dna & rna
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DNA & RNA. Transcription , & Translation. Biology 1. DNA!. By Mr. Ghormley. The History. Griffith developed the idea of DNA as the genetic material of organisms One strain of bacteria can be changed by another strep. pneumonia experiment. S + Mouse = Death R + Mouse = Mouse Lives - PowerPoint PPT PresentationTRANSCRIPT
By Mr. Ghormley
DNA!
Biology 1
The History
• Griffith developed the idea of DNA as the genetic material of organisms– One strain of bacteria can be changed by another– strep. pneumonia experiment
• S + Mouse = Death• R + Mouse = Mouse Lives• S + Heat = SH (aka Mouse Lives)
• SH + R + Mouse = Death– found that a normally non-pneumonia causing
Rough bacteria transformed R into live S cells
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Avery
• Avery continued Griffith’s work– Concluding that DNA was released from killed S
cells.– The R cells incorporated these DNA parts into their
genetic makeup, making them into S cells
Dead S + Live R = Live S because of DNA
Hershey & Chase• Proved DNA is the transforming factor by
using radioactive isotopes 32P and 35S to mark either Proteins or DNA in a virus that was bacteriophagic.– Traced lineage of the radioactive isotopes down
the generational line of bacteria to determine if DNA or proteins are passed to following generations
• Phosphorous used to bind to DNA• Sulfur used to bind to proteins
Watson and Crick
• James Watson (American) & Francis Crick (Brit) came up with the shape of the DNA molecule in 1953—double helix (spiral ladder)
DNA is a double stranded spiralor a twisted ladder, called a Double Helix.
DNA stores information,
It carries the information that the cell needs to function, grow and divide
DNA• Nucleic Acid molecule
that contains hereditary material—tells cell its function and structure
• Made of a 5 C sugar (deoxyribose) attached to a phosphate grp (PO4) and a N base—3 grps bond to form a nucleotide
• Sugar & PO4 always same, form the backbone or sides of the ladder
Nitrogen Bases• Purine:
– Adenine– Guanine
• Pyrimidine:– Thymine– Cytosine
• One Purine always bonds with one Pyrimidine.• Nitrogen bases held together by H bond to form
the “rung” of the ladder• Adenine(A) ALWAYS bonds to Thymine(T)
Guanine(G) ALWAYS bonds to Cytosine(C)
Will these superheroes’ powers ever wear off? Why or why not?
DNA Replication• When the cell is preparing to
divide, DNA must make copies of itself to go into the new cell
• Many enzymes are required to unwind the double helix and make a new strand
• Topoisomerase unwinds the supercoil
• Helicase unwinds original double strand
• DNA polymerase attaches new nucleotides to both strands
• Takes place during “S” phase of Interphase—more on that later
1. DNA opens (unzips), separating into 2 strands.
2. Free Nucleotides (A, T,G,& C) match up and join the open DNA strands.
3. Two identical DNA molecules are
formed.
DNA Replication
It translates the code of DNA and carries it to the ribosomes —where the amino acids are brought together to form protein.
Messenger
(m)RNA
Transfe
r
(t) RNA
Ribosomal (r)RNA
RNA• Same primary structure of
DNA; sugar-phosphate backbone attached to a 5 C sugar
• Sugar is ribose, instead of deoxyribose
• RNA is a single strand, not a double helix, due to an extra hydroxyl grp (OH) on its sugar
• Uses uracil, instead of the N base thymine
• 3 types: mRNA—messenger RNA is the copy of the gene
• tRNA—transfer RNA carries the amino acids to the ribosomes from the cytoplasm
• rRNA—ribosomal RNA helps mRNA bind to the ribosome
1. Only one half of the DNA strand is transcribed;Both DNA strands are replicated.
2. Transcription produces only a single strand of RNA.
3. Uracil replaces thymine in transcription.
4. In replication, the DNA strand completely unzips, however; in transcription the DNA molecule only partly unzips.
1. The DNA molecules opens along a gene.
3. Nucleotides of RNA match up to the open DNA strand.
4. The completed strand of RNA (messenger) moves from the nucleus to the cytoplasm. The DNA “zips” back up.
2. A segment of the DNA in the nucleus is “copied” into a molecule of RNA called mRNA or messenger RNA
Transcription
A
G
C
T A
G
C
T
Transcription
• One strand acts as a template, free nucleotides form the other half
• RNA polymerase forms sugar-phosphate bonds between nucleotides
A
G
C
TA
G
C
U
A
G
C
T
Transcription
• The mRNA detaches from the DNA strand• The two DNA strands join together by complementary
base pairing• The DNA molecules winds back up into a helix
A
G
C
TA
G
C
U
A
G
C
T
Transcription• The sequences of 3 bases on the
mRNA coding for amino acids are called CODONS.
• Not all the bases in the DNA code for amino acids so the mRNA just transcribed contains non-coding regions known as INTRONS
Ribosomes must translate the language of nucleotides into the language of amino acids.
Is the assembly of amino acids in proper sequence to create proteins.
Takes place in the cytoplasm.Ribosomes “read” the info encoded on mRNA and use it for protein synthesis.
This keeps DNA pristine and protected, away from caustic chemistry of cytoplasm
3. The ribosome attaches one amino acid to another as it moves along the mRNA.
4. The tRNA molecules are released after the amino acids they carry are attached to the growing chain of amino acids.5. The ribosome completes the translation when it reaches the end of the mRNA strand. The newly made protein molecule, in the form of a chain of amino acids, is released.
1. Translation begins when a ribosome attaches to the beginning end of an mRNA molecule.
2. A tRNA molecule carrying an amino acid matches up to a complementary triplet on a mRNA on the ribosome.
Translation
Genetic Code• Each amino acid is specified by
a particular combination of 3 nucleotides, called codons
• Different species can use one codon over another for the same amino acid—giraffe use CGC for arginine over CGA
• Precise arrangement of these pairings of nucleotides form genes –each DNA molecule has 1000’s of genes, which are lined up like cars on a long train
Chromosomes• Prior to mitosis, DNA coils up
into chromosomes that look like a fuzzy X
• Chromatids are half of a replictated chromosome
• Centromere ( protein disk) holds the 2 chromatids together
• Located in different location on each chromosome
• Each chromosome has its own size
• Humans have 23 pairs of different chromosomes
Mutations
• A permanent change in a cell’s DNA• Types of mutations
– Missense (Substitution)– Nonsense (Substitution– Deletion (Frameshift)– Insertion (Frameshift)– Duplication (Duplicates a codon)– Expanding Mutation (repeats a codon)
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