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Intro to Molecular Genetics :warning: (Base Pairing :red_flag: (DNA is…
Intro to Molecular Genetics
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Central Dogma
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The central dogma of molecular biology= DNA contains instructions for making a protein, witch are then copied by RNA
RNA
a small molecule that can sqeeze through pores in the nuclear membrane and carries the information from DNA in the nucleus to a ribosome in the cytoplasm and helps stable protien
DNA-RNA-Protein
Central Dogma of Molecular Biology: sequence of event
2 processes in central dogma= transcription and translation
uses instructions to make a protein
DNA
in eukaryotic cells chromosomes are in nucleus but proteins are made at chromosomes in the cytoplasm
contain instructions for all protein in body and found in chromosomes
Proteins
determine the structure and function of all cells
Protein structure: amino acids make up proteins and are encoded in DNA
Base Pairing
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Rule 1: the number of guanine units approximately= the number of cytosine units and the # of adenine units approximarely= the # of thymine units
Rule 2: the composition of DNA varied from one species to another
Chargaff's rules
Base paring rule:
A always pairs with T and G always pairs with C
DNA is composed of nucleotides, each of which contain a nitrigen-containg base, a five-carbon sugar(deoxyribose, and phosphate group). All nucleotides with one of four bases: adenine(A), guanine(G), cytosine(C), thymine (T)
Adenine and guanine= purine base(two rings) and cytosine and thymine= pyrimidine bases(one ring)
DNA Replication
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process were a cell's DNA is copies
strands of double helix serve as template for synthesis of a new stand, the two resulting double helices (one old and one new strand if DNA) are identical to initial double helix=
semi-conservative
occurs during Synthesis (S) phase of the eukaryotic cell cycle
semi-conservative proposals
:star: semi-conservative replication would produce 2 copies that each contained one of the original strands and one new strand
conservative replication would leave the 2 og template DNA strands together in a double helix, with the new DNA composed entirely of 2 new strands
dispersive replication would produce 2 copies of the DNA, both containing a mixture of old and new material
Meselson-Stahl Experiment
1958 Meselson and Franklin Stahl provide evidence that hypothesis that DNA replcation was semiservative
saw that nitrogen was a major constituent of DNA and 2 forms of DNA are available: ^14 N and heavier isotope of ^ 15 N
DNA grown in 15N medium have high density than cell grown in 14N medium
Experiment done by growing E. coli in 15N and tuened into N14
Helicase and Polymerase
DNA polymerase
: build the complementary DNA strand
Leading strand / lagging strand
: allow 2 new strands of DNA to be build in opposite directions
DNA replication begins as
DNA helicase
(type of enzyme) breaks the hydrogen bonds holding the 2 strands together and form a replication fork= 2 branching strands of DNA backbone with exposed bases(allow DNA to be read by DNA polymerase)
leading strand is the DNA strand that DNA polymerase construct in the 5'>3' direction
5' > 3'
lagging strand is the DNA strand at the opposite side of the replication fork from leading strand, going 3' > 5', and po;ymerse cannot be built
lagging strand is synthesized in short segments=
Okazaki Fragments
lagging strand= primase (enzyme) builds a short RNA primer and DNA polymerase is able to use 3'-OH group on the RNA primer to make DNA in the 5' > 3' direction, allowing RNA fragments to be degraded and new DNA nucleotide are added to fill gaps where RNA was present then DNA ligase is
able to attach (ligate)
the DNA nucleotide together= completion of the synthesis of lagging strand
Replication Forks:
develop along a chromosome
during mitosis or I of meiosis= molecules of DNA condense into a chromosome made of 2 identical "sister" chromatides (process ensures that cells that result from cell division have identical set of genetic material and DNA is exact copy)
RNA
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Ribonucleic acid is other nucleic acid with specific function during protein synthesis (allows to be involved is ability to fold into three-dimensional structures)
Transcription:
information in a gene is being transcribed into an RNA molecule
Gene
: segment of DNA that contains information to encode an RNA molecule or a protein
Gene Expression:
occurs only when gene product required by cell (cells are not so similar)
genes are embedded within DNA in the nucleus
RNA are small so they are able to carry information out of the nucleus(process occurs when gene product is needed by the cell )
Ribosome:
side of protein synthesis
information in DNA is transferred into RNA and RNA information is used to make protein
Three Types:
rRNA, mRNA, tRNA
mRNA copies the genetic instructions from DNA in the nucleus and carries them to the cytoplasm
protein syntheses occurs through transcription of DNA and translation of mRNA