BIO 111 DNA structure and replication
Cytosine makes up 30% of the nucleotides in a sample of DNA from an organism. What percent of the nucleotides in this sample will be thymine?
20
Given the nucleotide sequence 5' - CATTAGATCG-3' find the complementary DNA strand
3'-GTAATCTAGC-5'
Which would you expect of a eukaryotic cell lacking telomerase?
A reduction in chromosome length
Which answer correctly summarizes the findings of Erwin Chargraff?
A=T; G=C
The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?
Adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn
In the ladder analogy of the structure of DNA, the uprights are composed of
Alternating deoxyribose and phosphate groups
For a science project 2 students decided to repeat the Hershey and Chase experiment, with modifications. They decide that labeling the phosphates of the DNA wasn't good enough. Each nucleotide has only 1 phosphate, whereas each nitrogenous base has 2-5 nitrogens. Thus, labeling the nitrogenous base would provide a stronger label than labeling the phosphates. This experiment won't work because
Amino acids (and thus proteins) also have nitrogen atoms, this the radioactivity would not distinguish between DNA and proteins.
What is the function of DNA ligase
Covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
The sub-units that constitute the backbones of a DNA molecule (rails in the ladder analogy) are held together by
Covalent bonds between sugar molecules and phosphate groups
Which enzyme catalyzes the elongation of a DNA strand in the 5'-3' direction
DNA polymerase III
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end.
The enzymes that actually catalyze the synthesis of a new DNA strand are called
DNA polymerases
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which?
Gaps left at the 5' end of the lagging strand because of the need for a 4' onto which nucleotides can attach
Which of the statements is true of chromatin
Heterochromatin is highly condensed, whereas euchromatin is less compact
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged
What kind of chemical bonds are found between paired bases of the DNA double helix?
Hydrogen
During DNA replication, synthesis of the lagging strand is discontinuous and forms short segments of DNA known as
Okazaki fragments
Replication in prokaryotes differs from replication in eukaryotes for which of the reasons?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
It is unknown what the genetic material for the organisms that live on planet X is. Based on some observations, you suspect that on the planet, it is protein that serves as the genetic material.
Radioactive sulfur will be associated with infected cells but radioactive phosphorous will not.
The site on a replacing DNA molecule at which the old strands are being separated is known as the
Replication fork
DNA replication occurs during ___ of the cell cycle
S phase
All of the following elements are present in DNA except
Sulfur
Which of the following statements does not apply to the Watson and Crick model of DNA?
The 2 strands of the helix are held together by covalent bonds
What determines the nucleotide sequence of the newly synthesized strand during DNA replication
The nucleotide sequence of the template strand
All of the following were determined directly from x-ray diffracting photographs of crystallized DNA except
The specificity of base pairing
What is the function of DNA polymerase?
To add nucleotides to the end of a growing DNA strand
The nitrogenous bases____ contain 2 nitrogenous rings and are known as
adenine and guanine; purines
Since the 5' to 3' direction of one strand of the DNA molecule is opposite to that of the other, the strands are said to be
anti-parallel
A DNA nucleotide consists of
deoxyribose plus a base plus a phosphate
The base sequence of DNA in eukaryotic organisms
differs from 1 species to the next
The enzymes that break the H bonds between complementary base pairs during DNA replication are
helicases
The function of single-strand binding proteins in DNA replication is to
hold the unwound single strands apart so they do not kink
DNA replication is called semi-conservative because
one parent strand goes to each of the 2 daughter strands
The specific nucleotide sequence at which DNA replication is initiated is known as the
origin of replication
In the ladder analogy of DNA structure, the rungs of the ladder are
paired nitrogen bases.
During DNA replication, each strand acts as a ___ since it serves as a pattern for the generation of a new
template; complementary strand
If radioactive sulfur is used in the culture medium of bacteria that harbor phage viruses, it will later appear in the
viral coats