what are nucleic acids?
Polymers composed on nucleotides
what is the bond between nucleotides called?
phosphodiester bond
whats the nucleotide phosphodiester bond?
its the bond btw the suger of 1 nucleotide and the phosphate of the next nucleotide( btw nucleotides in a single strand )
what bond holds a DOUBLE nucleotide together?
Hydrogen bond
what is the sugar In deoxyribose?
DNA
whats the sugar in ribose?
RNA
what are the 3 parts of a nucleotide?
nitrogen containing base(5), 5-c-sugar, and a phosphate group
what is the 3' c attached to?
a hydroxyl group
what is the 5' c attached to
a phosphate PO4 -3
what are the 5 bases found in nucleotides?
adenine, thymine, guanine, cytosine, uracil
which one of the bases found in nucleotides is found ONLY in DNA?
thymine
whihc one of the bases is only found in RNA?
Uracil
what is a purine?
has 2-n-ring
which nitrogenous bases found in nucleotides are purines?
adenine and guanine
what are pyrimadines?
thyhave 1-n-ring
which nitrogenous bases found in nucleotides are pyramidines?
thymine, uracil, and cytocine
Base pairing review
Adenine (A) bind with Thymine (T), or Uracile (U) in RNA
and Guanine(G) bind with Cytosine(C),
result of base pairing in nucleotide
2 double helix strands, also anti parallel ( upside down, opposite to eachother)
what does Chargoff's rule say
for every A there is a T, for every G there is a C. In a DNA strand the amount of A is always equal to the amount of T, and the amount of G is always equal to the amount of C.
If DNA strand is 16% A, how much is C?
34%
If T equals 27%, what is G?
23%
DNA structure
1. nucleotide- the building blocks AKA monomers which join together forming 2.a single DNA or RNA strand held together by phosphodiester bond.4. DNA associates with histone proteins this is called (chromosomes).5.genome
Histones
Acts as a spool. DNA wraps around them.
Nuceosome complex
DNA wrapped around histones
DNA abt a meter long
genome
all DNA, all genetic material in an organism
Euchromatin
the dna is losely wound arround the histone. Because its losely wound the DNA is accessable so can be use it to make proteins
heterochromatin
tightly wound around DNA so DNA is INACCESSIBLE
telomere
the ends of the chromosomes, a noncoding sequence of nucleotides.
DNA made of nucleotides at the very end of chromosome but they don't code anything
whats the difference between chromosome, and chromatin?
chromatin is DNA spread out throughout the nucleus. and chromosomes is condenced
how do DNA strands run together
antiparallel
If DNA sample is 9% thymine, what is Guanine?
41%
Semi-conservative replication
when DNA replicates, each new daughter molecule has 1 parental strand and 1 new strand
what is the purpose of the cell making another EXACT copy of DNA?
to make more cells
Daughter DNA
new strand from parental strand, and new strand from the 1st new strand
build a new strand
5' ATTGG 3'
3' TAACC 5'
3 major steps of DNA replication ( all occuring during S phase )
1. deciding where to start 2.seperate parent strand 3.make parent strand
several problems the cell needs to overcome
1. supercoiling 2. DNA polymerase 3. DNA polymerase cant ADD to 5'
supercoiling
seperating twisted strands
DNA polymerase
cant start from scratch. can only add to the 3' end of a pre-existing nucleotide chain. CANNOT create a new. DNA polymerase will take RNA nucleotides and polymerize them
what can DNA polymerase also NOT do
replicate ends of DNA (telomeres). this is called end replication problem which is ONLY in eukaryotic cells
deciding where to start ( 1st major step of DNA replication )
theres DNA sequences called origins of replication that start the process. Eukaryotes have multiple origins or replications.
At O of R a replication bubble forms. DNA seperates forming replication bubble
seperating parental strands ( 2nd step of DNA replication )
The first one, Helicase( unzips DNA ), seperates strands by breaking the H bonds btw base pairs. This requires ATP energy. single strand binding proteins which arent enzymes, bind to base pairs preventing hydrogen bonds from reforming
Topoisomerase- solves supercoiling problem by moving ahead of helicase of replication bubble and cuts the DNA like scissors, allows DNA to unwind and re-attaches the DNA
where does the energy to build DNA come from
dioxy nucleotide triphosphtes ( dNTPs ) they had deoxy sugar
DNA primase is a type of ...
RNA polymerase
RNA polymerase
Makes a short stretch of rna at begining of replication, giving dna polymerase a free hydroxyl group to add on to.
what happens when RNA primase gets removed and there's a gap leaving:
.........gap..........5'GGACTGAGCAT3'
theres no way to fill in gap, so DNA gets shorter and shorter with every replication event. So telomeres will be gone, and cell will not be able to divide anymore so cells get old and die
what does DNA polymerase use to add nucleotides to newly growing DNA strand
RNA as a primer
leading strand
newly growing strand whos 3’ end is pointed toward replication fork. synthesis of the leading strand is continuous
lagging strand
newly forming DNA strand whos 5’ end is pointed toward replication fork , synthesis of this lagging strand is discontinuous
okazaki fragments
pieces of the lagging strand
ligase stitches(5th enzyme)
connects okazaki fragments together
end replication
protects against cancer
Telomerase ( enzyme 6)
solves the replication problem. enzyme thats very active in the embryo so cells can divide many times. As we age level of telomerase decrease to almost nothing
telomerase adds to 3' end of DNA strand extending it...
the lagging strand with the gap from RNA primase is filled in by DNA polymerase liked by DNA ligase