Genetics Ch 2 exam review

Short-answer: One of the strands in a DNA double helix has the nucleotide sequence 5'-ACCTGCTACGG-3'. What is the sequence of the complementary DNA strand?

3'-TGGACGATGCC-5'

Short-answer: What are the three necessary characteristics of the hereditary molecule in cells?

(1) It must be able to carry information, (2) it must be able to accurately pass on the information to progeny cells (replicate), and (3) it must be capable of change (evolution).

Short-answer: Describe the packing of chromatin from the 10-nm to the 30-nm fiber stage. What is the role of histones?

10-nm chromatin fiber consists of nucleosomes-ʺbeadsʺ of DNA wound around eight core histone proteins-connected by strands of linker DNA. The 30-nm chromatin fiber is created by the binding of histone H1, which brings the linker DNA and the nucleosomes closer together. In the solenoid model of the 30-nm fiber, the nucleosomes are brought together into a spiraling helical structure, with about six nucleosomes per complete turn.

Short-answer: Name the constituent parts of a nucleoside and a nucleotide.

A nucleoside consists of a pentose sugar covalently bonded to a nitrogenous base, a nucleotide is a nucleoside with the addition of a phosphate group.

What did the X-ray diffraction patterns initially reveal about the DNA molecule? A) It is of uniform diameter and has a helical structure. B) It is a helical molecule with paired bases in the center. C) It is double-stranded with antiparallel strands. D) It is acidic phosphorus-rich, and large. E) It contains hereditary information.

A) It is of uniform diameter and has a helical structure.

Nucleoid A) The region of a prokaryotic cell where the chromosome is located B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology C) A DNA molecule and associated proteins D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers E) The constituent monomer of DNA and RNA

A) The region of a prokaryotic cell where the chromosome is located

The C-value is the amount of DNA in a A) haploid genome. B) diploid genome. C) bacterial genome. D) eukaryotic genome.

A) haploid genome.

Antiparallel means that A) the two polynucleotide chains run in opposite directions. B) each DNA molecule consists of one old and one new strand. C) opposite strands are held together by base pairing. D) the helix twists to the right. E) there is complementary base-pairing

A) the two polynucleotide chains run in opposite directions.

Which of the following is a nonhistone protein found in chromatin? A) H1 B) HMG C) H2A D) H5 E) All of these

B) HMG

Who used radioactively labeled T2 bacteriophage to confirm the identity of the transforming principle? A) Griffith B) Hershey and Chase C) Avery D) Gierer and Schramm E) Beadle and Tatum

B) Hershey and Chase

What did Watson and Crick deduce about the three-dimensional structure of DNA? A) There is a repeating pattern every 3.4 nm and every 0.34 nm. B) It is a double-stranded helix. C) It contains a lot of phosphorus. D) It is a large molecule. E) It consists of supercoiled chromatin.

B) It is a double-stranded helix.

Which part of the T2 bacteriophage entered E. coli cells in the experiment which confirmed the identity of the transforming principle? A) The RNA B) The DNA C) The whole virus D) The protein coat E) No part

B) The DNA

Nucleosome A) The region of a prokaryotic cell where the chromosome is located B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology C) A DNA molecule and associated proteins D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers E) The constituent monomer of DNA and RNA

B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology

Loosely aggregated DNA bound to proteins in a eukaryotic cell is called A) chromosomes. B) chromatin. C) chromatid. D) centromere. E) nucleoid.

B) chromatin

The displacement loop (D-loop) may be a characteristic of A) centromeres. B) telomeres. C) A-DNA. D) B-DNA. E) Z-DNA.

B) telomeres.

In Griffithʹs experiment involving the transformation of Streptococcus pneumoniae, A) the R strain was virulent. B) the S strain was virulent. C) both the R and S strains were virulent. D) the R strain had a protein capsule. E) the S strain had a protein capsule.

B) the S strain was virulent.

The chromosome of most prokaryotes differs from those of eukaryotes in that A) the prokaryotic chromosome is linear, while the eukaryotic chromosome is circular. B) the prokaryotic chromosome is circular, while the eukaryotic chromosome is linear. C) the prokaryotic chromosome does not replicate before mitosis, while the eukaryotic chromosome does. D) the prokaryotic chromosome does not contain genes, while the eukaryotic chromosome does. E) the prokaryotic chromosome is not necessary for the organismʹs survival, while the eukaryotic chromosome is.

B) the prokaryotic chromosome is circular, while the eukaryotic chromosome is linear.

Certain ________ have RNA for their genetic material. A) bacteria B) viruses C) plants D) eukaryotes E) prokaryotes

B) viruses

Chromosome A) The region of a prokaryotic cell where the chromosome is located B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology C) A DNA molecule and associated proteins D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers E) The constituent monomer of DNA and RNA

C) A DNA molecule and associated proteins

What was the transforming principle isolated in Griffithʹs experiment? A) Protein B) RNA C) DNA D) Virus E) Polysaccharide

C) DNA

Complementary base-pairing allows for A) spontaneous mutations to occur. B) genes to be expressed as a phenotype. C) DNA to serve as its own template for replication. D) replication to be semiconservative. E) covalent bonds to form between the opposite bases.

C) DNA to serve as its own template for replication.

A Barr body is an example of A) constitutive euchromatin. B) facultative euchromatin. C) facultative heterochromatin. D) a nucleosome.

C) facultative heterochromatin.

Topoisomerases function to A) remove nucleotides from DNA. B) join DNA pieces together. C) twist DNA molecules. D) attach DNA loops to scaffold proteins. E) move chromosomes along spindle fibers.

C) twist DNA molecules.

Short-answer: What is the role of centromeres and telomeres?

Centromeres are the chromosomal regions where mitotic or meiotic spindle fibers attach. They are therefore responsible for the accurate segregation of chromosomes to daughter cells during replication. Telomeres are heterochromatic regions of chromosomes that are also required for replication and stability. They are usually found at the ends of the chromosome and are associated with the nuclear envelope.

Short-answer: Define Chargaffʹs rules of the base composition of DNA.

Chargaffʹs rules include the following: (1) the amount of adenine = the amount of thymine, (2) the amount of guanine = the amount of cytosine, and (3) the amount of purines = the amount of pyrimidines.

The definition of transformation is A) the shift of genetic information from DNA to protein. B) the genetic alteration of an organism. C) the uptake of genetic information by a cell from the environment. D) Both B and C E) None of these E) constitutive heterochromatin.

D) Both B and C

Which of the following are the purine nucleotides in DNA? A) Adenine and thymine B) Cytosine and guanine C) Adenine and cytosine D) Guanine and adenine E) Thymine and uracil

D) Guanine and adenine

Centromere A) The region of a prokaryotic cell where the chromosome is located B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology C) A DNA molecule and associated proteins D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers E) The constituent monomer of DNA and RNA

D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers.

Nucleotide A) The region of a prokaryotic cell where the chromosome is located B) The basic structural unit of chromatin with ʺbead-on-a-stringʺ morphology C) A DNA molecule and associated proteins D) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers E) The constituent monomer of DNA and RNA

E) The constituent monomer of DNA and RNA

25) Which nucleotide is absent in RNA? A) Adenine B) Guanine C) Uracil D) Cytosine E) Thymine

E) Thymine

Which form of DNA is a left-handed double helix? A) A-DNA B) B-DNA C) L-DNA D) R-DNA E) Z-DNA

E) Z-DNA

Short-answer: Describe the differences between heterochromatin and euchromatin in chromosomes. Are there any situations in which one can be changed into the other?

Euchromatin contains actively transcribed genes and undergoes normal cycles of condensation and decondensation in the cell cycle. Heterochromatin remains condensed and contains genes that are usually transcriptionally inactive. Euchromatin can be inactivated, as in the case of Barr bodies. It is then known as facultative heterochromatin.

Short-answer: Why are the amino acid sequences of eukaryotic histones so similar to one another, even among distantly related species?

Evolutionary conservation of these sequences is a strong indicator that histones perform the same basic role in organizing the DNA in the chromosomes of all eukaryotes.

T/F: By weight the amount of DNA in chromatin is less than that of histone.

FALSE

T/F: DNA and RNA both contain phosphate and ribose.

FALSE

T/F: Hershey and Chase used radioactive sulfur to label the genetic material of bacteriophages.

FALSE

T/F: In a strand of DNA, a hydrogen bond connects the phosphate group of one nucleotide to the sugar of the adjacent nucleotide.

FALSE

T/F: The genome of most prokaryotes consists of moderately repetitive DNA.

FALSE

T/F: The genome of the T-even family of bacteriophage consists of single-stranded RNA.

FALSE

T/F: The more condensed a part of a chromosome is, the more likely it is that the genes in that region will be active.

FALSE

Short-answer: If the human egg has 3 billion base pairs, how many nucleosomes will be present in the nucleus of a human somatic cell?

In humans, the DNA wrapped around each nucleosome is approximately 200 bp (147 bp + 53 bp linker). As such, there will be approximately 3 × 109/2 × 102 = 1.5 × 107 nucleosomes in a human egg nucleus. However, the egg is haploid, whereas the somatic cells are diploid. Therefore, there will be approximately 1.5 × 107 × 2 = 3 × 107 nucleosomes in the nucleus of a human somatic cell.

Short-answer: What is the function of dispersed repeated sequences such as SINEs and LINEs in eukaryotes?

Little is known about the function of such sequences, but one hypothesis is that they have no function at all. Another is that they are involved in regulating gene expression.

T/F: Borrelia burgdorferi is a bacterium whose genome consists of one large and several small linear chromosomes.

TRUE

T/F: In eukaryotes, the greatest relative amount of tandemly repeated DNA is associated with centromeres and telomeres.

TRUE

T/F: The virus first shown to have RNA as its genetic material was tobacco mosaic virus (TMV).

TRUE

Short-answer: The DNA phage ΦΧ174 was found to have a ratio of bases of 25A:33T:24G:18C. This departs from the usual A/T = 1 and G/C = 1 ratios. How can you explain this?

The genome of the phage consists of single-stranded, rather than double-stranded: DNA.

Short-answer: In Griffithsʹ transformation experiments, under what conditions did the injected mice die?

The mice died when they were injected with living, virulent bacteria, and when they were injected with living, nonvirulent bacteria mixed with heat-killed, virulent bacteria.

Short-answer: If the base pairs in a DNA helix are 0.34 nm apart, and a complete (360°) turn of the helix takes 3.4 nm. How many base pairs per turn are there in a DNA molecule?

There are 10 base pairs per turn.

Short-answer: What is the C-value paradox and what is its cause?

There is also no direct relationship between the C-value (the total amount of DNA in the haploid genome) and the structural or organizational complexity of the organism. This is due in part to the amount of repetitive-sequence DNA found in the genome of some organisms.

Short-answer: How could you test whether the transforming ability of a cell extract was due to DNA or RNA?

You could treat the extract with a DNase or RNase enzyme and test whether its transforming ability was intact.