Module 5 Flashcards
A simple polymer composed of four types of chemically related nucleotide subunits
Carries the hereditary information of the cell
DNA Molecule
Isolated nuclein in white blood
cell nuclei (1869)
Friedrich Miescher
Transferred killing ability between types of bacteria (1928)
Frederick Griffith
Discovered that DNA transmits killing ability in bacteria (1940)
Oswald Avery, Colin MacLeod, and Maclyn
McCarty
Determined that the part of a virus that infects and replicates is its nucleic acid and not its protein (1950)
Alfred Hershey and Martha Chase
Discovered DNA components, proportions, and positons (1909-early 1950s)
Phoebus Levene, Erwin Chargaff, Maurice
Wilkins, and Rosalind Franklin
Elucidated DNA’s three dimensional structure (1953)
James Watson and Francis Crick
Had his genome sequenced (2008)
James Watson
A section of a DNA molecule
Sequence of building blocks that specifies the
sequence of amino acids in a particular protein
Gene
Base + Sugar =
Nucleoside
Base + Sugar + Phosphate =
Nucleotide
Nucleosides containing ribose are known as
ribonucleotides
Nucleosides containing deoxyribose are known as deoxyribonucleotides
deoxyribonucleotides
What are the 3 components of a nucleotide
Deoxyribose sugar, a phosphate group and a nitrogenous base
The nitrogen-containing rings of nucleotides
Nitrogenous Bases
What are the two categories of Nitrogenous Bases
Pyrimidines, Purines
have a six-membered pyrimidine ring
Cytosine, Thymine, Uracil (for RNA)
Pyrimidines
Bear a second, five-membered ring fused to the six-membered ring
Adenine, Guanine
Purines
What is the proper base pairing for DNA
A pairs with T
G pairs with C
What is the proper base pairing for RNA
A pairs with U
G pairs with C
what bonds hold the base pairs together
Hydrogen bonds
bonds formed between the deoxyribose sugars and the phosphates
Phosphodiester bonds
Nucleotides are joined into chains
This creates a continuous sugar-phosphate
backbone.
Polynucleotide Chain
has a free phosphate group
5’ end
has a free hydroxyl group
3’ end
The two strands are oriented with opposite
polarities- that is they run antiparallel from each
other this is also known as
antiparallelism
The twisting of the two strands together creates a
wider gap called
the major groove
the narrower gap of two strands is called
the minor groove
important binding sites for CHONS that maintain DNA and regulate gene activity
grooves
thread-like structures inside the nucleus of a cell where DNA is packaged
Chromosomes
segments of DNA that contain the instructions for making a particular protein
Genes
large excess interspersed DNA
junk DNA
the bead part of chromatin
nucleosome
- The first and most fundamental level of chromatin
packing
*contains:
1. Core particle
2. Linker DNA
Nucleosome
Links nucleosome core particles
Linker DNA
DNA strand (147 nucleotides long) wrapped around a protein core of histone octamer
(composed of 8 histone proteins)
Core Particle
helps pull nucleosomes together and pack them into a more compact chromatin fiber
Histone H1
brings together parts of the DNA sequence within the same long DNA molecule to form the overall “loop-ome” structure
CTCF
protein machines that use the energy
of ATP hydrolysis to change the position of the DNA wrapped around nucleosomes, making the DNA either more accessible or less accessible to other proteins in the cell
Chromatin-remodeling complexes
- the most highly condensed form of interphase chromatin
- about 10% of an interphase chromosome
- concentrated around the centromere region and in the telomeres
Heterochromatin
- Has more decondensed state than heterochromatin
Euchromatin
- Aggregate of DNA and histone proteins
- Makes up a eukaryotic chromosome
Chromatin
- Longitudinal subunit produced by chromosome
replication
Chromatid
- AKA primary constriction
- Constricted non-staining portion of a chromosome
Centromere
- Tip of a chromosome
- Contains a DNA sequence required for stability of
chromosome ends
Telomere
- Short arm of the chromosome
- p for “petite”
p arm
- Long arm of the chromosome
- q for “not-p” or queue (french for tail)
q arm
- Centromere is at the center
- Both arms are of equal length
Metacentric
- Centromere is slightly offset from the center
- Both arms are slightly asymmetrical
Submetacentric
- Centromere is severely offset from the center
- One very long and one very short arm
Acrocentric
- Centromere is at the very end of the chromosome
- Doesn’t exist in humans
Telocentric
- lacks a centromere
Acentric
- has 2 centromeres
Dicentric
permit smaller segments of each chromosome arm to be identified
* The cytogenetic bands count from the
centromere out toward the telomeres
G-bands
- Process by which a copy of a DNA molecule is made
- Must occur before cell can divide to produce 2 identical daughter cells
- Produces two complete double helices from the original DNA molecule
- Duplication rate is as high as 1000 nucleotides/second
DNA Replication
the parent DNA molecule remains intact after being copied and the daughter molecule would contain two entirely new
DNA
Conservative
DNA replication proceeds through a series of breaks and reunions; the resulting copies would be patchwork collections of old and new DNA
Dispersive
Each parent strand serves as a template for the synthesis of a new daughter strand; the resulting helices each contains one strand from the original parent in addition to one newly synthesized strand
Semi-conservative
3 steps of DNA replication
Initiation, Elongation, Termination
pries the 2 DNA strands apart, breaking the hydrogen bonds between the bases
DNA Helicase
Y-shaped junctions where DNA synthesis occurs
Replication forks
prevent the separated strands from re-forming base pairs
Single-strand DNA-binding proteins
catalyzes the addition of nucleotides to a growing DNA strand using the original parent strand as template
DNA polymerase
is made up of a short chain of RNA that serves as a starting point for DNA polymerase
Primer
is an RNA polymerase that synthesizes the RNA primer
Primase
- Strand that grows in the normal 5’ to 3’ direction
- DNA strand is synthesized continuously
- RNA primer is needed only to start replication at a replication origin
Leading strand
- Strand that appears to grow in the incorrect 3ʹ-to 5ʹ direction
- Backstitching imparts slight delay to the synthesis
Lagging strand
DNA is made discontinuously in successive, separate, small pieces of DNA called
Okazaki fragments
– Degrades RNA
Nuclease
– Replaces the degraded RNA with DNA
Repair polymerase
– Joins one DNA fragment to adjacent DNA fragment
DNA ligase
– Relieves tension on the other side of the replication fork made from the unwinding of the replication fork
DNA topoisomerases
– keeps DNA polymerase firmly attached to the template while it is synthesizing new strands of DNA
Sliding Clamp
– Facilitates assembly of sliding clamp around DNA
Clamp loader
A purine base from a nucleotide is removed giving rise to lesions that resemble missing teeth
Depurination
Spontaneous loss of an amino group from a
cytosine in DNA to produce the base uracil
Deamination
promotes covalent linkage between two adjacent pyrimidine bases
UV Radiation
- “Clean” the broken ends and rejoin them by DNA ligation.
- Rapidly repairs the damage but nucleotides are often lost at the site of repair
Nonhomologous end joining
- Flawless repair of the double-strand break, with no loss of genetic information
- Most handy DNA repair mechanism available to the cell
Homologous Recombination
