chapter 11

A geneticist isolates mitochondrial DNA from a human, a yeast, and a plant. She places each DNA in a separate test tube, but the labels fall off the tubes and she doesn't know which tube contains which DNA. She analyzes one tube and finds that the DNA in it has about 17,000 bp, contains no introns, and has little noncoding DNA between the genes. This tube most likely contains mitochondrial DNA from

a human

Histone proteins

attach to DNA and form compacted DNA-protein associations

The beginning of anaphase is inhibited by a signal from the _____, where spindle fibers are supposed to attach.

centromeres

One explanation for the decrease in oxidative phosphorylation with age is that

damage to mitochondrial DNA increases with age.

When a solution containing double‑stranded DNA is heated, the hydrogen bonds that hold the two strands can be weakened and eventually broken, separating the strands completely. This process is called

denaturation

When double-stranded DNA in solution is heated, the two polynucleotide strands separate from each other, a process called _____ or melting.

denaturation

True or false: The C value, which indicates the amount of DNA in a haploid genome, always correlates to the complexity of the organism.

false

The largest and most complex mitochondrial genomes come from

flowering plants

DNA renaturation experiments are useful strategies to estimate the

genetic relatedness between two species.

Most of the centromere and telomere structures consist of

heterochromatin

Which of these is NOT true of highly repetitive DNA?

highly repetitive DNA is usually transcribed into RNA

A student discovers a small amount of DNA in a test tube but doesn't know its origin. She finds that it has no associated histone proteins and is circular. This DNA is most likely from which genome?

mitochondrial DNA

Many petite mutants in yeast grow slowly, are deficient in aerobic respiration, and exhibit cytoplasmic inheritance. These mutations usually involve defects in genes located on

mitochondrial DNA

Which statement best describes chromatin associated with actively transcribed genes as compared to chromatin associated with genes which are not being actively transcribed?

more relaxed and more acetylated

When a circular DNA gets underrotated by the action of cellular enzymes, the DNA is said to exhibit

negative supercoiling

A distinct clump of prokaryotic DNA observed via electron microscopy is referred to as a

nucleoid

Which of these is NOT a type of eukaryotic DNA sequence?

plasmid

A multiprotein complex called _____ binds to mammalian telomeres and helps to stabilize the ends of chromosomes.

shelterin

What is the purpose of a telomere?

stabilize the end of a chromosome

Which term describes the tertiary structural organization of chromosomal DNA that allows the long strand to be packed and fit into the cytoplasm of the cell?

supercoiling

The natural ends of chromosomes are called _____, which stabilize the chromosomes and provide a means for replicating the ends of chromosomes.

telomeres

true or false: mtDNA and cpDNA contain rRNA and tRNA genes of their own for their organelle‑specific functions.

true

Renaturation is when

two DNA strands that were once separated anneal back together

When is a t-loop created in a chromosome?

when the single-stranded G-rich overhang binds to a different section of the chromosome

The amount of DNA in one set of chromosomes in an organism is termed its

C-value

DNA is wrapped around histone proteins and coiled to form a dense fiber called chromatin. Which statement describes the function of the chromatin conformation of DNA?

DNA is wrapped around histone proteins to condense and organize DNA

Which of these is generally NOT true about epigenetic effects?

Epigenetic effects are rare and do not affect very many traits.

The eukaryotic protein critical for organizing chromatin structure is histone. Which histone protein is not included in the histone "core" that is often described as the "beads"?

H1

How do interspersed repeated DNA sequences differ from tandemly repeated DNA sequences?

Interspersed repeated DNA is derived from transposable elements, but tandemly repeated DNA is not.

Which statement about cellular DNA in incorrect?

Most cellular DNA is positively supercoiled.

The antibiotics tetracycline and erythromycin inhibit bacterial protein synthesis, but have no effect on proteins encoded by eukaryotic, nuclear genes. Conversely, the antibiotic cycloheximide inhibits protein synthesis of nuclear genes, but has no effect on protein synthesis in bacteria. Select the statement that best describes the effect of a particular antibiotic on protein synthesis.

Tetracycline treatment would inhibit mitochondrial protein synthesis, but not protein synthesis of nuclear genes.

Suppose a chemist develops a new drug that neutralizes the positive charges on the tails of histone proteins. What would be the most likely effect of this new drug on chromatin structure?

The histones and DNA would not be tightly associated.

In hybridization experiments on six species of plants in the genus Vicia, DNA was isolated from each of the six species, denatured by heating, and sheared into small fragments. In one experiment, samples of DNA from each species and from Escherichia coli were allowed to renature. The graph shows the results of this renaturation experiment. Determine the likely reason that E. coli DNA renatures at a faster rate than DNA from all of the Vicia species. Notice that, for the Vicia species, the rate of renaturation is much faster in the first hour and then slows down. Determine the likely cause of this initial rapid renaturation and the subsequent slowdown.

- There are more copies of the smaller E. coli genome than there are of the plant genome for the same amount of DNA. - The repetitive sequences renature faster than single‑copy sequences.

Gunter Korge examined several proteins that are secreted from the salivary glands of Drosophila melanogaster during larval development. One protein, called protein fraction four, was encoded by a gene found by deletion mapping to be located on the X chromosome at position 3C. Korge observed that, about five hours before the first synthesis of protein fraction four, an expanded and puffed‑out region formed on the X chromosome at position 3C. This chromosome puff disappeared before the end of the third larval instar stage, when the synthesis of protein fraction four ceased. He observed that there was no puff at position 3C in a special strain of flies that lacked secretion of protein fraction four. What is the chromosome puff at position 3C? Why does the disappearance of the puff at position 3C roughly coincide with lack of the secretion of protein fraction 4?

- a region of active transcription - the disappearance of the puff region at 3C indicates lack of transcription from the region with the gene for protein fraction 4

Which organelle or organelles contain DNA of their own?

- chloroplasts - mitochondria

Classify each feature as describing euchromatin, heterochromatin, or both.

- euchromatin: is loosely packed, is accessible to transcription machinery, found in prokaryotes, major state of most genes - both: state of DNA organization - heterochromatin: tightly packed, inaccessible to transcription machinery, the major state of the inactive X chromosome

Classify each of the descriptions as a characteristic of mitochondria only, chloroplasts only, or both mitochondria and chloroplasts.

- mitochondria only: perform cellular respiration, contain cristae - chloroplasts only: perform photosynthesis, contain grana - both: contain DNA, produce energy, found in plants

In 1979, bones found outside Ekaterinburg, Russia, were shown to be those of Tsar Nicholas and his family, who were executed in 1918 by a Bolshevik firing squad in the Russian Revolution. To prove that the skeletons were those of the royal family, mtDNA was extracted from the bone samples, amplified by PCR, and compared with mtDNA from living relatives of the tsar's family. Select options indicating why DNA from the mitochondria analyzed instead of nuclear DNA. From which living relatives would mitochondrial DNA provide useful information for verifying that the skeletons were those of the royal family?

- mitochondrial DNA does not undergo recombination, mitochondrial genomes are present in multiple copies in the cells - the mtDNA from the tsar's living relatives of maternal descent should be analyzed

One example of non-Mendelian inheritance is uniparental inheritance. Choose the definition of uniparental inheritance. Select the examples of genetic material that are uniparentally inherited in sexually reproducing eukaryotes.

- one parent transmits all genetic information to all offspring - plastid DNA, mitochondrial DNA

Classify each feature as describing prokaryotic DNA structure or eukaryotic DNA structure.

- prokaryotic DNA structure: DNA is circular, condensed only by DNA supercoiling, occurs as a single looped structure, does not have telomere region - DNA is linear, condensed around histone proteins, occurs as multiple chromosomes, has repeating telomere region

Which of the statements are true of endosymbiotic theory?

- states than ancestral eukaryotic cell engulfed a photosynthetic protobacteria - explains the origin of some eukaryotic organelles, such as mitochondria - explains why chloroplasts contain their own genetic information

Which statements about euchromatin and heterochromatin are correct?

- the majority of transcription takes place in euchromatin - euchromatic undergoes condensation and decondensation throughout the cell cycle

Eukaryotic DNA consists of

- unique sequences of DNA - highly repetitive DNA sequences - moderately repetitive DNA sequences