Gene to Proteininherited 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 Garrodinborn errors of metabolism | inherited diseases when a person can't make a specific enzyme (no gene for enzyme bc of mutation) | ex. | alkaptonura | | | pee is black because no enzyme exists to break down alkapton |
Beadle and Tatumone gene-one polypeptide hypothesis | gene dictates the specific production of an enzyme | | | (gene codes for a polypeptide aka protein aka enzyme) |
DNA vs. RNA| | 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 RNAmRNA | 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 | | TRANSCRIPTION is DNA-directed synthesis of RNAeukaryotes | nucleus (where DNA is) | prokaryotes | cytoplasm | RNA polymerase II | binds to DNA and separates DNA strands | | | pastes complimentary RNA nucleotides to one side of DNA strand | | | = 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 | | | prokaryotes do this themselves | | | eukaryotes use proteins called transcription factors to assist bind of RNA polymerase to strand | | | 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 Transcriptionends 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 | | | 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 | | | enzyme of protein = ribozymes |
| | Genetic CodeDNA 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 | | | 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 |
Translationprokaryotes & 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 | | | P site: holds the tRNA that carries the growing polypeptide chain | | | E site: exit site for tRNA | tRNA | transfers amino acids to ribosome | | | 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 Mutationsalteration 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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