrion have double-stranded RNA genomes.
false
Which is a feature of DNA that could allow you to distinguish between a DNA sequence that is protein coding and a DNA sequence that is not?
Protein-coding DNA sequences frequently contain long open reading frames; nonprotein-coding DNA sequences rarely do.
Which characteristic is true of all viruses? Select all that apply.
They must infect a host cell to reproduce.
A genetic engineer wants to modify a virus to insert a synthetic gene into human lung cells. Which modified viruses would achieve her goal?
a rabies virus modified to infect lung cells and carry the gene
In using the shotgun approach to genome sequencing, the sequenced fragments originate from:
random sites scattered across the genome.
Polyploids with an odd number of sets of chromosomes have many problems in meiosis but none in mitosis. Why?
Homologous chromosomes pair in meiosis.
Repeated DNA sequences represent a special challenge in genome sequence assembly. Which would be harder to assemble correctly, assuming the number of copies of the repeat can be determined?
sequences containing repeats longer than the DNA fragments to assemble
Some viruses with an RNA genome require a virus-encoded reverse transcriptase.
true
The genome of a newly identified organism is discovered and genome assembly shows that it is a single continuous strand of DNA. This organism is more likely to be:
a bacterium.
Organisms that have bigger genomes are more complex than organisms with smaller genomes?
false
The vast majority of naturally occurring polyploids have an even number of sets of chromosomes.
true
When an open reading frame (ORF) is identified, it may not actually correspond to the amino acid sequence of any polypeptide in the cell.
true
Approximately what percentage of the human genome actually codes for proteins?
2.5%
Human mitochondrial DNA does not have telomeres because it is:
circular
Tandem repeats complicate the alignment of DNA fragments in shotgun sequencing. Which action might solve that problem?
Develop techniques to sequence longer DNA fragments.
Assembling complete genomic sequences based on the overlap of sequenced fragments can be difficult because the sequenced fragments:Select all that apply.
All of these choices are correct
-may have errors in them.
-may come from either DNA strand.
-may overlap but come from different locations in the genome.
-may actually come from bacteria, viruses, or other contaminants.
-may be relatively short (50-100 nucleotides).
Which would be found in DNA sequences but not in mRNA sequences?
transcription start sites
DNA that does not code for proteins serves no function in the cell.
false
A shotgun sequencing project yields a sequence for a strand of DNA.
5′-GGTTTGGAGTAT-3′
In assembling the genome sequence from the short fragments, you look for other fragments that overlap the sequence above. Which sequence overlaps with the given sequence?
5′-TTTGGAGTATGG-3′
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:
hairpin-shaped structure.
Which statement explains why the size of an organism's genome is not directly related to the complexity of the organism?
All of these choices are correct.
-Some genomes have more than two copies of each chromosome.
-Different genomes have different amounts of highly repetitive DNA sequences.
-Different genomes have different amounts of moderately repetitive DNA sequences.
Which pair of people has the exact same genome?
monozygotic twins
The estimated number of genes in the human genome is:
25,000
In eukaryotes, genetic material is packaged in the nucleus. Which group accurately lists the levels of the packaging in order of increasing size?
nucleosome, chromatin, chromosome
Which statement applies to transposable elements?
All of these choices are correct.
-Their numbers can increase from one generation to the next.
-They account for a significant fraction of the human genome.
-some kinds can replicate via an RNA intermediate.
-some can replicate and insert themselves into another place in the genome.
Which statement represents repeated sequences commonly found in the human genome?
All of these choices are correct.
-long sequences dispersed throughout the genome
-short sequences repeated many times in tandem
-sequences whose transcript can fold back to form a hairpin
-ong sequences repeated in tandem
How can researchers distinguish exons from introns in a segment of DNA?
The sequence of exons complements mRNA molecules in the cell.
Which statement about transposable elements is correct?
All of these choices are correct
-They are sometimes described as "selfish" and called "the ultimate parasite."
-They make up 45% of the DNA in the human genome.
-They can transpose via DNA replication or an RNA intermediate.
-They replicate themselves and insert themselves into new positions.
Sequences that are conserved, that is, similar in many different organisms, are unlikely to be functionally important.
false
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