Gene to Protein
inherited DNA leads to specific traits by dictating the synthesis of proteins |
From Gene to Protein (cont.)
Gene expression |
process by which DNA directs protein synthesis (2 stages) |
Transcription |
the synthesis of RNA using a DNA template |
Translation |
the synthesis of a polypeptide using the genetic information encoded in mRNA. (nucleotides to amino acids) |
Achibald Garrod
inborn errors of metabolism |
inherited diseases when a person can't make a specific enzyme (no gene for enzyme bc of mutation) |
ex. |
alkaptonura |
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pee is black because no enzyme exists to break down alkapton |
Beadle and Tatum
one gene-one polypeptide hypothesis |
gene dictates the specific production of an enzyme |
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(gene codes for a polypeptide aka protein aka enzyme) |
DNA vs. RNA
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DNA |
RNA |
strands |
double and anti-parallel |
single |
3 part of nucleotides: 5-C sugar: |
deoxyribose |
ribose |
phosphate group: |
present |
present |
nitrogenous base |
C, G, A, T |
C, G, A, U |
3 Types of RNA
mRNA |
synthesized using DNA template, attaches to ribosome in cytoplasm and specifies the primary structure of protein |
rRNA |
molecules...and proteins make up the ribosomes |
tRNA |
translates between nucleic acid (DNA) and protein lang. by carrying specific amino acids to ribosome, where they recognize the appropriate codons in the mRNA |
PROTEINS ARE ASSEMBLED ON RIBOSOMES
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TRANSCRIPTION is DNA-directed synthesis of RNA
eukaryotes |
nucleus (where DNA is) |
prokaryotes |
cytoplasm |
RNA polymerase II |
binds to DNA and separates DNA strands |
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pastes complimentary RNA nucleotides to one side of DNA strand |
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= messenger RNA |
RNA polymerase DOES NOT need a primer
Transcription (cont.)
promoter |
DNA sequence where RNA polymerase II starts transcribing |
terminator |
DNA sequence where RNA polymerase II stops transcribing |
transcription unit |
the entire stretch of DNA transcribed in mRNA |
3 Stages of Transcription:
initiation |
after RNA polymerase binds to the promoter, the DNA unwinds and initiates RNA synthesis |
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prokaryotes do this themselves |
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eukaryotes use proteins called transcription factors to assist bind of RNA polymerase to strand |
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TATA box helps position mRNA polymerase |
Elongation |
RNA polymerase moves downstream, unwinding and elongating |
Termination |
polymerase transcribes a sequence in DNA signaling end, RNA transcript is released, polymerase detaches from DNA |
Modifying mRNA after Transcription
ends of pre-mRNA molecule are modified before leaving the nucleus |
GTP cap |
5' end receives guanine triphosphate cap |
poly-A tail |
3' end gets adenine nucleotides |
RNA is made of : |
exons (expresses code) and introns from DNA |
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INTRONS are cut out, while EXONS are spliced together by RNA splicing |
RNA splicing signals are at both ends of an INTRON |
protein spliceosome snips out intron from transcript |
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enzyme of protein = ribozymes |
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Genetic Code
DNA and RNA |
polymers of nucleotides |
nucleotides differ in bases |
A,T,C,G vs. A,U,C,G |
Genetic code |
'language' of mRNA instructions |
codon |
mRNA, 3-letter word |
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3 nucleotide that code for an amino acid |
UCG = |
amino acid methionine |
proteins |
amino acids join in polypeptide |
ALL proteins have a start (AUG) and terminator codon |
Translation
prokaryotes & eukaryotes |
cytoplasm on the ribosome |
mRNA |
left nucleus, now in cytoplasm, binds to ribosome |
rRNA |
ribosome composed of rRNA and protein; adds amino acids to polypeptide chain |
- 3 binding sites: |
A site: holds the tRNA that carries the next amino acid |
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P site: holds the tRNA that carries the growing polypeptide chain |
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E site: exit site for tRNA |
tRNA |
transfers amino acids to ribosome |
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other end of tRNA has anti-codon |
- reference drawing for explanation -
_
polyribosomes |
mRNA can be translated simultaneously by several ribosomes |
transcription / translation of BACTERIA cells occurs at same time because they're both in the CYTOPLASM
Mutations
alteration in the genetic information of a cell |
point mutation - affects one nucleotide pair |
nucleotide-pair substitution - replacement of one nucleotide and it's complementary base pair in DNA |
1. silent mutations do not change amino acid translation |
2. missense mutation substitution when a codon still codes for an amino acid |
3. nonsense mutations - substitutions when a regular amino acid codon is changed into a stop codon, ending translation |
Mutations (cont.)
insertion and deletion - addition / loss of nucleotide pairs, can cause frameshift, mRNA read wrong |
mutagens - forces that interact with DNA in ways that cause mutation |
ex. x-rays |
REMEMBER:
- most genes only contain instructions for assembling proteins
- many proteins = enzyme
- can control color of a flower
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This is what i need. I hope there is compilation of this
This is what i need. I hope there is compilation of this
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