Chapter 15: DNA and the gene

If you already know that the infectious agent was either bacterial or viral which menthods listed above would allow you to distinguish between these two possibilities?

1. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope Or 2. Culture the substance on nutritive medium away from any plant cells.

In an analysis of the nucleotide composition of DNA which of the following will be found ?

A +C= G+T

Which is the most current description of a gene ?

A DNA sequence that is expressed to form a functional product: either RNA or polypeptide

base pair for T C T G C T G

A G A C G A C

which of the following would you expect of a eukaryote lacking telomerase ?

A reduction in chromosome length in gametes

Which result would be consistent with the base-pairing rule ?

A+G=C+T

For a science fair project two students decided to repeat the Hershey and chase experiment with modifications, why didn't it work ?

Amino acids (thus proteins ) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins

In trying to determine whether DNA or protein is the genetic material Hershey and chase made use of which of the following facts ?

DNA contains phosphorus whereas protein does not

what would happen if a cell replicates once in the presence of this radioactive base ?

DNA in both daughter cells would be radioactive

what catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed ?

DNA polymerase

name the steps to DNA replication

First- hydrogen bonds between base pairs of antiparallel strands are broken second- single stranded binding proteins attach to dna strands third- Primase binds to the site of origin Fourth- An rna primer is created Fifth- DNA polymerase binds to the template strand

Which of the following characteristics, structures or processes is common to bacteria and viruses ?

Genetic material composed of nucleic acid

Which of the following would be least likely to cause DNA damage to an individual suffering from xeroderma pigmentosum ?

Incandescent light bulbs

the role of DNA ligase is to:

Join Okazaki fragments together

who performed the classic experiments that supported the semiconservative model of DNA replication ?

Meselson and stahl

which of the following are the most prominent types of dna lesions in indiviuals suffering from xeroderma pigmentosum?

Methylation of purines

what is the difference between eukarotic DNA replication and Prokaryotic DNA replication ?

Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple orgins of replication.

polytene chromsomes of drosophila salivary galnds each consist of multiple identical DNA strands that are aligned in parallel arrays. how could these arise ?

Replication without seperation

A bacteium is infected with an experimentally constructed bacteriophage T2 protein and T4 DNA. The new phages produced would have____

T4 protein and T4 DNA

How might adding telomerase affect cellular aging ?

Telomerase eliminates telomere shortening and retards aging.

What appears to be a dark side to telomerase activity with regard to human health ?

Telomerase is active in most cancerous cells

when the rate of repair lags behind the rate of mutation:

The cell can be transformed into a cancerous cell

What is Telomere ?

The ends of linear chromosomes

E. coli had mutation rates that are 100 times higher than normal, why ?

The proof reading mechanism of DNA polymerase was not working properly

Capsids go from being full to being empty which of the following best fits these observations ?

The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane and the genome is all that enters the nucleus

Viruses

Use the host cell to copy themselves and make viral proteins

The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes . This most likely reflects ___

a critical function of telomeres

Eukaryotic telomeres replicate differently than the rest of the chromosomes. This is a consequence of which of the following ?

gaps left at the 5' end of the lagging strand

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes

it catalyzes the lenghthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity

The leading and lagging strands differ in that ___

leading strand: is synthesized in the same direction as the movement of replication lagging strand: is synthesized in the opposite direction

which of the following is least likely to cause mutations in DNA ?

light from an incandescent bulb

Which of the following cells have reduced or very little active telomerase activity ?

most normal somatic cells

DNA replication is highly accurate, For the human genome how often would errors occur?

on average, 6 times each time the entire genome of a cell is replicated.

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations. DNA is centrifuged. (What density distribution of DNA would you expect in this experiment) ?

one low-density and one-intermediate density band

semiconservative replication involves a template. what is the template ?

one strand of the DNA molecule

Telomere shortening is a problem in which types of cells?

only eukaryotic cells

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thyamine and cystosine forms hydrogen bonds with guanine. this arrangement _____

permits complementary base pairing

The epsilon subunit ____

removes a mismatched nucleotide

DNA is synthesized through a process known as _____

semiconservative replication

Which of the following helps to hold the DNA strands apart while they are being replicated ?

single-stranded DNA binding proteins

In the polymerization of dna, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and ____ of the last nucleotide in the polymer

the 3' OH

The kind of gene affected in those with XP is one whose product is involved with _____

the ability to excise single strand damage and replace it

what provides the energy for the polymerization reactions in DNA synthesis ?

the deoxyribonucleotide triphsophate substrates

Xeroderma pigmentosum results from mutations in one of seven genes, what can you infer ?

there are several proteins involved in the nucleotide excision repair process

In E. coli, what is the function of DNA polymerase III ?

to add nucleotides to the 3' end of a growing DNA strand