DNA, RNA, and Proteins Flashcards
What is the central dogma of genetics?
DNA–transcription–> RNA–translation–>Protein
What is the site of protein synthesis?
ribosomes
What did Friedrich Misescher do?
isolated phosphate-rich chemicals from nuclei of white blood cells in 1868 and called it nuclein
What is Nuclein known as today?
nucleic acid
What did Oswald Avery discover?
DNA taken from a bacterium, Streptococcus pneumonia, could make non-infectious bacteria become infectious
What did Alfred Hershey and Martha Chase discover?
To make new viruses, a bacteriophage virus is injected into DNA, NOT protein, in the new host
What experiments did Frederick Griffith do?
experiments with smooth (S), virulent strain Streptococcus pneumonia, and rough (R), non virulent strain
What did Oswald Avery, Colin MacLeod, and Maclyn McCarty discover?
DNA is the transformation material
bacterial transformation implicates ____ as the substance of ____.
Bacterial transformation implicates DNA as the substance of genes
What happened when the smooth strain was injected into the mouse?
death
What happened when the rough strain was injected into the mouse?
it lived
What happened when the dead smooth strain was injected into the mouse?
it lived
What happened when the dead smooth strain and the rough strain was injected into the mouse?
it died
How did the mouse die when injected with a rough strain and a dead smooth strain?
the rough strain was transformed by mixing it with the dead smooth strain
How did Avery, MacLeod, and McCarty do their experiment?
they replicated Griffith’s experiment and got the same results; then they added different enzymes to see if transformation would still occur; DNase was added and DNA was destroyed and the R cells remained R cells
What did Hershey and Chase conclude?
DNA is genetic material (transforming material)
What kind of experiment did Hershey and Chase do?
waring blender experiment using T2 bacteriophage and bacteria, used radioactive labels 32 P for DNA and 35 S for protein
How does bacteriophage infect bacteria?
it attached to it and injects it with DNA to make many copies of the virus, which are then released when the bacteria bursts
What was the warring blender used for?
to separate the bacteria from viruses attached to the outside
What were the results of the bacteriophage with 32 P labeled DNA?
radioactivity was discovered in the bacteria host and in the viruses made
What were the results of the bacteriophage with 35 S labeled protein?
radioactivity discovered in the bacteriophage ghosts on the outside
What did James Watson and Francis Crick discover?
DNA is a double helix
How did Watson and Crick come to their conclusion?
they learned about x-ray diffraction patterns projected by DNA, knowledge of chemical structure of nucleotides, Chargaff’s demonstrated that ratios of A to T and G to C are 1:1
Who suggested that DNA was a coil and double helix first?
Rosalind Franklin
What does DNA stand for?
Deoxyribonucleic acid
What is the blueprint for life?
DNA
How many chromosomes do humans have?
46
What is a gene?
a section of DNA that codes for a particular trait
Which sex chromosome has more genes?
X
What is DNA a polymer of?
nucleotides
What is each nucleotide composed of?
5-carbon sugar, phosphate, and nitrogen base
What are the 4 nitrogenous bases for DNA?
Adenine, Guanine, Cytosine, and Thymine
What does a purine look like?
2 blobs
What does a pyrimidine look like?
1 blob
What are the purines for DNA?
adenine and guinine
What are the pyrimidines for DNA?
Cytosine and Thymine
What does Adenine pair with? How many bonds?
Thymine; double
What does Cytosine pair with? How many bonds?
Guanine; triple
which bond is strongest, requires most heat to break?
triple
What is DNA’s structure?
double helix, coil
Where does DNA replication take place?
nucleus
What does each DNA strand become for replication?
a template
What is assembled on the DNA template?
proper base-pairs
What is connected together to make a new strand in DNA replication? What is the strand compared to the old strand?
nucleotides; complementary
When a new DNA strand is formed and connected to the old strand, what is this type of replication called?
semi-conservative
What is semi-conservative replication?
where one strand acts as a template and is old, and a new strand is formed
What happens when DNA is heated?
DNA double strands separate
What has circular DNA molecules?
prokaryotes, mitochondria, chloroplasts, viruses
What has single stranded DNA?
some viruses (bacteriophages)
What carries RNA instead of DNA?
some viruses (like AIDS))
What are the four requirements for DNA to be genetic material?
must carry information, must replicate, must allow for information to change, must govern the expression of the phenotype
What allows for information to change?
mutation
What governs the expression of the phenotype?
gene function
What is DNA replication?
copying genetic information for transmission to the next generation
What does complementary base pairing produce?
semiconservative replication
What is the function of polymerase III?
produces new strands of complementary DNA
What is the function of polymerase I?
fills in the gaps between newly synthesized Okazaki segments
What is the function of DNA helicase?
unwinds double helix
What is the function of single stranded binding proteins?
keep helix open
What is the function of primase?
creates RNA primers to initiate synthesis
What is the function of Ligase?
welds together Okazaki fragments
What direction does DNA replication occur in?
it is bidirectional
What way does the replication fork move?
in opposite directions
What is the function of telomeres in linear chromosomes?
ensure the maintenance and accurate replication of chromosome ends
What is the origin of replication like for circular chromosomes?
there is only one
What can happen to circular chromosomes if unwinding and replication occurs?
supercoiling, which can impede replication
What is the function of topoisomerase?
it is an enzyme that relaxes supercoils by nicking strands
What must cells ensure the accuracy of?
genetic information
How do cells keep genetic info accurate?
redundancy, enzymes repair chemical damage to DNA, and errors during replication are rare
What is redundancy?
the basis for repair or errors that occur during replication or during storage
Where can recombination events occur on the DNA?
anywhere along the DNA strand
What do homologs do?
physically break, exchange parts, and rejoin
What do breakage and repair do?
create reciprocal products of recombination
What does precision in the exchange do?
prevents mutations from occurring during the process
What can gene conversions result in?
unequal yield of two different alleles (from crossing over or from not?)
What is the universal genetic material?
DNA
What are the 5 steps of DNA replication?
- helicases unwind the parental double helix
- single-strand binding proteins stabilize the unwound parental DNA
- the leading strand is synthesized continuously in the 5’-3’ direction by DNA polymerase
- the lagging strand synthesized discontinuously . Prime synthesizes a short RNA primer which is extended by DNA polymerase to form an Okazaki fragment
- after the RNA primer is replaced by DNA (by another DNA polymerase), DNA ligase joins the Okazaki fragment to the growing strand
What does RNA stand for?
ribonucleic acid
How is RNA similar to DNA?
repeating subunits, nucleotides
How is RNA different than DNA?
each nucleotide contains a different sugar (ribose instead of deoxyribose), Bases are A, G, C, and U
What is RNA’s structure?
single strand and shorter
Is DNA or RNA more stable? What does this mean?
RNA is less stable; it does not last in the cell for long whereas DNA can last for the entire life of the cell
What RNA molecules are involves in protein synthesis?
mRNA, rRNA, and tRNA
What is transcription?
RNA synthesis from DNA
Where does transcription take place?
nucleus
What does mRNA do?
carries the message about what type of protein to make from the DNA in the nucleus to the ribosome
How does the nucleotide sequence compare between DNA and RNA?
it is the same, except in RNA uracil is used instead of thymine
What is mRNA synthesized from?
from DNA using base pairing
How does DNA unwind for transcription? (???)
in a section
What does RNA polymerase do?
attaches at the promoter sequence of DNA, and it moves along the DNA, unzipping the strands - allowing for one mRNA molecule to be formed
What is the mRNA?
a complementary copy of a region on one strand of a DNA molecule
What happens once mRNA is formed?
enzymes in the nucleus remove the introns and leave the exons
What are introns?
non-coding sequence
What are exons?
coding sequence
What are the 3 modifications of mRNA?
capping, polyadenylation, and intron splicing
What is capping?
the addition of 7-methylguanine cap at 5’ end to prevent degradation of mRNA
What is polyadenylation?
addition of a poly-A tail on 3’ end to prevent degradation of mRNA
What is intron splicing?
removal of introns
What is a codon?
3 consecutive bases on the mRNA which specify an amino acid
What does the genetic code consist of?
64 codons
What codons act as signal terminators?
UAA, UGA, UAG
What is the start codon? What else does it code for?
AUG, methionine
How many amino acids are there?
20
What are amino acids?
the building blocks to make 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 ribosomes, in cytoplasm of the cell
What is needed for protein synthesis? Why?
rRNA; helps mRNA bind to the ribosome
What does tRNA do?
it is a transport molecule that brings specific amino acids (codon) to the ribosome to be assembled as proteins
What do rRNA do?
joins with a number of proteins to form ribosomes
What are ribosomes?
the site of protein synthesis
What do ribosomes consist of?
a large subunit and a small subunit
What on the ribosome does mRNA bind to?
the small subunit
What is the structure of tRNA?
it is folded
What does the anticodon loop do?
carries anticodon to the codon on mRNA
Where does protein synthesis occur?
cytoplasm
What are amino acids?
the repeating sub-units of protein molecules
What does amino acid order determine?
the protein and 3-dimensional shape of the molecule
What does the structure of the protein determine?
function
What does the function (biological activity) of the protein depend on?
its 3-D structure
What are the steps of protein synthesis summarized?
- mRNA transcribed from DNA
- tRNA binds amino acids
- tRNA with amino acid bonds to ribosome
- growing peptide chain
- completed polypeptide chain
What type of mutations can occur?
point shift and frameshift
What is a mutation?
changes in the DNA sequence, that may be passed along to future generations
What are point mutations?
a single base substitution
What are frameshift mutations?
modifications of the reading frame after a deletion or insertion, resulting in all codons downstream being different
What are the types of frameshift mutations?
deletion and insertion
Are mutations bad?
not all are bad
Are mutations common?
no, errors are rare but they do happen
