Studied by 9 peoplewhat are chromosones wrapped around?
a protein called histones
Erwin Chargaff (1950)
developed chargaff’s rules, he stated that the bases of DNA were paired together in a specific order
what are the pairs of DNA bases
Adenine and thymine | cytosine and Guanine
what is the purpose of chargaff’s rules?
to find the amount of each base in a DNA sample because if you know one you can find the rest
example on how to use chargaff’s rules:
if Adenine is 16% of a sample then so is Thymine. Those together make 32% of the sample. Subtract 32 from 100 (because it is the total of the sample) to find the total of Guanine and Cytosine. divide 68% by 2 to find the amount of Guanine and Cytosine (34%).
Rosalind Franklin (1951)
a British female scientist who made a huge contribution to the study of DNA by establishing that DNA was the shape of a douple helix in a X-ray diffraction
what was the significance of that X-ray Rosalind Franklin took?
it was taken in 1952 and is the most famous c-ray image of DNA. it took 100 hours to get the image and the calculations took 1 year to analyze. Watson and Crick saw this and were inspired to build a structure based on it.
James Watson and Francis Crick (1953)
they created the first accurate DNA model with the help of Chargaff and Franklin’s research
what was the structure Watson and Crick made?
it was a double helix which consisted of subunits called nucleotides and the sides were a phosphate backbone and alternating sugars
what does a nucleotide consist of?
a 5-carbon sugar (deoxyribose), a phosphate, and a nitrogen base (A, T, C, G)
what are hydrogen bonds for in DNA
hydrogen bonds hold the two sides together and twists it into the Double Helix shape. these are also easy to break, so the two sides of DNA are easy to separate during replication
what were watson and crick awarded for their work?
a nobel prize in 1962
Frederick Griffith
using streptococcus, he searched for a vaccine, but he noticed between the 2 types he used that one had a capsule and other’s did not
what else did Frederick Griffith do after his discovery between the two streptococcus?
he injected the two types of stuff (bacteria/strep) into mice. The mice that were injected with the encapsulated bacteria died when the others didnt, but when the encapsulated bacteria was injected using heat the mice didnt die. when the mice were injected with both they caught pneumonia and died.
what is DNA like in a prokaryotic cell?
nucleoid
what is primary structure in proteins?
a polypeptide chain
what is a protein’s secondary structure?
A shape is formed due to interactions with other amino acids (a-helix and the b-sheet)
what is tertiary structure in proteins?
the three dimensional shape of proteins. the folded polypeptide chain
what is quatarnary structure?
when proteins consist of two or more chains of polypeptide.
what is RNA?
a mirror copy of a segment of DNA (a gene) which is then delivered to the ribosome to be converted into a protein
what does the order of bases on an RNA strand determine?
the order of amino acids that will build certain proteins
what are the 3 types of RNA
mRNA (messenger), rRNA (ribosome), tRNA (translate)
What is the difference between DNA and RNA
in RNA thymine is replaced by Uracil (allows RNA to leave nucleus due to structure.)
what is the process of gene expression/protein synthesis?
transcription and translation
what is gene expression for?
to activate a gene (or transcribe DNA to get mRNA) that results in amino acid chains (polypeptides). These will eventually form into proteins through protein structure
What is DNA replication?
the process by which DNA makes a copy of itself.
what is semi conservative, and why is DNA replication considered this
half of the original DNA is still on the replicated DNA. This is because this half for the replicated DNA is considered the “template strand” to determine the complementary bases
There are multiple replication forks in DNA replication, why?
It would take forever to go from one end to the other, it is more efficient to open up several points at one time.
How many hydrogen bonds are in between A and T
2
How many hydrogen bonds are in between C and G
3
how many chromosones does a human diploid have? what about a halpoid?
diploid: 46
halpoid: 23
which base pairs are purines and why?
adenine and guanine are because they are larger
which base pairs are pyrimidines and why?
thymine and cytosine are because they are smaller
What was Watson and Crick’s original idea of a DNA structure?
triple helix, the phosphates were on the inside
what are the 4 main enzymes during DNA replication?
DNA polymerase, helicase, primase, and ligase
what does helicase do?
the “unzipping enzyme” which separates the DNA
what does DNA polymerase do?
the “builder” enzyme which puts DNA bases together
what does primase do?
the “the initializer” which primes areas to tell DNA polymerase where to work
what does ligase do?
“the gluer",” glues okazaki DNA fragments together
what is the origin in DNA replication?
where helicase rips through the DNA (the middle)
what is supercoiling in DNA?
the DNA coild too tightly together when being unwinded by helicase. This stops any new replication
why does the order of the bases on the RNA strand important?
it determines the order of amino acids that will build certain proteins. every 3 nucleotide is one codon that tRNA will code for a certain amino acid
what are the steps to DNA replication (simplied)?
helicase unwinds DNA and makes a replication fork, primase guides the DNA polymerase on where to add complementary bases.
Why are there 5’ 3’ and 5’ 3’ strands in DNA
because DNA runs antiparrallel, so one side is upside down causing the third carbon to be above the fifth on the sugar molecule.
explain 3’ to 5’ and 5’ to 3’ in depth
this is what is considered by which way the carbons are placed in a nucleotide in DNA. If the oxygen in deoxyribose is facing upwards, the fifth carbon is above the third, so this means this strand is the leading strand. The opposite is true for the lagging strand (3’ to 5’)
explain the first part of DNA replication (in depth)
the helicase rips upwards through the original DNA. This leads to different strands (remember that one is 5’ 3’ (up) and the other is upside down or 3’ 5’). primase tells DNA polymerase where to build on each strand. Note that DNA polymerase can only build up (5’ to 3’) and it will “chase” the fifth carbon on deoxyribose, starting from the third carbon, to add new nucleotides to the template strand. This will be the leading strand because polymerase follows the helicase through the DNA
Now explain the lagging strand during DNA replication (or second part)
On the lagging strand, or 3’ 5’ strand, DNA polymerase has to build in the opposite direction than the other side, but helicase is still going upwards (so polymerase has so flip and build down while helicase is still going up). This means that DNA polymerase and primase do not follow helicase since they go in opposite directions, so each time helicase brings down more DNA for the template strand polymerase and primase have to jump backwards on the lagging strand to continue adding new nucleotides
explain why there are fragments on the lagging strand during DNA replication
when DNA polymerase and primase keep jumping back up over and over and this leaves little gaps in between the new sections that polymerase just added nucleotides to. These fragments are called Okazaki fragments and the enzyme ligase fills in these spots so RNA does not.
what is a codon in protein synthesis.
A codon is a triplet of nucleotides on mRNA and is read by the rRNA.
what is an anticodon in protein synthesis
an anticodon are the nucleotides opposite of a codon and is on the bottom of tRNA like three little feet. This tells tRNA which amino acid to find in the cytoplasm
what is the purpose of anti codons and codons during protein synthesis
these two work together to determine the order of amino acids on a polypeptide chain. These are needed so the tRNA and mRNA can bond together during protein synthesis to leave behind the designated amino acid on rRNA.
is there a certain codon that has to be the start of an amino acid chain for rRNA and tRNA? if so which one and what is the anticodon and amino acid
yes: for mRNA to start being read by rRNA, the first codon must ALWAYS be “AUG.” The anticodon on tRNA is UAC which brings the amino acid “met” to start the polypeptide
What are the steps of transcription during protein synthesis?
mRNA is made by adding the complementary nucleotides from a template strand from DNA (remember that T is now U in mRNA, this is so mRNA can leave the nucleus). mRNA now goes outside of the nucleus to the rough ER. the rough ER has rRNA (ribosomes) on it where mRNA can be translated/coded for certain amino acids
what are the steps of translation during protein synthesis?
rRNA reads a codon from mRNA, it then calls for a specified tRNA, and this tRNA brings a certain amino acid. The tRNA leaves and an amino acid is left behind
what is the main purpose of having both all three RNA’s?
the mRNA tells rRNA which amino acid is needed for the polypeptide chain. rRNA calls for a tRNA based on the anticodon for whichever codon it just read, and tRNA brings the desired amino acid
what is gene regulation?
this controls gene expression/protein synthesis (specifically transcription) with enzymes. It controls which genes are expressed, how fast they are expressed, and when to stop the expression. so in simpler terms, it is the regulation of making RNA.
what are the different enzymes included in gene expression?
promoter, operator, repressor
what is an operon?
this is the part of DNA where the enzymes are regulating protein synthesis. this includes multiple genes that will be synthesized and the enzymes that regulate the synthezation
what is a promoter during gene regulation?
instead of primase, like during DNA replication, there is a promoter to tell RNA polymerase where to start building
what is an operator during gene regulation?
this is where a repressor can bind and block RNA polymerase from making RNA
what is a repressor during gene regulation?
this enzyme binds with an operator and blocks RNA polymerase, but if something binds with this it will move and RNA polymerase can continue making RNA.
What are mutations and how are they caused?
mutations are when nucleotides are changed, deleted, or added in DNA. These are caused by mutagens
what are mutagens? list them
these are any physical or chemical agents that change DNA sequences. These can improve, harm, or not change anything in the cell. UV, cigarette smoke, alcohol in excess, viruses, car exhaust, chemicals.
what is a deletion mutation?
a base is left out.
EX: og. ATCG new. ACG
What is a insertion mutation?
a base is added
EX. og. ATCG new. ATTCG
what is a substitution mutation?
A base is changed and switched out for another
EX. og. ATCG new. AGCG
what is a translocation mutation?
part of a chromosone breaks off and attaches to another
EX. og. ATCG new. (strand 1) ACG (strand 2) ATTCG
what is a duplication mutation?
a base is duplicated
EX. og. ATCG new. ACCG
what is an inversion mutation?
the order of bases are reversed
EX. og. ATCG new. GCTA
what is a point mutation?
substitute one base for another
EX. og. ATCG new. AGCG
what is a frameshift mutation?
a base is either added or removed in a gene and this causes the whole
EX. og. ATCG new. ATG…ACG
what is a silent mutation?
when a base in a codon changes, but the codon still codes for the exact same amino acid.
EX. og. AGC new. AGU
what is a nonsense mutation?
a base in a codon changes to code for a “stop” amino acid
EX. og. UGU. new. UGA
Who are Hershey and Chase and what was their importance in the development of knowledge about DNA?
they tested DNA to see if it was made out of sugar or protein. They used radioactive phosphorus test for sugar and radioactive sulfur for protein. The radioactive phosphorus broke down the DNA so they determined that it was deoxyribose in the backbone of DNA
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