DNA, RNA, and Proteins Flashcards
what did Friedrich Mieschner do?
discovered nuclein by isolating phosphate-rich chemicals from the nuclei of white blood cells in pus
what 2 experiments proved DNA to be the hereditary material?
Avery’s transformed infectious bacteria, Hershey and Chase’s injection of DNA into a host cell to make new viruses
what 3 experiments on bacterial transformation proved DNA to be the substance of genes?
- Griffith
- Avery, MacLeod, and McCarty
- Hershey and Chase
describe the Griffith experiment
- took 2 types of bacteria; virulent (s) and nonvirulent (r)
- (s) kills mice, (r) does not
- (s) mutates to (r) form, does not kill mice anymore
- (s) heated, doesn’t kill
- heat-killed (s) revived by combining with (r), kills mice, and living (s) form found in autopsy
describe the Avery, MacLeod, and McCarty experiment
took Griffith further
- took living (r) form, combined with heat-killed (s) form in a medium, over time found only living (s) form
- added protease, RNase, and used ultracentrifguation, but still found living (s) form
- added DNase, (s) not found, showing that DNA is dominant
describe the Hershey and Chase experiment
provided convincing evidence that DNA is the genetic material
-bacteria injected with their phage would replicate only the changed phage DNA
what is Chargaff’s rule?
the ratios of A and T are 1:1, and the ratios of G and C are 1:1
when did Watson and Crick propose their double helix model?
1953
what did Rosalind Franklin do?
photographed DNA molecule using X-ray crystallogrophy
what did Franklin’s DNA picture show?
that DNA is a coil with a constant diameter of 2nm
what is the blueprint for all life?
DNA, deoxyribonucleic acid
and is a karyotype?
a picture of all an organisms’ chromosomes
how many chromosomes does a human have?
46
how many chromosomes does a dog have?
78
how many chromosomes does a cat have?
38
how many chromosomes do cattle have?
60
how many chromosomes does a goat have?
60
how many chromosomes does a sheep have?
54
how many chromosomes does a horse?
64
how many chromosomes does a donkey have?
62
how many chromosomes does a chicken have?
78
how many chromosomes does a turkey have?
80
how many chromosomes do camels, alpaca, and llamas have?
74
how many chromosomes does a rabbit have?
40
how many chromosomes does a rat have?
38
DNA is a polymer of?
nucleotides
each nucleotide is composed of?
- 5-carbon sugar
- phosphate
- nitrogenous base
list the 4 nitrogenous bases?
- adenine
- thymine
- guanine
- cytosine
list the purine bases (double ringed)
- adenine
2. guanine
list the pyrimidine bases (single ringed)
- cytosine
2. thymine
adenine pairs with thymine in what kind of bond?
double
cytosine pairs with guanine in what kind of bond?
triple
in DNA replication, nucleotides come together to make a new strand that is ____ to the old strand?
complimentary
the new double strand formed in DNA replication is a ____ to the old double strand?
duplicate
how is DNA replicated?
semi-conservative replication
is there only one form of the DNA double helix?
no, it can assume alternative forms
in what 4 organisms are DNA molecules circular instead of linear?
- prokaryotes
- mitochondria
- chloroplasts
- viruses
what kind of viruses carry single-stranded DNA?
bacteriophages
what virus carries RNA?
AIDS
list the 4 requirements for DNA to be the genetic material
- must carry information
- must replicate
- must allow for information to change, or mutate
- must govern the expression of the phenotype
where does DNA replication take place?
in the nucleus
what produces semiconservative replication?
complimentary base pairing
in DNA replication, what happens to the double helix?
it unwinds and each strand acts as a template
what does complimentary base pairing ensure?
that T signals the addition of A on new strand, and G signals addition of C
how many daughter helices are produced after replication?
2
in replication, what does Pol III do?
produces new strands of complimentary DNA
in replication, what does Pol I do?
fills in gaps between newly synthesized Okazaki fragments
in replication, what does DNA helicase do?
unwinds double helix
in replication, what do single stranded binding proteins do?
keep helix open- the exact opposite of bind actually
in replication, what does primase do?
creates RNA primers to initiate synthesis
in replication, what does ligase do?
welds together Okazaki fragments
where does DNA replication begin?
at the origin of replication
how many origins of replication are there?
can be multiple, up to 100,000 in complex organisms, but most bacteria only have 1
what is the replication bubble?
the area where DNA helices are unwound and replication takes place
what is the replication fork?
the active area where replication takes place
what establishes the RNA primers in replication?
primase
what holds open the unwound strands of DNA during replication?
single-stranded binding proteins
what joins Okazaki fragments into a continuous strand after the removal of primers in replication?
DNA ligase
what kind of replication occurs on the leading strand?
continuous
what kind of replication occurs on the lagging strand?
discontinuous
what direction does replication move in?
bidirectional, the replication forks move in opposite directions
what do telomeres do in linear chromosomes during replication?
ensure the maintenance and accurate replication of chromosome ends
how many origins of replication are in circular chromosomes, such as E. coli?
only one
what can unwinding and replication do to circular chromosomes, and what problems may that cause?
supercoiling, which may impede replication
what is topoisomerase?
an enzyme that relaxes supercoils by nicking strands
what is the basis for repair of errors that occur during replication or storage?
redundancy, more than one codon can code for the same amino acid
are errors during replication common?
no, they’re rare
what is recombination?
when homologs physically break, exchange parts, and rejoin, creating reciprocal products
where can recombination occur?
anywhere along the DNA molecule
what prevents mutations from occurring during the recombination process?
precision in the exchange of genetic information
what does the Watson-Crick model show?
that DNA is a double helix composed of 2 antiparallel strands of nucleotides
in what order does DNA carry information?
in the sequence of its bases
list the 5 steps of DNA replication, including enzyme function
- helicases unwind the parental double helix
- single-stranded binding proteins stabilize the unwound parental DNA
- the leading strand in synthesized continuously in the 5’ to 3’ direction by DNA polymerase
- the lagging strand is synthesized discontinuously. Primase synthesizes a short RNA primer, which is extended by DNA polymerase to form an Okazaki fragment
- After the RNA primer is replaced by DNA, DNA ligase joins the Okazaki fragment to the growing strand
what does RNA stand for?
ribonucleic acid
how is RNA similar to DNA
it has repeating subunits, nucleotides
what are the 4 main differences between RNA and DNA?
- RNA contains ribose instead of deoxyribose in its nucleotides
- adenine pairs with uracil instead of thymine like DNA
- RNA is single stranded and shorter
- RNA is less stable than DNA, and doesn’t persist in the cell for very long, whereas DNA can persist for the life of the cell
what is the central dogma of molecular biology?
DNA to RNA: transcription
RNA to proteins: translation
what are the 3 different RNA molecules involved in protein synthesis?
- mRNA
- rRNA
- tRNA
what is transcription?
RNA synthesis from DNA
where does transcription occur?
in the nucleus
where does mRNA carry the message about what type of protein to make?
from the DNA in the nucleus to the ribosome outside the nucleus
what is the only difference between the transcribed RNa sequence from the DNA sequence?
the RNA sequence contains uracil instead of thymine
how is mRNA synthesized from DNA?
base pairing
how does DNA unwind?
in sections
what does RNA polymerase do in transcription?
attaches at the promoter sequence of DNA and moves along the DNA, unzipping the strands, allowing for more mRNA molecules to be formed
what is formed during transcription as a complimentary copy of a region one on strand of the DNA molecule?
a molecule of messenger RNA
list and describe the 3 modifications that initial mRNA goes through before leaving the nucleus?
- capping: addition of a 7 methylguanosine cap on the 5’ end prevents mRNA from degradation outside the nucleus
- poly-A tail: polyadenylation on the 3’ end stabilized mRNA
- intron splicing: removes the noncoding segments from the mRNA strand and leaves the exons, or coding segments to leave the nucleus
what is a codon?
each 3 consecutive bases on the mRNA is a code word, or codon, that specifies an amino acid
how many codons make up the genetic code?
64
what 3 codons act as signal terminators?
UGA, UAG, UAA
what codon codes for both methionine and is also the START signal for translation?
AUG (school starts in august)
how many amino acids are there in all life forms?
20
what are amino acids?
the bricks or building blocks that make all proteins
what is translation?
synthesizing a protein from amino acids according to the sequences of the nucleotides in mRNA
where does translation occur?
at the ribosome in the cytoplasm of the cell
what type of RNA is needed for protein synthesis?\ and what does it do?
rRNA, ribosomal RNA; helps mRNA bind to the SMALL subunit of the ribosome
what is tRNA?
transfer RNA; brings specific amino acids to the ribosome to be assembled as proteins, 80 nucleotides long
what does ribosomal RNA join with to make ribosomes?
a bunch of proteins
what is the site of protein synthesis?
ribosomes
what do ribosomes consist of?
a large subunit and a small subunit that mRNa binds to
list the 6 steps of translation
- mRNA leaves the nucleus and migrates to the ribosome
- mRNA binds to the SMALL ribosomal subunit
- tRNA brings an amino acid to the ribosome, where the anticodon on the tRNA binds to the codon of the mRNA
- the amino acid bonds to its adjoining amino acid to form a growing polypeptide molecule
- the tRNA without the amino acid is released from the ribosome
- other tRNA’s bring amino acids to the ribosome to complete the protein molecule
where does protein synthesis occur?
in the cytoplasm of the cell
what are the repeating subunits of protein molecules?
amino acids
why is the order of amino acids important?
it determines the 3D shape of the molecule, and the protein function
what are mutations?
changes in the DNA sequence that may be passed along to future generations; not always bad
what are point mutations?
a single base substitution
what are frame-shift mutations?
modifications of the reading frame after a deletion or insertion, resulting in all codons downstream being different
what are the 2 types of frameshift mutations?
- deletion: a small DNA segment is lost
- insertion: a segment of DNA is added
both change the entire sequence