Week 2 Flashcards
DNA is made up of what two macromolecules?
Protein and Nucleic acids
What are the two types of nucleic acids?
DNA and RNA
What is a Nucleic acid?
Macromolecules composed of repeating subunits called nucleotides
What makes up a nucleotide?
(1) a phosphate group,
(2) a five-carbon sugar, or pentose
(3) a cyclic nitrogen-containing compound called a base
What sugar is used in DNA
In DNA, the sugar is 2-deoxyribose
What is the sugar in RNA?
In RNA, the sugar is ribose
What are the 4 common bases found in DNA?
-Adenine
-Guanine
-Cytosine
-Thymine
What two bases are considered purines?
Adenine and guanine are double-ring bases called purines;
What are the 4 bases found in RNA
-Adenine
-Guanine
-Cytosine
-Uracil
What three bases are considered pyrimidines?
-cytosine, thymine, and uracil are single-ring bases called pyrimidines
What bonds link together nucleotides?
Covalent phosphodiester bonds
What bonds hold together the two polynecleotide chains of the double helix DNA?
Hydrogen Bonding
How many hydrogen bonds are formed between Adenine and Thymine?
two hydrogen bonds
How many hydrogen bonds are formed between Guanine and Cytosine?
three hydrogen bonds
How are the sugar-phosphate backbones of two complementary strands oriented?
antiparallel; parallel but moving or oriented in opposite directions
What is B-DNA and when does this state occur?
-In aqueous solutions
-low salt levels
The vast majority of the DNA molecules present in the aqueous protoplasms of living cells exist in the B conformation (10 nucleotides per turn)
What is A-DNA and when does it take this formation?
-In high concentrations of salts
-or in a partially dehydrated state
A-DNA is shorter and thicker double helix
A right handed helix like B-DNA, but with 11 nucleotide pairs per turn
What is Z-DNA and when does it take on this state?
A left-handed, doublehelical form
(Z for the zigzagged path of the sugar-phosphate backbones of the structure)
Z-DNA occurs in double helices that are G:C-rich and that contain alternating purine and
pyrimidine residues.
Has 12 base pairs per turn; a single deep groove; and much thinner than others
How is DNA organized in all living cells?
It is supercoiled
How are supercoils in DNA formed?
When one or both strands are cleaved
When the complementary strands
at one end are rotated or twisted around each other with the other end held fixed in
space—and thus not allowed to spin
How are most DNA molecules supercoiled in vivo?
negative supercoiling in vivo
At what point can biological functions of chromosomes can be carried out?
only when the participating DNA molecules are negatively supercoiled
