Cellular Biology Chapter 5

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?

DNA was found to contain only four different chemical building blocks.

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

Do any chromosomes contain point mutations?

Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists obtained definitive results demonstrating that DNA is the genetic molecule?

Hershey and Chase

Specific regions of eukaryotic chromosomes contain sequence elements that are absolutely required for the proper transmission of genetic information from a mother cell to each daughter cell. Which of the following is not known to be one of these required elements in eukaryotes?

terminators of replication

Interphase chromosomes are about ____ times less compact that mitotic chromosomes, but still are about _____ times more compact than a DNA molecule in its extended form.

20, 500

Nucleosomes are formed when DNA wraps _____times around the histone octamer in a _____ coil.

1.7, left-handed

Mitotic chromosomes are ______ times more compact than a DNA molecule in its extended form.

10,000

Many of the breakthroughs in modern biology came after Watson and Crick published their model of DNA in 1953. However, chromosomes were identified earlier. In what decade did scientists first identify chromosomes?

1880s

The human genome is a diploid genome. However, when germ-line cells produce gametes, these specialized cells are haploid. What is the total number of chromosomes found in each of the gametes (egg or sperm) in your body?

23

Hershey and Chase used radiolabeled macromolecules to identify the material that contains heritable information. What radioactive material was used to track DNA during this experiment?

32P

The human genome is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body.

46

Which of the following DNA strands can form a DNA duplex by pairing with itself at each position?

5'-AAGCGTT-3'

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'

5'-CTACCCACGAATGC-3'

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion?

Double-stranded genomes have equal amounts of A and T

Histone proteins have a lower-than-average number of lysines and arginines in their polypeptide chains.

False

Interphase chromosomes represent a physical state of the chromatin with the highest order of packaging.

False

T/F All functional DNA sequences inside a cell code for protein products.

False

T/F Comparing the relative number of chromosome pairs is a good way to determine whether two species are closely related.

False

T/F DNA molecules, like proteins, consist of a singe, long, polymeric chain that is assembled from small monomeric subunits.

False

T/F Gene expression is the process of duplicating genes during DNA replication.

False

T/F Gene sequences correspond exactly to the respective protein sequences produced from them.

False

T/F Hydrogen bonds between each nucleotide hold individual DNA strands together.

False

T/F The histone proteins that constitute the core nucleosome include tetramers of histones H2A, H2B, H3, and H4.

False

T/F The telomere is a specialized DNA sequence where microtubules from the mitotic spindle attach to the chromosome so that duplicate copies move to opposite ends of the dividing cell.

False

T/F There are five different nucleotides that become incorporate into a DNA strand.

False

The core histones are small, basic proteins that have a globular domain at the C-terminus and a long, extended conformation at the N-terminus. Which of the following is not trued of the N-terminal "tail" of these histones.

It binds to DNA in a sequence-specific manner.

The information stored in the DNA sequences is used directly as a template to make:

RNA

How do changes in histone modification lead to changes in chromatin structure?

They help recruit other proteins to the chromatin

Which of the following best describes the mechanism by which chromatin-remodeling complexes "loosen" the DNA wrapped around the core histones?

They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer.

T/F Chromosomes exists at different levels of condensation, depending on the stage of the cell cycle.

True

T/F Each strand of DNA contains all the information needed to create a new double- stranded DNA molecule with the same sequence information.

True

T/F Eukaryotic chromosomes contain many different sites where DNA replication can be initiated.

True

T/F Liner histones help compact genomic DNA by influencing the path of the DNA after it has wrapped about the nucleosome core.

True

T/F The polarity of a DNA strand results from the polarity of the nucleotide subunits.

True

Mitotic chromosomes were first visualized with the use of very simple tools: a basic light microscope and some dyes. Which of the following characteristics of mitotic chromosomes reflects how they were named?

color

When there is a well-established segment of heterochromatin on an interphase chromosome, there is usually a special barrier sequence that prevents the heterochromatin from expanding along the entire chromosome. Gene A, which is normally expressed, has been moved by DNA recombination near an area of heterochromatin. None of the daughter cells produced after this recombination event express gene A, even though its DNA sequence is unchanged. What is the best way to describe what has happened to the function of gene A in these cells?

epigenetic inheritance

Stepwise condensation of linear DNA happens in five different packing processes. Which of the following four processes has a direct requirement for histone H1?

formation of the 30-nm fiber

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?

gene silencing

The manner in which a gene sequence is related to its respective protein sequence is referred to as the _____code.

genetic

The complete set of information found in a given organism's DNA is called its:

genome

Which of the following is not a chemical modification commonly found on core histone N-terminal tails?

hydroxylation

The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and is produced experimentally. Which chromatin components are not retained when this structure is generated.

linker histones

Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing?

lysine 9 methylation

The inactivation of one X chromosome is established by the directed spreading of heterochromatin. The silent state of this chromosome is _______ in the subsequent cell divisions.

maintained

The chromosomes we typically see in images are isolated from mitotic cells. These mitotic chromosomes are n the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and _________.

occupy discrete territories in the nucleus.

What type of macromolecule helps package DNA in eukaryotic chromosomes?

proteins

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

ratio of A+T to G+C

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

six-carbon sugar

In a DNA double helix...

the two DNA strands run antiparallel.

The process of sorting human chromosomes pairs by size an morphology is called karyotyping. A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes "painted"

using florescent DNA molecules

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

using the energy of ATP hydrolysis to move nucleosomes

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

Uniform left-handed twist

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?

Griffith

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?

H1

Most eukaryotic cells only express 20-30% of the genes they posses. The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification directs the formation of the most common type of heterochromatin?

H3 lysine 9 methylation

Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that pathogenic bacteria that have been killed by heating can no longer cause an infection. But when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this experiment?

The heat-killed pathogenic bacteria "transformed" the harmless strain into a lethal one.