Genetics Lecture Exam 1

If you were evaluating double-stranded samples of DNA, which of the following relationships must be true?

(A + G)= (T + C); (A + C) =(T + G)

Five samples of nucleic acids were analyzed for base composition with the following results. Which one was most probably a single stranded DNA sample?

13%=A, 21%=G, 36%=T, and 30%=C.

If protein were the genetic principle and not nucleic acid, significant mutagenic effects would be detected at ________.

280 nm

DNA is extracted from the blood contained in a fossilized mosquito (uh oh!). The genetic material from the blood sample was found to be DNA and constructed according to the WatsonCrick model. This sample was determined to contain 20% guanine. How much adenine should it contain?

30%

DNA was extracted from a recently captured creature which resembled anelephant. Although this creature was in very poor physical condition due to a severebeating inflicted by a gator, it was initially thought to be a new type of lower lifeform. Analysis of its DNA, however, showed it to be constructed according to theWatson - Crick Model. The DNA sample was determined to contain 20% guanine.How much thymine should it contain?

30%

In a sample of double stranded DNA, 15% of the nucleotides are adenine. Which of the following statements is most likely true?

35% are guanine. (DS DNA --> A=T and G=C)

In a species where 2N=4X=8, what is the haploid number?

4

The sugar found in DNA has 5 carbon atoms. How many carbon atoms are in thesugar found in RNA?

5

A given piece of single stranded DNA reads 5' CGTATTCA 3'. Which of thefollowing could form a normal, complimentary double helix with this sequence?

5' TGAATACG 3'

Put the following events of mitosis in the correct order.1. centromeres divide2. chromosomes relax and uncoil3. spindle fibers attach to centromeres4. chromosomes arrive at each pole5. chromosomes condense

5, 3, 1, 4, 2

Which of the following samples of DNA is expected to have the highest melting temperature?

60% G-C content (G-C has 3 hydrogen bonds making it stronger and harder to break)

In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?

A + C = G + T

Which if the following components is included in every nucleotide?

A pentose sugar (nucleotide contains a pentose sugar (DNA or ribose in RNA) every nucleotide contains a phosphate and a nitrogenous base.)

Spleen diesterase is an enzyme that breaks the covalent bond that connects the phosphate to the 5' carbon. If the dinucleotide is digested with spleen diesterase, to which base and to which carbon on the sugar is the phosphate now attached?

A; 3'

Which scientists identified the transforming principle?

Avery, McCarty and MacLeod

Which form of DNA is most commonly found in nature?

B (B-DNA was one of the first known and studied. It is a right handed helix and it exists under aqueous conditions and at salinity levels consistent with living organisms. )

Which of the following outcomes would be most likely if the Hershey-Chase experiments were repeated without the step involving the blender?

Both preparations of infected bacteria would exhibit radioactivity.

Characteristics of RNA

Contain uracil; single-stranded; contains ribose as a sugar

Characteristics of DNA

Contains deoxyribose, is made up of two strands, and has Thymine.

Nucleosomes are structures composed of:

DNA and histone proteins.

Which of the following molecules is a major component of eukaryotic chromosomes?

DNA and protein (The DNA holds the essential information necessary to determine the phenotypes the cell expresses. The proteins are used to maintain the structure of the DNA)

Which of the following statements is true?

DNA contains deoxyribose.

An experiment by Hershey and Chase provided evidence that DNA is the geneticmaterial. Which of the following facts allowed them to document the function ofDNA?

DNA contains phosphorus but no sulphur, and protein contains sulphur but no phosphorous.

Which of the following statements is NOT evidence that DNA, and not protein, is the genetic material in eukaryotes as well as bacteria?

DNA has four nucleotides

The Central Dogma specifies that the information in ________.

DNA is copied into an RNA molecule during transcription, and the information in that RNA molecule is used to make a protein during translation

What significant genetic function occurs in the S phase of the cell cycle?

DNA synthesis

Cells that are metabolically active, but not destined to proliferate are said to be in _______.

G0 phase (When cells are in G0 phase, they have withdrawn from the cell cycle and do not proliferate)

At which phase(s) of the cell cycle would a cell normally check for the integrity of its DNA?

G1/S and G2/M phases (The G1/S checkpoint monitors cell size and checks for damaged DNA. The G2/M checkpoint monitors whether DNA replication and repair to any damaged DNA has been completed)

Who discovered the transforming principle in Streptococcus pneumonia?

Griffith (Griffith made an accidental discovery about bacterial species and their ability to transform the phenotypes of other bacteria)

Which scientists provided evidence supporting DNA as the genetic material by conducting experiments with Escherichia coli and its infecting virus, bacteriophage T2?

Hershey and Chase

What are histones, and how are they arranged in nucleosomes?

Histones include five main classes of relatively small basic proteins containing relatively large amounts of lysine and arginine. Nucleosomes are made of two each of four types of histones.

Which of the following are true about the two strands of the double helix?

Hydrogen bonds hold the two polynucleotide strands together; The hydrophobic nitrogenous bases are located in the center of the molecule, whereas the hydrophilic phosphodiester backbone is on the outside; The two strands are antiparallel.

In the formation of nucleosomes, one histone class, H1, is not directly involved, yet it does associate with DNA to form higher level chromosomal structures. Where does this histone (H1) associate?

It binds to linker (spacer) DNA between nucleosomes.

What is the function of transfer RNA (tRNA)?

It is the adapter between mRNA and amino acids during translation. (tRNA is the adapter between mRNA and amino acids during polypeptide synthesis)

What is the function of messenger RNA (mRNA)?

It is the template for polypeptide production

Which of the following is true of negatively supercoiled DNA?

It is underwound.

Which acidic substance was isolated from cell nuclei by Friedrich Miescher in 1869?

Nuclein

Which type of bond connects two nucleotides and includes a phosphate connected to the sugar of both nucleotides?

Phosphodiester (connecting the sugars of two nucleotides, using a shared phosphate between them)

Which of the following is not a tenet of the central dogma of molecular genetics?

Proteins are the template for DNA production. (There is no mechanism for proteins to serve as a template for DNA synthesis.)

Which of the following molecules was used in the Hershey-Chase experiment?

Proteins were radiolabeled with 35S and DNA was radiolabeled with 32P.

Which characteristic must be exhibited by a molecule in order for it to be used as the genetic material in an organism?

Replication, information storage, expression of information, and variation by mutation

Which enzyme can use an RNA template to produce DNA?

Reverse transcriptase (One category of viruses, the retroviruses, can use RNA as a template for DNA synthesis. The enzyme used in this process is called reverse transcriptase )

What is the function of ribosomal RNA?

Ribosomal RNA is a major component of ribosomes. (Ribosomal RNA forms a spherical complex, in association with a small cluster of proteins, to create a ribosome)

Which scientist confirmed the helical nature of DNA using X-ray diffraction?

Rosalind Franklin (used highly purified samples of DNA and performed X-ray crystallography)

What is the arrangement of chromosomes during metaphase?

Sister chromatids align along the equatorial plane of the cell.

Which type of virus was used in Hershey-Chase experiment?

T2 bacteriophage

In the classic experiment conducted by Hershey and Chase, why was the pellet radioactive in the centrifuge tube that contained bacteria with viruses?

The bacteria were in the pellet, and many contained the radioactive viral DNA

Which of the following are true about nitrogenous bases and base pairing?

The base composition is such that A equals T and G equals C; There are two hydrogen bonds forming the A to T pair and three forming the G to C pair; Bases are stacked 0.34 nm apart.

Why is Tm related to base composition? Which statement is true?

The more hydrogen bonds between bases, the higher the temperature needed to separate the pair; G-C base pairs have three hydrogen bonds while A-T base pairs have two hydrogen bonds.

Which of the following statements about the basic structural features of DNA are true?

The twisting of the DNA double helix is attributed to the tight packing of DNA bases and base-stacking; In a DNA macromolecule, the two strands are complementary and antiparallel.

Which of the following is true about the overall structure of the DNA helix?

There is one complete turn for each 3.4 nm, which constitutes 10 bases per turn; The double helix is approximately 20 Angstroms in diameter; The double helix is right-handed.

Viral genomes and eukaryotic genomes are similar in which of the following ways?

They have the ability to pack a genome into a small volume. (Both eukaryotic and viral genomes can be characterized by their ability to pack DNA into a small volume)

The base content of a sample of nucleic acid is as follows: A = 31%, G = 31%, T = 19%, C = 19%. What conclusion should be drawn from this information?

This nucleic acid is single-stranded DNA

Which of the following statements best describes Chargaff's base-paring rule observed in double stranded DNA?

Total # purines = total # pyrimidines, and proportion of adenine = proportion of thymine, and proportion of cytosine = proportion of guanine.

Briefly define transformation and describe the relationship between the phenomenon of transformation and the discovery that DNA is the genetic material in bacteria.

Transformation is the process whereby one organism is genetically altered by exposure to DNA from another organism. Since DNA can carry heritable "traits" from one organism to another, it must be the genetic material.

Who proposed the widely accepted 3D model of DNA?

Watson and Crick

Which form of DNA includes only G-C base pairs?

Z (Z-DNA was discovered in 1979; it is a left handed helix that includes only guanine and cytosine.)

The Z form of DNA is:

a left-handed double helix.

n class, we learned that the two strands of a double helix have a constant distance between them. What single feature of the structure of a DNA molecule is most important for insuring that this is true?

a purine always pairs with a pyrimidine and vice-versa.

A __________ chromosome has its centromere located very close to, but not on, the end of the chromosome.

acrocentric

Which chromosome has a telomere but the p arm is much shorter than the q arm?

acrocentric

Eukaryotic chromosomes contain two general domains that relate to the degreeof condensation. These two regions are ________.

called heterochromatin and euchromatin

Messenger RNA (mRNA)

carries information from the nucleus to the cytoplasm; sequence specifies the order of amino acids in a protein

Ribosomal RNA (rRNA)

catalyzes peptide bonds between amino acids; structural part of enzyme used for translation

Both DNA and RNA

contains A, G, C, and a phosphate group

Deoxyribonucleotides are added to each other forming a polynucleotide chainin a 5' to 3' direction. How are these nucleotides linked to each other?

covalent bonding between phosphate and sugar.

replication

duplication of genetic material

Living organisms are categorized into two major groups based on the presence or absence of a nucleus. What group is defined by the presence of a nucleus?

eukaryotic organism

The second order of chromatin packing occurs when nucleosomes coil together to form a fiber that is 300 nm in diameter.

false

A particular ________ carry the information for making a particular protein, but ________ can be used to make any protein.

gene and mRNA; a ribosome and a tRNA

A nucleotide sequence is known to contain a pyrimidine as the fourth base of the sequence. What nucleotide could not be found in the fourth position in either DNA or RNA?

guanine

Considering the structure of double-stranded DNA, which kind(s) of bonds hold one complementary strand to the other?

hydrogen

Based on the WatsonCrick model of DNA structure, which of the following statements is (are) true?

if the percentage of one nitrogenous base is known, the percentage of the other nitrogenous bases are known.

To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _______.

incubated nonvirulent cells with the complete extract

Which of the following is NOT a characteristic of the genetic material?

it is composed of protein

Transfer RNA (tRNA)

link between codons and amino acids; has a cloverleaf secondary structure

Which type of RNA is the least stable?

mRNA

Compared with B-DNA, A-DNA is ________ compact, has ________ base pairs per turn, and is a ________ helix.

more; fewer; right-handed

In the bacterial transformation experiments of Avery, MacLeod and McCarty,when the transforming principle was treated with DNase, the result was:

no transformation occurred.

In the mid-1940s, genetic information was known to consist of ________.

nucleic acid and protein

The major repeating unit of nucleic acids is the nucleotide. It is composed of

nucleoside and phosphate.

Why are the two strands in a double helix said to be antiparallel to each other?

one strand is 3' → 5' and the other strand is 5' → 3' when viewed together.

If Avery had observed transformation using only the extracts containing degraded DNA, degraded RNA, and degraded protein, but NOT the extract containing degraded polysaccharides, he would have concluded that _______.

polysaccharides are the genetic material

variation

potential for alteration

expression

production of a phenotype

Which type of bacterium can be infected with DNA extracts from T2 phages, even in the absence of the phage protein coat?

protoplast (Protoplasts can be infected by phage DNA without a viral protein coat.)

What are the three major types of RNA molecules?

ribosomal RNA transfer RNA messenger RNA

Which of the following cell structures is directly involved in protein synthesis?

rough endoplasmic reticulum and ribosomes

Which of the following pathogens have an RNA genome?

some viruses (Some viruses contain an RNA genome, while others contain a DNA genome.)

storage

stable maintenance and passage of information

Any molecule that serves as the genetic material must have the followingcharacteristics except _____.

the ability to directly influence the development of traits.

If all the phosphodiester bonds in a DNA double helix were to break at once:

the helix would remain intact due to hydrogen bonding.

Many important experiments require that DNA be denatured. What happenswhen DNA is denatured by heat?

the hydrogen bonds between nitrogen bases are broken.

What would have happened in Griffith's transformation experiment withvirulent and avirulent strains of bacteria if he had mixed heat-killed virulentbacteria with living avirulent bacteria and injected this mixture into live mice?

the same thing as if he had just injected living virulent bacteria.

Two double helix DNA molecules of equal length are melted. The first dissociates at a lower temperature than the second. What would this indicate about the relative contents of nucleotides in the two molecules?

the second molecule has a higher content of CG base pairs than the first molecule

If you mix denatured strands of DNA with strands of RNA and they hybridize,what property of the two nucleic acids is demonstrated?

they are partially or completely complimentary.

The purines and pyrimidines found in DNA pair in a precise manner, leading us to the concept of complementarity or base complementation. Which of the following is accurate with respect to the pairing relationships?

thymine with adenine and cytosine with guanine

Avery, McCleod, and McCarty conducted experiments which provided evidencethat DNA is the genetic material. Which answer best describes the results of thethree experiments shown below?Experiment 1: IIR + (IIIS extract treated with RNase) = ?Experiment 2: IIR + (IIIS extract treated with Protease) = ?Experiment 3: IIR + (IIIS extract treated with DNase) = ?

transformations were observed in Experiments 1 and 2 but not Experiment 3.

What makes up the protein component of a nucleosome?

two tetramers of histone proteins (The protein component of a nucleosome is composed of two tetramers of histone proteins. One tetramer is composed of two units each of histones H2A and H2B, and the other is composed of two units each of histones H3 and H4.)

Some white fibrous material is extracted from a cell. It is thought to be DNA, RNA, or protein. You could show that this material is actually RNA and not the others by the presence of

uracil