Question: Let’s suppose you have recently identified

> Single-strand binding proteins keep the two parental strands of DNA separated from each other until DNA polymerase has an opportunity to replicate the strands. Suggest how single-strand binding proteins keep the strands separated and yet do not impede th

> A short genetic sequence, which may be recognized by primase, is repeated many times throughout the E. coli chromosome. Researchers have hypothesized that primase may recognize this sequence as a site to begin the synthesis of an RNA primer for DNA repli

> Sometimes DNA polymerase makes a mistake, and the wrong nucleotide is added to the growing DNA strand. With regard to pyrimidines and purines, two general types of mistakes are possible. The addition of an incorrect pyrimidine instead of the correct pyri

> Obtain two strings of different colors (e.g., black and white) that are the same length. A length of 20 inches is sufficient. Tie a knot at one end of the black string and another knot at one end of the white string. Each knot designates the 5â&#12

> As shown in Figure 11.5, five DnaA boxes are found within the origin of replication in E. coli. Take a look at these five sequences carefully. A. Are the sequences of the five DnaA boxes very similar to each other? (Hint: Remember that DNA is double-str

> What key structural features of the DNA molecule underlie its ability to be faithfully replicated?

> On rare occasions, a chromosome can suffer a small deletion that removes the centromere. When this occurs, the chromosome usually is not found within subsequent daughter cells. Explain why a chromosome without a centromere is not transmitted very efficie

> How are two topoisomers different from each other? How are they the same?

> In this experiment, which plant, the white- or purple flowered one, is providing the egg cells, and which is providing the sperm cells.

> Describe the role of DNA in the synthesis of a polypeptide.

> Try to explain the function of DNA gyrase with a drawing.

> Take two pieces of string that are approximately 10 inches long, and create a double helix by wrapping them around each other to make 10 complete turns. Tape one end of the strings to a table, and now twist the strings three times (360° each time) in a r

> Coumarins and quinolones are two classes of drugs that inhibit bacterial growth by directly inhibiting DNA gyrase. Discuss two reasons why inhibiting DNA gyrase also inhibits bacterial growth.

> Why is DNA supercoiling called supercoiling rather than just coiling? Why is positive supercoiling called overwinding and negative supercoiling called underwinding? How would you define the terms positive and negative supercoiling for Z DNA (described in

> Describe the mechanisms by which bacterial DNA becomes compacted

> What chemical group (phosphate group, hydroxyl group, or a nitrogenous base) is found at the 3′ end of a DNA strand? What group is found at the 5′ end?

> As the minor and major grooves wind around a DNA double helix, do they ever intersect each other, or do they always run parallel to each other?

> A double-stranded DNA molecule contains 560 nucleotides. How many complete turns occur in this double helix?

> In what ways are the structures of an α helix in a protein and the double helix of DNA similar, and in what ways are they different?

> What is an SMC complex? Describe two examples.

> Which types of macromolecules are found in chromosomes?

> Discuss the differences between the compaction levels of metaphase chromosomes and those of interphase chromosomes. When would you expect gene transcription and DNA replication to take place, during M phase or interphase? Explain why.

> Which of the following terms should not be used to describe a Barr body? A. Chromatin B. Euchromatin C. Heterochromatin D. Chromosome E. Genome

> A typical eukaryotic chromosome found in humans contains about 100 million bp. As noted in Chapter 9, one DNA base pair has a linear length of 0.34 nm. A. What is the linear length of the DNA in a typical human chromosome in micrometers? B. What is the

> What are the roles of the core histone proteins and of histone H1 in the compaction of eukaryotic DNA?

> In Part II of this text, we considered inheritance patterns for diploid eukaryotic species. Bacteria frequently contain two or more nucleoids. With regard to genes and alleles, how is a bacterium that contains two nucleoids similar to a diploid eukaryoti

> In Figure 10.12, what are we looking at in part (b)? Is this an 11-nm fiber, a 30-nm fiber, or a 300-nm fiber? Does this DNA come from a cell during M phase or interphase? From Figure 10.12b: 0.5 pm

> Let’s assume the linker region of DNA averages 54 bp in length. How many molecules of H2A would you expect to find in a DNA sample that is 46,000 bp in length?

> What types of genetic activities occur during interphase? Explain why these activities cannot occur during M phase.

> Compare the structure and cell localization of chromosomes during interphase and M phase

> Compare heterochromatin and euchromatin. What are the differences between them?

> Is DNA a small molecule, a macromolecule, or an organelle?

> Draw a picture depicting the binding between the nuclear matrix and a MAR.

> Beginning with the G1 phase of the cell cycle, describe the level of compaction of the eukaryotic chromosome. How does the level of compaction change as the cell progresses through the cell cycle? Why is it necessary to further compact the chromatin duri

> Describe the structures of a nucleosome and a 30-nm fiber

> Describe the characteristics of highly repetitive DNA sequences.

> What is the function of a centromere? At what stage of the cell cycle would you expect the centromere to be the most important?

> What is a bacterial nucleoid? With regard to cellular membranes, what is the difference between a bacterial nucleoid and a eukaryotic nucleus?

> What is meant by the term DNA sequence?

> If one DNA strand is 5′–GGCATTACACTAGGCCT–3′, what is the sequence of the complementary strand?

> Describe how bases interact with each other in the double helix. This description should include the concepts of complementarity, hydrogen bonding, and base stacking.

> Draw the structure of a phosphodiester linkage.

> Why is it useful to sort male mosquitoes from females?

> Draw the structures of guanine, guanosine, and deoxyguanosine triphosphate

> What are the building blocks of a nucleotide? With regard to the 5′ and 3′ positions on a sugar molecule, how are nucleotides linked together to form a strand of DNA?

> Look up the meaning of the word transformation in a dictionary and explain whether it is an appropriate word to describe the transfer of genetic material from one organism to another.

> Within a protein, certain amino acids are positively charged (e.g., lysine and arginine), some are negatively charged (e.g., glutamate and aspartate), some are polar but uncharged, and some are nonpolar. If you knew that a DNA-binding protein was recogni

> A DNA-binding protein recognizes the following double-stranded sequence: 5′–GCCCGGGC–3′ 3′–CGGGCCCG–5′ This type of double-stranded structure could also occur within the stem region of an RNA stem-loop. Discuss the structural differences between RNA and

> On further analysis of the DNA described in conceptual question C21, you discover that the triplex DNA in this alien organism is composed of a double helix with a third strand wound within the major groove (just like the DNA in Figure 9.15). How would yo

> An organism has a G + C content of 64% in its DNA. What are the percentages of A, T, G, and C?

> After the DNA from type S bacteria is exposed to type R bacteria, list all of the steps that you think must occur for the type R bacteria to start making a capsule.

> Discuss the structural significance of complementarity in DNA and in RNA.

> What ethical issues may be associated with human cloning?

> What structural feature allows DNA to store information?

> Which of the following DNA double helices would be more difficult to separate into single-stranded molecules by treatment with heat, which breaks hydrogen bonds? A. GGCGTACCAGCGCAT CCGCATGGTCGCGTA B. ATACGATTTACGAGA TATGCTAAATGCTCT Explain your choi

> Compare the structural features of a double-stranded RNA structure with those of a DNA double helix.

> Write a sequence of an RNA molecule that could form a stem-loop with 24 nucleotides in the stem and 16 nucleotides in the loop.

> Draw the structure of deoxyribose and number the carbon atoms. Describe the numbering of the carbon atoms in deoxyribose with regard to the directionality of a DNA strand. In a DNA double helix, what does the term antiparallel mean?

> List the structural differences between DNA and RNA.

> What part(s) of a nucleotide (namely, phosphate, sugar, and/or base) is(are) found in the major and minor grooves of doublestranded DNA, and what part(s) is(are) found in the DNA backbone? If a DNA-binding protein does not recognize a specific nucleotide

> Discuss the differences in the structural features of B DNA and Z DNA.

> Make a side-by-side drawing of two DNA helices: one with 10 bp per 360° turn and the other with 15 bp per 360° turn.

> What is the meaning of the term genetic material?

> How might a better understanding of our genes be used in the field of medicine?

> Explain why inversions and reciprocal translocations do not usually cause a phenotypic effect. In a few cases, however, they do. Explain how.

> An inversion heterozygote has the following inverted chromosome: What would be the products if a crossover occurred between genes H and I on the inverted chromosome and a normal chromosome? Centromere A B CD JI HGF E, KL M Inverted region

> An inversion heterozygote has the following inverted chromosome: What would be the products if a crossover occurred between genes H and I on the inverted chromosome and a normal chromosome? Centromere A BJI HGF ED CKLM Inverted region

> Two chromosomes have the following orders for their genes: Normal: A B C centromere D E F G H I Abnormal: A B G F E D centromere C H I Does the abnormal chromosome have a pericentric or a paracentric inversion? Draw a sketch showing how these two chro

> Following a gene duplication, two genes will accumulate different mutations, causing them to have slightly different sequences. In Figure 8.7, which pair of genes would you expect to have more similar sequences, α1 and α2 or &

> What is a gene family? How are gene families produced over time? With regard to gene function, what is the biological significance of a gene family?

> A triploid plant has 18 chromosomes (i.e., 6 chromosomes per set). If we assume a gamete has an equal probability of receiving one or two copies of each of the six types of chromosome, what are the odds of this plant producing a haploid or a diploid game

> The karyotype of a young girl who is affected with familial Down syndrome revealed a total of 46 chromosomes. Her older brother, however, who is phenotypically unaffected, actually had 45 chromosomes. Explain how this could happen. What would you expect

> The kidney bean plant, Phaseolus vulgaris, is a diploid species containing a total of 22 chromosomes in somatic cells. How many possible types of trisomic individuals could be produced in this species?

> Which of the following terms should not be used to describe a human with three copies of chromosome 12? A. Polyploid B. Triploid C. Aneuploid D. Euploid E. 2n + 1 F. Trisomy 12

> Can you think of another example of a model organism?

> A diploid fruit fly has eight chromosomes. Which of the following terms should not be used to describe a fruit fly with four sets of chromosomes? A. Polyploid B. Aneuploid C. Euploid D. Tetraploid E. 4n

> While conducting field studies on a chain of islands, you decide to karyotype two phenotypically identical groups of turtles, which are found on different islands. The turtles on one island have 24 chromosomes, but those on another island have 48 chromos

> How does a chromosomal duplication occur?

> Describe some of the advantages of polyploid plants. What are the consequences of having an odd number of chromosome sets?

> Explain how polytene chromosomes of Drosophila are produced and how they form a six-armed structure.

> What is mosaicism? How is it produced?

> What is endopolyploidy? What is its biological significance?

> A zookeeper has collected a male and a female lizard that look like they belong to the same species. They mate with each other and produce phenotypically normal offspring. However, the offspring are sterile. Suggest one or more explanations for their ste

> Why do you think that humans with trisomy chromosome 13, 18, or 21 can survive but other trisomies are lethal? Even though X chromosomes are large, aneuploidy of this chromosome is also tolerated. Explain why.

> A cytogeneticist has collected tissue samples from members of a certain butterfly species. Some of the butterflies were located in Canada, and others were found in Mexico. Through karyotyping, the cytogeneticist discovered that chromosome 5 of the Canadi

> According to the theory of evolution, why have these changes occurred in horse populations over the course of many generations? From Figure 1.11: Equus Hippidium and other genera Nannippus Stylahipparion 5- Plohippus Hipparion Neohipparion 10- Sinoh

> Female fruit flies homozygous for the X-linked white-eye allele are crossed to males with red eyes. On very rare occasions, an offspring of such a cross is a male with red eyes. Assuming these rare offspring are not due to a new mutation in one of the mo

> Explain how aneuploidy, deletions, and duplications cause genetic imbalances. Why do you think that deletions and monosomies are more detrimental than duplications and trisomies?

> Aneuploidy is typically detrimental, whereas polyploidy is sometimes beneficial, particularly in plants. Discuss why you think this is the case.

> Explain why small deletions and duplications are less likely to have a detrimental effect on an individual’s phenotype than large ones. If a small deletion within a single chromosome happens to have a phenotypic effect, what would you conclude about the

> Two phenotypically unaffected parents produce two children with familial Down syndrome. With regard to chromosomes 14 and 21, what are the chromosomal compositions of the parents?

> A person is born with one X chromosome, zero Y chromosomes, trisomy 21, and two copies of the other chromosomes. How many chromosomes does this person have altogether? Explain whether this person is euploid or aneuploid.

> A diploid fruit fly has eight chromosomes. How many total chromosomes would be found in the following flies? A. Tetraploid B. Trisomy 2 C. Monosomy 3 D. 3n E. 4n + 1

> A phenotypically abnormal individual has a phenotypically normal father with an inversion on one copy of chromosome 7 and a phenotypically normal mother without any changes in chromosome structure. The orders of genes along the two copies of chromosome 7

> Explain why a translocation cross occurs during metaphase of meiosis I when a cell contains a reciprocal translocation.

> Which of the following types of chromosomal changes would you expect to have phenotypic consequences? Explain your choices. A. Pericentric inversion B. Reciprocal translocation C. Deletion D. Unbalanced translocation

> The leaf cells of a corn plant contain 20 chromosomes each. How many chromosomes are found in a gamete made by a corn plant?

> With regard to the segregation of centromeres, why is adjacent-2 segregation less frequent than alternate or adjacent-1 segregation?

> Two phenotypically normal parents produce a phenotypically abnormal child in which chromosome 5 is missing part of its long arm but has a piece of chromosome 7 attached to it. The child also has one normal copy of chromosome 5 and two normal copies of ch

> A phenotypically normal individual has the following combinations of normal and abnormal chromosomes: The normal chromosomes are shown on the left in each pair. Suggest a series of events (breaks, translocations, crossovers, etc.) that may have produced