biochem nucleutides, nucleic acids and heredity Flashcards
that the transmission of hereditary information took place in the nucleus, more specifically in structures called
chromosomes.
Chemical analysis of nuclei showed chromosomes are made up largely of proteins called
histones and nucleic acids.
The hereditary information was thought to reside in genes within the
chromosomes
By the 1940s, it became clear that ____carry the hereditary information
deoxyribonucleic acids (DNA
There are two kinds of nucleic acids in cells:
- ribonucleic acids (RNA)
- deoxyribonucleic acids (DNA)
*Purine
-Adenine (A)
-Guanine (G)
Both RNA and DNA are polymers built from monomers called
nucleotides.
- There are two kinds of nucleic acids in cells:
- ribonucleic acids (RNA)
- deoxyribonucleic acids (DNA)
*Pyrimidine
-Cytosine (C)
-Thymine (T)
-Uracil (U)
- A nucleotide is composed of
: a base, a monosaccharide, and a phosphate.
Nucleosides: composed of
base and monosaccharide
: a compound that consists of D-ribose or 2-deoxy-D-ribose bonded to a purine or pyrimidine base by a B-N glycosidic bond.
- Nucleoside:
is esterified with an -OH of the monosaccharide
a nucleoside in which a molecule of phosphoric
a nucleoside in which a molecule of phosphoric
esterified with an -OH of the monosaccharide
-a nucleoside in which a molecule of phosphoric acid is esterified with an -OH of the monosaccharide, most commonly either the
3’ or the 5’-OH.
base sequence is read from the
5’ end to the 3’ end
serves as a common currency into which energy gained from food is converted and stored.
adenosine 5’-triphosphate (ATP)
: the ordered arrangement of nucleic acid strands.
Secondary structure
a type of 2° structure of DNA in which two polynucleotide strands are coiled around each other in a screw-like fashion.
- Double helix:
DNA is coiled around proteins called
histones.
Histones are rich in these basic amino acids
Lys and Arg
Lys and Arg
whose side chains have a positive charge.
The negatively-charged DNA molecules and positively-charged histones attract each other and form units called
nucleosomes
Nucleosomes are further condensed into
chromatin.
a core of eight histone molecules around which the DNA helix is wrapped
Nucleosome
Chromatin fibers are organized into
loops
DNA bases are
A, G, C,
. Chromatin fibers are organized into loops, and the loops into the bands that provide the superstructure of
chromosomes.
The sugar in DNA is
2-deoxy-D-ribose
T; the RNA bases are
A, G, C, and U
- The three differences in structure between DNA and RNA are:
- The three differences in structure between DNA and RNA are:
- DNA bases are A, G, C, and T; the RNA bases are A, G, C, and U.
- The sugar in DNA is 2-deoxy-D-ribose; in RNA it is D-ribose.
- DNA is always double stranded; there are several kinds of RNA, all of which are single-stranded.
The sugar in RNA is
D-ribose.
DNA is always _____ stranded
double
Small Transports amino acids
Transfer RNA (tRNA)
RNA is always _____ stranded
single
Directs amino sequence of proteins
Messenger RNA(mRNA)-
Combines with proteins to form ribosomes, the site of protein synthesis.
Ribosomal RNA(rRNA)
Pocesses intitial mRNA to its mature form in eukaryotes.
Small Nuclear RNA(snRNA)
Affects gene expression; used by scientists to knock out gene being studied.
Small Inefering RNA(siRNA)
Affects gene expressions; important in growth and development
Micro RNA (miRNA)
a section of DNA that, when transcribed, codes for a protein or RNA.
- Exon
catalyze cleavage of part of their own sequences in mRNA and tRNA
Ribozymes (catalytic RNA)
: a section of DNA or mRNA that does not code for a protein.
Intron
a segment of DNA that carries a base sequence that directs the synthesis of a particular protein, tRNA, or mRNA
Gene:
In bacteria the gene is
continuous
. In higher organisms the gene is
discontinuous.
. DNA double helix unwinds at a specific point called an
origin of replication
______chains are synthesized in both directions from the origin of replication
- Polynucleotide
At each origin of replication, there are
two replication forks
At each origin of replication, there are two replication forks, points at which new _______ strands are formed.
polynucleotide
- DNA is synthesized from its
5’ > 3’ end (from the 3’ -> 5’ direction of the template).
- The leading strand is synthesized continuously in the
5’ ->
The lagging strand is synthesized semidiscontinuously as a series of
Okazaki fragments
Okazaki fragments of the lagging strand are joined by the
enzyme DNA ligase.
___-direction toward the replication fork.
3
Unwinds the DNA double helix/ unzips enzyme
Helicase-
During replication, the very condensed superstructure of chromosomes is opened by a
signal transduction mechanism
(also called gyrases) facilitate the relaxation of supercoiled DNA by introducing either single strand or double strand breaks in the DNA.
Tropoisomerases
- are assemblies of “enzyme factories”.
Replisomes
Replication is ______
semiconservative
Replication is semiconservative
each daughter strand contains one template strand and one newly synthesized strand
Joins assembled nucleotides
DNA Polymerase
Threads leading strand
Clamp Proteins-
removes a positive charge and thus weakens the DNA-histone interactions.
Acetylation
Synthesizes primers
Primase
Joins Okazaki fragments in lagging strand
Ligase
Replication of DNA starts with unwinding of the
double helix.
signal transduction mechanism.
* One step of this mechanism involves
acetylation and deacetylation of key lysine residues
Unwinding proteins called _______attach themselves to one DNA strand and cause separation of the double helix.
helicases
are placed at about every 50 nucleotides in the lagging strand synthesis.
Primases
are enzymes that catalyze the synthesis of primers
- Primases
one of the most common repair mechanisms.
Base excision repair (BER)
An ______ liberates the sugar-phosphate unit of the damaged site
exonuclease
are key enzymes in replication.
- DNA polymerases
seals the backbone to complete the repair
DNA ligase
an _______ catalyzes the hydrolysis of the backbone
endonuclease
It catalyzes the hydrolysis of the -N-glycosidic bond between the incorrect base and its deoxyribose.
DNA glycosylase
inserts the correct nucleotide
- DNA polymerase
removes and repairs up to 24-32 units by a similar mechanism involving a number of repair enzymes
NER (nucleotide excision repair
a genetically identical population.
Clone
a process whereby DNA is amplified by inserting it into a host and having the host replicate it along with the host’s own DNA.
- Cloning
an automated technique for amplifying DNA using a heat-stable DNA polymerase from a thermophilic bacterium.
Polymerase chain reaction (PCR)
