Exam 5: DNA and Chromosomes

For a better understanding of DNA structure, it helps to be able to compare physical characteristics evident from a side view of double-stranded DNA with those of individual base pairs. A.Use brackets to designate the major and minor grooves on Figure 5-68A and shade in the surface that will be exposed in the major groove in Figure 5-68B. B.If base pairs were aligned and stacked directly on top of each other, the major and minor grooves would be linear depressions all along the DNA.Explain why this is not the actual conformation of a DNA molecule. (A) (B) Figure 5-68

Which of the following chemical groups is NOT used to construct a DNA molecule?

In principle, what is the minimum number of nucleotides necessary to code for each amino acid? Keep in mind there are twenty different naturally-occurring amino acids, and that each amino acid is encoded by the same number of nucleotides.

Because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds.Every unique DNA molecule "melts" at a different temperature.In this context, T_m (melting temperature) is the point at which two strands separate, or become denatured.Order the DNA sequences listed below according to relative melting temperatures (from lowest T_m to highest T_m).Assume that they all begin as stable double-stranded DNA molecules.Explain your answer. A.GGCGCACC B.TATTGTCT C.GACTCCTG D.CTAACTGG

Which of the following structural characteristics is NOT normally observed in a DNA duplex?

In the 1940s, proteins were thought to be the more likely molecules to house genetic information.What was the primary reason that DNA was not originally believed to be the genetic material?

Which of the following questions would NOT be answered by using karyotyping?

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule.Chromatin-remodeling complexes provide this access by

Several experiments were required to demonstrate how traits are inherited.Which scientist or team of scientists first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently cause changes in the new cells?

The relationship between the nucleic acid sequence over a stretch of DNA and the order of amino acids in the resulting protein is referred to as the __________ code.

DNA is an information storage molecule, whose sequences serve as a template to make

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once. 10,000 chromosome mitosis 100 different nuclear envelope 1000 DNA nucleolus cell cycle dynamic proteins cell wall interphase similar chromatin lipids static Each chromosome is a single molecule of __________ whose extraordinarily long length can be compacted by as much as __________-fold during __________ and tenfold more during __________.This is accomplished by binding to __________ that help package the DNA in an orderly manner so it can fit in the small space delimited by the __________.The structure of the DNA-protein complex, called __________, is highly __________ over time.

The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner.Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle.Which of the following histone proteins does NOT form part of the octameric core?

The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body.Answer the quantitative questions below by choosing one of the numbers in the following list: 23 69 >200 46 92 >10⁹ A.How many centromeres are in each cell? What is the main function of the centromere? B.How many telomeres are in each cell? What is their main function? C.How many replication origins are in each cell? What is their main function?

Given the sequence of one strand of a DNA helix (below), provide the sequence of the complementary strand and label the 5′ and 3′ ends. 5′-GCATTCGTGGGTAG-3′

Describe the mechanism by which heterochromatin can spread, once it has been established in one region of the chromosome.

The structures of the four bases in DNA are given in Figure 5-42. Figure 5-42 A.Which are purines and which are pyrimidines? B.Which bases pair with each other in double-stranded DNA?

The DNA from two different species can often be distinguished by a difference in the

For each of the following sentences, choose one of the options enclosed in square brackets to make a correct statement about nucleosomes. A.Nucleosomes are present in [prokaryotic/eukaryotic] chromosomes, but not in [prokaryotic/eukaryotic] chromosomes. B.A nucleosome contains two molecules each of histones [H1 and H2A/H2A and H2B] as well as of histones H3 and H4. C.A nucleosome core particle contains a core of histone with DNA wrapped around it approximately [twice/three times/four times]. D.Nucleosomes are aided in their formation by the high proportion of [acidic/basic/polar] amino acids in histone proteins. E.Nucleosome formation compacts the DNA into approximately [one-third/one-hundredth/one-thousandth] of its original length.