BIO 148 (Mirabito) Exam 1

A replicated chromosome (pick all that apply) - consists of two identical DNA molecules - consists of two identical sister chromatids - consists of one chromatid - consists of one DNA molecule

- consists of two identical DNA molecules - consists of two identical sister chromatids

The picture below shows a replicated, condensed chromosome consisting of two sister chromatids. How many total DNA molecules are present? - 4 - 1 - Impossible to determine - 8 - 2

2

In the single strand of DNA, there are ______ phosphodiester bonds and ________ hydrogen bonds. - 3, 2 - 2, 0 - 2, 3 - 3, 3 - 3, 0

2, 0

The 3' end of a DNA strand has a free... - ' phosphate group. - 3' nitrogenous base - 3' OH group. - 3' hydrogen atom.

3' OH group

During your summer job at Virotech, you isolate a previously unknown bacterial species. Analysis of its genome reveals that it is composed of a double stranded DNA molecule containing 14% T (thymine). Based on this information, what would you predict the %C (cytosine) to be? - 36% - 72 % - Cannot be determined from the information given. - 14% - 28%

36% (- Each base will have the same percentage as its complementary base. - A is complementary to T, and C is complementary to G. - So if T equals 14%, then A will also equal 14%, accounting for a total of 28% of the DNA. - That leaves 72% of the DNA (100% - 28% = 72%) to split between C and G. - 72% divided by 2 = 36%. So C makes up 36% of the DNA.)

Which of the following nucleotide sequences represents the complement to the DNA strand 5´ - AGATCCG- 3´? - 5´ - AGATCCG- 3 - 3´ - AGATCCG- 5´ - 5´ - CTCGAAT- 3´ - 3´ - TCTAGGC- 5'

3´ - TCTAGGC- 5'

The cell at left is beginning mitosis. How many chromosomes will be in each daughter cell from the cell at the end of mitosis and cytokinesis? - 4 - 16 - 2 - 8 - 1

4 (The cell above has 4 sister chromatids, so each daughter cell would end up with 4 chromosomes.)

This is a picture of my friend's chromosomes isolated in prophase of mitosis. How many chromosomes are present in the picture below? - 46 - 23 - 92

46

Humans have 46 chromosomes in each of their cells in G1 phase. How many chromosomes do we have in each of our cells during G2 phase? - 92 - too many to count - 46 - 23

46 (The number of chromosomes does not change between G1 and G2 phases. The number of chromatids (DNA molecules) doubles, but the number of chromosomes does not.)

There are ____ chromosomes in a human cell before mitosis and ___ chromosomes after mitosis and cytokinesis. - 23, 23 - 23, 46 - 46, 46 - 92, 46

46, 46

A cell has 6 chromosomes in G1 phase. How many DNA molecules are in the cell during G1 phase? - Too many to count - 6 - 12 - 3

6 (During G1 phase, the cellular contents duplicate, but the DNA does not. Each cell therefore has 6 chromosomes in the form of 6 single chromatids, and each chromatid is one molecule of DNA.)

How many DNA molecules are present in the picture above? - 23 - 92 - 46

92

When does DNA replication occur? - Before a cell divides - During cell division - After cell division

Before a cell divides

Cell A has 5 picograms of DNA. Cell B has 10 picograms of DNA. Both cells are from the same organism. Which of the following is the best description of the cell cycle stage of each cell? - Cell A is in G1 phase; Cell B is in S phase - Cell A is in G1 phase; Cell B is in G2 phase - Cell A is in prophase of mitosis; Cell B is in metaphase of mitosis - Cell A is in G2 phase; Cell B is between G1 and S phase

Cell A is in G1 phase; Cell B is in G2 phase Since the DNA replicates during S phase, a cell in G2 phase would have twice as much DNA as a cell in G1 phase.

Rosalind Franklin's data indicated that: - DNA consists of 4 different nucleotides - A=T - DNA has the shape of a helix - DNA is made of amino acids - DNA is transcribed into RNA

DNA has the shape of a helix

Which of these DNA molecules would require the most energy to separate DNA strands? (Hint: think hydrogen bonds) - DNA molecule with 40% guanine bases - DNA molecule with 30% guanine bases - All of the above would require equal energy - DNA molecule with 20% guanine bases

DNA molecule with 40% guanine bases

After one round of replication during the Meselson-Stahl experiment.... - DNA molecules consisted of one heavy strand and one light strand - All DNA strands were a mix of heavy and light DNA - DNA molecules consisted of either 2 heavy or 2 light strands

DNA molecules consisted of one heavy strand and one light strand

Which of the following scenarios would result in a band at intermediate density? Choose the answer that includes all the correct answer choices... - DNA molecules that consist of one heavy strand and one light strand and C. DNA strands that are an equal mix of heavy and light DNA - DNA strands that are an equal mix of heavy and light DNA - DNA molecules that consist of either 2 heavy or 2 light strands - DNA molecules that consist of one heavy strand and one light strand - DNA molecules that consist of one heavy strand and one light strand, DNA molecules that consist of either 2 heavy or 2 light strands and DNA strands that are an equal mix of heavy and light DNA

DNA molecules that consist of one heavy strand and one light strand and C. DNA strands that are an equal mix of heavy and light DNA

Which of the following statements is true of DNA synthesis? - DNA polymerases catalyze the random addition of monomers to the DNA polymer chain. - DNA polymerases work in the 3' → 5' direction by adding nucleotides to complete the complementary strand. - DNA polymerase adds nucleotides to the end of the template strand - DNA polymerase requires a single-stranded template plus a primer to synthesize DNA

DNA polymerase adds nucleotides to the end of the template strand

All of the following were pieces of evidence that Watson and Crick used to help them solve the structure of DNA EXCEPT: - DNA has a constant width. - DNA has a helical structure - In a given DNA molecule, the number of A=T and G=C. - DNA strands are antiparallel

DNA strands are antiparallel

In reference to the same chromosome as the previous question, how is "old" and "new" DNA distributed across the chromosome? - Each sister chromatid consists of one strand old and one strand new - Each sister chromatid is a mix of old and new, but the ratio of old to new in each is difficult to predict - One sister chromatid is old, one is new

Each sister chromatid consists of one strand old and one strand new

A chromosome consists of one DNA molecule. Which phase of the cell cycle is the cell in? - Any of these is possible - S - G1 - G2

G1

Which DNA strands during DNA synthesis are synthesized in the 3' to 5' direction? - Lagging strands - All strands - No strands - Leading strands

No strands

The bottom sequence below represents a DNA strand in the process of being replicated. The top sequence is a complete RNA primer. What DNA nucleotide will be added next to the primer? 5' UUUCGCGU 3' 3' TTCAAAGCGCATGC 5' - Nucleotide with a "U" base - Nucleotide with a "C" base - Nucleotide with a "T" base - Nucleotide with a " A" base - Nucleotide with a "G" base

Nucleotide with a " A" base

The figure below is an illustration of a double-stranded DNA molecule. The 3' end of the strand on the left is labeled. Which nucleotide was the last nucleotide added during synthesis of the lefthand strand? - Nucleotide with a C base - Nucleotide with a T base - Nucleotide with an A base - Nucleotide with a G base

Nucleotide with a G base (DNA replication always moves from the 5' to 3', which means the final nucleotide will be added at 3'.)

Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described? - One end has a hydroxyl group on the 2' carbon; the other end has a hydrogen atom on the 2'carbon. - One end has an unlinked -OH group on the 3' carbon; the other end has an unlinked 5' phosphate group - One end has one phosphate group; the other end has two phosphate group - One end contains a nitrogenous base; the other end lacks it

One end has an unlinked -OH group on the 3' carbon; the other end has an unlinked 5' phosphate group (Organic chemists number the carbons in a molecule, as shown in the super-simplified diagrams below. The sugar that is found in DNA is called deoxyribose and contains 5 carbons (labeled below as 1', 2', 3', 4', 5') and an oxygen (labeled O). A nucleotide is formed when an —OH group and a phosphate group are both added to the sugar. The —OH group is added to the 3' carbon on the sugar. The phosphate group is added to the 5' carbon that hangs off the sugar.)

X-rays can break the sugar-phosphate backbone of DNA. What type of bond breaks when this occurs? - Hydrogen bond - Hydroxyl bond - Nitrogenous bond - Phosphodiester Bond

Phosphodiester Bond

Human chromosome 2 is pictured below. What stage of the cell cycle might it be in? - G1 phase - S-phase - Prophase - Telophase of mitosis - Anaphase

Prophase (During prophase the DNA condenses into the tight formation we recognize as a chromosome.)

How does the structure of DNA hold the information needed to code for the many features of multicellular organisms? - The amino acids that make up the DNA molecule contain the information needed to make cellular proteins. - The width of the double helix changes at each gene due to differences in hydrogen bonds - The hydrogen bonding among backbone constituents carries coded information - The base sequence of DNA carries all the information needed to code for proteins

The base sequence of DNA carries all the information needed to code for proteins (The nitrogenous bases (A, C, T and G) hold the information in DNA. The nitrogenous bases are shown on the image)

What is the difference between the leading strand and the lagging strand in DNA replication? - The leading strand requires an RNA primer, whereas the lagging strand does not - The leading strand is synthesized continuously in the 5′→3′ direction, while the lagging strand is synthesized discontinuously in the 5′→3′ direction. - The leading strand is synthesized in the 3′→5′ direction in a discontinuous fashion, while the lagging strand is synthesized in the 5′→3′ direction in a continuous fashion.

The leading strand is synthesized continuously in the 5′→3′ direction, while the lagging strand is synthesized discontinuously in the 5′→3′ direction.

Which of the following is involved in phosphodiester bond formation? - a phosphate group from one nucleotide and an ester group from another nucleotide. - The phosphate of a nucleotide's 5' carbon and the hydroxyl group of a nucleotide's 3' carbon. - The hydroxyl group of a nucleotide's 5' carbon and the phosphate of a nucleotide's 3' carbon - Two hydroxyl groups from the sugars of the nucleotides.

The phosphate of a nucleotide's 5' carbon and the hydroxyl group of a nucleotide's 3' carbon.

Which of the following statements about sister chromatids is TRUE? - Each chromatid consists of one strand of a double-stranded DNA molecule - They are formed as the result of semiconservative DNA replication - They are held together during anaphase of mitosis - They are part of the same chromosome in G1 phase.

They are formed as the result of semiconservative DNA replication (Like all DNA, they are formed by semi-conservative replication.)

A single chromosome can contain either one DNA molecule or two identical DNA molecules held together. - False - True

True

In which of the following figures would a G (nucleotide with a guanine base) be the next nucleotide added? Hint: The nucleotide is added to a free -OH group. - d - a - c - b

a (G is the complementary base to C.)

In the Meselson-Stahl experiment, three potential models of DNA replication were tested. Cells were grown in heavy nitrogen (N15), which incorporated into the bases (Generation 0). The cells were then switched to medium that contained light nitrogen (N14) and allowed to replicate two times (Generation 1 and 2). If the conservative model of DNA replication were true, what would have Meselson and Stahl observed in the tubes after one round of DNA replication? Choose the letter corresponding to the correct figure below. - d - a - b - c

a (If replication was conservative, then half of the DNA would be heavy and half would be light. If it was semi-conservative then half would be light and half would be intermediate.)

Suppose that Meselson and Stahl first grew cells in light nitrogen (Generation 0) and switched to heavy nitrogen (N15) for one round of replication. If the conservative model of DNA replication were true, what would have Meselson and Stahl observed in the tubes after one round of DNA replication? Choose the letter corresponding to the correct drawing below. - b - a - d - c

a (The result would be half light and half heavy)

When nucleotides polymerize to form a nucleic acid, _____. - hydrogen bonds form between the bases of two nucleotides within a single strand - a covalent bond forms between the sugar of one nucleotide and the phosphate of a second - covalent bonds form between the bases of two nucleotides within a single strand - a hydrogen bond forms between the sugar of one nucleotide and the phosphate of a second

a covalent bond forms between the sugar of one nucleotide and the phosphate of a second (Make sure you know the following terms: Polymerize: To add repeating molecules together to form a chain, like stringing beads on a necklace. Covalent bond: A strong bond between molecules that share electrons. (Contrast that with a weak hydrogen bond, where electrons are not shared.))

The model below depicts a single strand of template DNA (bottom line) and a complete RNA primer (top line). Which arrow points to the end where the first DNA nucleotide will be added by DNA polymerase? Choose the letter corresponding to the correct arrow below. - a - c - b - d

b (DNA polymerase will add the new nucleotides in a 5' to 3' direction)

In G1 phase, - cells are preparing for cell division - DNA is being replicated - cells are dividing - cells are carrying out their normal cellular functions

cells are carrying out their normal cellular functions

During G1 phase, - Chromosomes are in the process of replication - Chromosomes consist of two identical DNA molecules - chromosomes consist of one long DNA molecule and associated proteins - Chromosomes consist of one long DNA strand

chromosomes consist of one long DNA molecule and associated proteins

In a DNA double helix, the chemical bonds that form between nucleotides to create the DNA backbone are... - covalent bonds - hydrophobic bonds - ionic bonds - hydrogen bonds

covalent bonds (they are covalent phosphodiester bonds)

Suppose that Meselson and Stahl first grew cells in light nitrogen (Generation 0) and switched to heavy nitrogen (N15) for two rounds of replication. If the semiconservative model of DNA replication were true, what would have Meselson and Stahl observed in the tubes after two rounds of DNA replication? Choose the letter corresponding to the correct drawing below. - b - d - a - c

d (Half of the DNA would be heavy and half would be intermediate)

Which of the cells below corresponds to a cell in telophase? - d - a - e - b - c

e

In a DNA double helix, the chemical bonds that form between the complementary nitrogenous bases are... - hydrophobic bonds - hydrogen bonds - covalent bonds - ionic bonds

hydrogen bonds

Scientists isolate cells from an individual in various phases of the cell cycle. They find a group of cells that have 1½ times more DNA than do G1 phase cells. The cells of this group are _____. - between the G1 and S phases in the cell cycle - in the M phase of the cell cycle - in the G2 phase of the cell cycle - in the S phase of the cell cycle

in the S phase of the cell cycle (During S phase, the DNA replicates, so a group of cells with 1 1/2 times more DNA would be partway through S phase.)

The monomer unit of DNA is a... - Sugar-phosphate - Phosphodiester - Nucleic acid - Nucleotide - Deoxyribose suga

nucleotide

S phase of the cell cycle corresponds to _____. - the phase between DNA replication and the M phase - the only phase for normal growth and cell function - the beginning of mitosis - the phase in which DNA is being replicated

the phase in which DNA is being replicated

The DNA in all your cells is, for the most part, the same - true - false

true

All cells contain DNA that is made up of ______ that are ________ and ________ to each other. - two DNA strands; identical; parallel - two DNA strands; identical; antiparallel - two DNA molecules; identical; antiparallel - two DNA strands; complementary; antiparallel - two DNA strands; complementary; parallel

two DNA strands; complementary; antiparallel