Deck 6: Genes and Genomes

Question 1

The genomes of salamanders contain ten times more DNA than the genomes of humans because salamanders

A) have ten times more genes than humans have.
B) need more DNA so they can regenerate new limbs.
C) have more noncoding DNA than humans have.
D) are more complex than humans.

Answer 1

C

Question 2

A gene can be defined as a segment of DNA that codes for

A) a protein.
B) a functional product.
C) messenger RNA.
D) messenger RNA or ribosomal RNA.

Answer 2

B

Question 3

Introns in mRNA-coding genes are the transcribed sequences

A) that code for proteins.
B) that regulate mRNA translation.
C) that are removed by nucleases.
D) between protein-coding sequences.

Answer 3

D

Question 4

In the nucleus, introns are removed from transcripts by

A) restriction nucleases.
B) splicing.
C) exonucleases.
D) endonucleases.

Question 5

Introns were discovered when mRNA for adenovirus protein expressed in mammalian cells was hybridized to single-stranded virus DNA coding for that mRNA. When the complexes were observed under the electron microscope,

A) a completely double-stranded hybrid was seen.
B) a partial hybrid with loops of mRNA extending from the hybrid regions was seen.
C) a partial hybrid with loops of DNA extending from the hybrid regions was seen.
D) no hybrid was seen, because the introns had been removed.

Question 6

Introns can encode

A) small nucleolar RNAs.
B) microRNAs.
C) sequences that control gene expression.
D) All of the above

Question 7

Introns are found

A) commonly in eukaryotic genes and rarely in prokaryotic genes.
B) only in eukaryotic genes.
C) commonly in both eukaryotic and prokaryotic genes.
D) only in prokaryotic genes.

Question 8

Histone genes have

A) a single long intron.
B) no introns.
C) larger introns than exons.
D) larger exons than introns.

Question 9

Introns constitute about what percentage of the average human gene?

A) 3%
B) 40%
C) 60%
D) 90%

Question 10

A gene family is a

A) set of related but slightly different genes present in one individual.
B) family of individuals with the same gene.
C) set of slightly different genes present as one copy each in a set of individuals.
D) family of individuals in which each has an identical sequence of the same gene.

Question 11

What is the term used to describe functional protein encoding regions found completely within an intron?

A) Pseudogene
B) Polymorphism
C) Nested gene
D) Alternative splicing

Question 12

Synthesis of different proteins from the same gene is due to

A) intron shuffling.
B) exon shuffling.
C) alternative splicing.
D) exon splicing.

Question 13

During the processing of miRNAs, which of the following cleaves the 5ʹ and 3ʹ tails away from the hairpin structure in the primary miRNA transcript?

A) Drosha
B) Dicer
C) RNAse
D) Integrase

Question 14

The consequence of the action of many miRNAs is the blocking or reduction of the eventual expression of proteins. What is the mechanism of action by which miRNAs accomplish this?

A) miRNAs complementary base pair with mRNAs and inhibit translation and stimulate mRNA degradation.
B) miRNAs complementary base pair to regulatory regions of genes and inhibit the transcription of genes.
C) miRNAs complementary base pair to the active site on rRNAs and prevent the mRNA from interacting with ribosomes.
D) miRNAs complementary base pair with intron-exon boundary sequences and prevent correct mRNA processing.

Question 15

Simple-sequence repeats

A) are not transcribed.
B) are present in tandem arrays of thousands of copies.
C) account for approximately 10% of the human genome.
D) All of the above

Question 16

Pseudogenes are

A) genes that code for an RNA but do not code for a protein.
B) nonfunctional gene copies.
C) inactive genes.
D) genes containing variant sequences.

Question 17

Retrotransposons and retroviruses share similar mechanisms by encoding which of the following enzymes?

A) Reverse transcriptase and RNA polymerase
B) Reverse transcriptase and integrase
C) RNA polymerase and integrase
D) DNA polymerase and integrase

Question 18

Most pseudogenes are thought to have originated via

A) duplication of genes that then became nonfunctional through mutation.
B) reverse transcription of an mRNA and integration of the cDNA into a new chromosomal site.
C) genome-wide duplication and the inactivation of one homolog by mutation.
D) fusion of a prokaryotic cell with a eukaryotic cell.

Question 19

Which of the following is the most abundant form of chromatin in the interphase nucleus of a cell?

A) Euchromatin
B) Nucleoli
C) Chromosomes
D) Heterochromatin

Question 20

During metaphase in actively dividing cells, DNA is in

A) heterochromatin.
B) nucleoli.
C) chromosomes.
D) euchromatin.

Question 21

During which phase of mitosis does the nuclear membrane reform?

A) Telophase
B) Metaphase
C) Anaphase
D) Prophase

Question 22

The extended length of all the DNA in one human cell is about two

A) millimeters.
B) centimeters.
C) meters.
D) kilometers.

Question 23

Each human has _______ pairs of chromosomes.

A) 21
B) 22
C) 23
D) 24

Question 24

The chromosomes of prokaryotes differ from those of eukaryotes in that prokaryotic chromosomes are

A) linear.
B) multiple.
C) complexed with histones.
D) circular.

Question 25

The DNA of eukaryotic cells is wrapped around histones to form structures called

A) nucleoli.
B) nuclear matrices.
C) nucleosomes.
D) centromeres.

Question 26

Nuclease digestion of chromatin occurs at sites separated by approximately 200 base pairs because

A) an AT-rich region occurs every 200 base pairs.
B) nucleosomes are spaced 200 base pairs apart.
C) a restriction nuclease site occurs every 200 base pairs.
D) two turns of the DNA around the nucleosome consist of 200 base pairs.

Question 27

Heterochromatin consists of

A) DNA associated with nucleosomes.
B) 10-nm chromatin fibers.
C) decondensed, transcriptionally active chromatin.
D) highly condensed, transcriptionally inactive chromatin.

Question 28

Euchromatin consists of

A) decondensed, transcriptionally active chromatin.
B) 100-nm chromatin fibers.
C) DNA associated with nucleosomes.
D) highly condensed, transcriptionally inactive chromatin.

Question 29

A centromere is a

A) region of euchromatin devoid of histones.
B) sequence at the end of chromatids.
C) region where proteins bind to form kinetochores.
D) specific, repeated DNA sequence.

Question 30

Kinetochores are the

A) sites of spindle fiber attachment to chromosomes.
B) regions where two chromosomes remain attached during mitosis.
C) same as centromeres.
D) structures at the base of cilia and flagella.

Question 31

During mitosis, highly condensed chromosomes consist of two sister chromatids joined at the

A) centrosome.
B) centromere.
C) kinetochore.
D) spindle fiber.

Question 32

The transfer of information from parent to progeny that is not based on DNA sequences is known as

A) epigenetic inheritance.
B) non-Mendelian genetics.
C) sex-linked inheritance.
D) Mendelian genetics.

Question 33

Telomeres are

A) microtubule binding sites in the center of chromosomes.
B) sites at the ends of chromosomes where DNA replication begins.
C) chromosome end structures required for complete replication of linear chromosomes.
D) sites at the ends of chromosomes where microtubules bind.

Question 34

The function of telomeres is to

A) degrade the ends of chromosomes.
B) provide repetitive sequences in circular DNA molecules.
C) join two sister chromatids.
D) provide a site for replication of chromosome ends.

Question 35

Introns are removed by _______.

Question 36

Different proteins may be produced from the same gene through the process of _______.

Question 37

Regulation of gene expression by short double-stranded RNAs is not only an important experimental method but is also normally used by cells to control mRNA _______ and _______.

Question 38

The endogenous noncoding RNAs that mediate RNA interference are _______.

Question 39

SINEs and LINEs are types of _______ DNA sequences.

Question 40

In some breeds of dogs, the premature termination of bone growth results in short legs. In these breeds, the mRNA encoding by the gene responsible for leg length undergoes _______ and gets inserted into a LINE where its expression is impaired.

Question 41

Electron microscopy of chromatin revealed that chromatin has a beaded appearance. The beads were later identified to be _______.

Question 42

Eukaryotic DNA wrapped around a core of eight histones forms a _______.

Question 43

The chromatin that is decondensed and contains most of the active genes is called _______.

Question 44

The chromatin that is highly condensed and contains mostly inactive genes is called _______.

Question 45

Prior to undergoing mitosis, dividing cells replicate DNA during _______.

Question 46

The specialized regions of eukaryotic chromosomes that serve as sites for association with sister chromatids are called _______.

Question 47

The specialized sequences at the ends of eukaryotic chromosomes are called _______.

Question 48

The enzyme that replicates the sequences at the end of eukaryotic chromosomes is called _______.

Question 49

Cancer cells have high levels of the enzyme _______, allowing them to maintain the ends of their chromosome through indefinite divisions.

Question 50

The protein complex that protects the ends of chromosomes is _______.

Question 51

The ENCODE Project revealed that as much as 75% of the human genome is transcribed.

Question 52

Introns are nonfunctional sequences between exons.

Question 53

A single miRNA can target up to 100 different mRNAs.

Question 54

miRNAs often lie within introns of protein-coding genes.

Question 55

The mature miRNA contains a double-stranded RNA incorporated into the RISC complex.

Question 56

During retrotransposition, reverse transcription occurs before integration.

Question 57

Transposable elements have played a major role in stimulating gene rearrangements that have contributed to the generation of genetic diversity.

Question 58

Many of the genetic alterations responsible for inherited diseases may be due to mutations in functional noncoding regions rather than in protein-coding sequences.

Question 59

Partial digestion of eukaryotic chromatin with micrococcal nuclease (an endonuclease) results in DNA fragments that are 200 (or multiples of 200) base pairs long because nucleosomes are spaced 200 base pairs apart.

Question 60

Heterochromatin gets its name from the fact that it contains a mixture of active and inactive genes.

Question 61

Telomeres are required for the complete replication of linear chromosomes.

Question 62

Epigenetic inheritance is the transfer from parent to progeny of information that is not encoded in DNA sequences.

Question 63

A gene containing three exons would have how many introns?

Question 64

How many possible mRNAs could be derived from a gene with three exons (exon 1, exon 2, and exon 3)?

Question 65

What explains how humans are able to express over 85,000 proteins when we are reported to only have about 21,000 genes?

Question 66

Why would a deleterious genetic mutation in a gene on the X chromosome more likely affect males than females?

Question 67

What was the very important outcome of the ENCODE Project?

Question 68

Describe the mechanisms by which retrotransposons such as SINEs and LINEs get moved around within the genome.

Question 69

When chromatin DNA is partially digested with micrococcal nuclease (an enzyme that degrades DNA) and subsequently run on an agarose gel, it is found to yield DNA fragments approximately 200 base pairs long. What is the explanation for this?

Question 70

Give two reasons why a specific telomere structure is required at the end of a eukaryotic chromosome.

Question 71

What is the difference between telomerase in cancer cells and telomerase in normal somatic cells of an adult, and what is the significance of that difference?

Question 72

Even though its complete genome is significantly smaller than that of humans, the flowering plant Arabidopsis thaliana has about _______ genes, which is about the same number as humans have.

A) 4,000
B) 6,000
C) 26,000
D) 100,000

Question 73

Which statement about introns is true?

A) Though they are part of a gene, they are absent from the corresponding mRNA.
B) They are sequences within genes that are not transcribed.
C) They make up only a small fraction of the DNA of a mammalian gene.
D) Prokaryotes do not have introns in their genes.

Question 74

Which statement about exons is false?

A) An exon may contain a 5ʹ untranslated region.
B) An exon may contain sequences for small nucleolar RNAs.
C) An exon may contain a 3ʹ untranslated region.
D) Exons are separated by introns.

Question 75

Which statement about introns in the yeast Saccharomyces cerevisiae is true?

A) S. cerevisiae genes do not contain introns.
B) A small percentage of S. cerevisiae genes contain introns, and these introns are usually located near the beginning of the gene.
C) Most genes in S. cerevisiae contain introns.
D) Few S. cerevisiae genes contain introns, but those that do contain several.

Question 76

The percentage of the average human gene that encodes proteins is approximately

A) 3%.
B) 25%.
C) 70%.
D) 90%.

Question 77

The human genome is distributed among _______ chromosomes.

A) 20
B) 23
C) 30
D) 39

Question 78

If a human gene is found to contain five introns, the mature mRNA encoded by that gene would have how many exons?

A) Four exons
B) Five exons
C) Six exons
D) There could be multiple mRNAs that contain between one and six introns.

Question 79

The human genome contains only 20,000 to 25,000 actual gene sequences, yet the human genome can produce up to 100,000 gene products. Which of the following processes accounts for this difference?

A) Alternative splicing
B) Spacer sequences
C) Satellite DNA
D) Short interspersed elements (SINEs)

Question 80

The ENCODE project revealed that as much as 75% of the genome in humans is actually transcribed into RNA. Most of this is non‒protein-coding RNA. Which of the following include two new classes of noncoding RNA discovered by the ENCODE project?

A) mRNA and tRNA
B) rRNA and snRNA
C) Pre-mRNA and hnRNA
D) MicroRNA and lncRNA