Module 3.1 Flashcards
DNA or deoxyribonucleic acid is a macromolecule composed of a chain of __________.
nucleotides
Each nucleotide is composed of a pentose sugar called _________, which has a ________ group attached to its 4th carbon, and a ________attached to its 1st carbon.
deoxyribose,
phosphate group,
nitrogenous base
Adjacent nucleotides are joined by _________, which forms through condensation accompanied by the release of water.
phosphodiester bond
The two DNA strands are
antiparallel
the upper end of the _______ strand is labelled 5’ end while the _____ strand is labelled 3’ end.
left,
right
backbone of the DNA molecule
sugar and phosphate
2 types of nitrogenous bases
purines and pyrimidines
purines (2)
Adenine and Guanine
(All Gods are Pure)
pyrimidines (2)
cytosine and thymine
have double ring structures
purines
have single ring structures
pyrimidines
base pairing of the nitrogenous bases and why
A-T and G-C (purines-pyrimidines) since if
purine-purine: not enough space
pyrimidine-pyrimidine: too much space
A-C and G-T: do not fit well together, they do not easily form H bonds.
what bonds form between G-C and A-T pairs
hydrogen bonds
T or F.
H bonds are weak bonds, so DNA molecule don’t have a stable structure.
Although H bonds are weak bonds, so many of them in the entire DNA molecule can give the DNA molecule a stable structure.
3 H bonds - G-C
2 H bonds - A-T
discovered Chargaff’s rule of base-pairing
Erwin Chargaff
states that in a given DNA molecule, there should be the same number of adenine and thymine and the same guanine and cytosine.
was a big help to Watson and Crick when they were developing their base pair model for the double helix structure of DNA.
Chargaff’s rule
Prokaryotic cells usually have a single chromosome and one or a few _______, which are extrachromosomal DNA molecules with their own replicons that carry non-essential genes
plasmids
plasmid function (3)
- increase adaptation of their host cells to specific environments
- aid growth in specific conditions
- encode antibiotic resistance
T or F
Prokaryotic chromosomes are almost always circular. They are either completely devoid of centromeres or carry the so-called “plasmid centromeres” which are not essential.
True
In terms of condensation and packing, _______ appears naked in that the isolated nucleoids look like a collection of wire loops, loosely held together by a proteinaceous core. _______ are always known to segregate continuously, as they replicate, and without additional condensation.
prokaryotic DNA, Prokaryotic nucleoids
Supercoiling, which is one way that prokaryotes compress their DNA into smaller spaces, is made possible with the help of unique _________.
topoisomerases
Supercoils are either negative or right-handed or positive or left-handed supercoil. Mesophilic prokaryotes use DNA gyrase to create _______ while thermophilic prokaryotes use reverse gyrase to create __________.
negative supercoils; positive supercoils
Genomes can be ___________, meaning that the DNA is twisted in the opposite direction of the double helix, or ________, meaning that the DNA is twisted in the same direction as the double helix.
negatively supercoiled;
positively supercoiled (higher temp=maintains double strand)
Most bacterial genomes are (positively/negatively) supercoiled during normal growth
negatively