Chapter 4 - DNA, RNA, and the flow of genetic material Flashcards
DNA and RNA are long linear polymers called
nucleic acids.
mRNA
The information-carrying intermediates in protein synthesis.
Introns
a segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.
Exons
a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
Each monomer unit within the polymer of DNA and RNA is a
nucleotide.
A single nucleotide consists of three components:
A sugar, a phosphate, and one of four bases.
RNA and DNA differ in
the sugar component and one of the bases.
In deoxyribose, which carbon lacks an oxygen atom that is included in ribose?
2
Sugar carbons are numbered with primes to
differentiate them from atoms in the bases.
The sugars in both nucleic acids are linked to one another by
phophodiester bridges.
DNA bases that are derivatives of purine.
adenine and guanine
DNA bases that are derivatives of pyrimidine.
cytosine and thymine
In RNA, one of the four major bases is ______ instead of ______.
uracil; thymine
Each phosphodiester bridge has a ______ charge.
negative
Nucleoside
A unit consisting of a base bonded to a sugar.
4 nucleosides in RNA
adenosine, guanosine, cytidine, and uridine
4 nucleosides in DNA
deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine
A nucleotide is a
nucleoside joined to one or more phosphoryl groups by an ester linkage.
The monomers linked together to form the building blocks in DNA and RNA are
nucleotide triphosphates.
The four nucleotides that link to form DNA are monophosphates called
deoxyadenylate, deoxyguanylate, deoxycytidylate, and thymidylate.
The four nucleotides that link to form RNA are monophosphates called
adenylate, guanylate, cytidylate, and uridylate.
A DNA chain has directionality, commonly called
polarity.
The human genome comprises approximately ________ nucleotides in each strand of DNA.
3 billion
The nucleotides in the human genome are divided into distinct molecules of DNA called
chromosomes.
The double helix in DNA is stabilized by
hydrogen bonds and van der Waals interactions.
In DNA, adjacent bases are separated by approximately
3.4 Angstoms.
In DNA, there are approximately _______ bases per turn.
10.4
The diameter of the DNA helix is about
20 Angstroms.
Stem-loops are created when
two complementary sequences within a single strand come together to form double-helical structures.
The sequence of bases of one strand of the double helix in DNA precisely determines
the sequence of the other strand.
Semiconservative replication
the process by which DNA makes copies of itself, each strand, as it separates, synthesizing a complementary strand.
The dissociation of the double helix is called
melting.
The melting temperature (Tm) of DNA is the temperature at which
half the helical structure is lost.
Hypochromism
Stacked bases in nucleic acids absorb less ultraviolet light than do unstacked bases.
Annealing
Separated complementary strands of nucleic acids spontaneously reassociate to form a double helix when the temperature is lowered below Tm
DNA polymerases
catalyze the step-by-step addition of deoxyribonucleotide units to a DNA strand.
DNA replication has an error rate of less than
10-8 per base pair.
The information stored in DNA becomes useful when it is expressed in
the production of RNA and proteins.
Messenger RNA (mRNA) is
the template for protein synthesis or translation.
Transfer RNA (tRNA)
carries amino acids in an activated form to the ribosome for peptide-bond formation.
Ribosomal RNA (rRNA) is the major component of
ribosomes.
In prokaryotes, there are three kinds of rRNA
23S, 16S, and 5S
Abundance of types of RNA
rRNA > tRNA > mRNA
All cellular RNA is synthesized by
RNA polymerases.
Transcription
The synthesis of RNA from a DNA template.
RNA polymerase requires what 3 components?
- A template
- Activated precursors
- A divalent metal ion
Transcription begins near
promoter sites.
Transcription ends at
terminator sites.
Discrete start and stop signals for transcription are encoded in
the DNA template.
The adapters in protein synthesis are
transfer RNAs.
tRNAs contain what two sites.
- amino acid-attachment
- template-recognition
How many nucleotides encode an amino acid?
3
Synonyms
Codons that specify the same amino acid.
Degeneracy of the genetic code minimizes
the deleterious effects of mutations.
Codons representing chain termination
UAA, UAG, and UGA
Spliceosomes
Assemblies of proteins and small RNA molecules that carry out splicing.
Nascent
having recently come into existence.
Translation
The synthesis of a protein from an RNA template.
