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inherited DNA leads to specific traits by dictating the synthesis of proteins
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Gene expression
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process by which DNA directs protein synthesis (2 stages)
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Transcription
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the synthesis of RNA using a DNA template
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Translation
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the synthesis of a polypeptide using the genetic information encoded in mRNA. (nucleotides to amino acids)
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inborn errors of metabolism
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inherited diseases when a person can't make a specific enzyme (no gene for enzyme bc of mutation)
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ex.
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alkaptonura
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pee is black because no enzyme exists to break down alkapton
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one gene-one polypeptide hypothesis
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gene dictates the specific production of an enzyme
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(gene codes for a polypeptide aka protein aka enzyme)
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DNA
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RNA
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strands
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double and anti-parallel
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single
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3 part of nucleotides: 5-C sugar:
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deoxyribose
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ribose
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phosphate group:
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present
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present
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nitrogenous base
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C, G, A, T
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C, G, A, U
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mRNA
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synthesized using DNA template, attaches to ribosome in cytoplasm and specifies the primary structure of protein
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rRNA
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molecules...and proteins make up the ribosomes
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tRNA
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translates between nucleic acid (DNA) and protein lang. by carrying specific amino acids to ribosome, where they recognize the appropriate codons in the mRNA
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eukaryotes
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nucleus (where DNA is)
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prokaryotes
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cytoplasm
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RNA polymerase II
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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
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promoter
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DNA sequence where RNA polymerase II starts transcribing
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terminator
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DNA sequence where RNA polymerase II stops transcribing
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transcription unit
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the entire stretch of DNA transcribed in mRNA
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initiation
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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
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Elongation
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RNA polymerase moves downstream, unwinding and elongating
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Termination
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polymerase transcribes a sequence in DNA signaling end, RNA transcript is released, polymerase detaches from DNA
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ends of pre-mRNA molecule are modified before leaving the nucleus
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GTP cap
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5' end receives guanine triphosphate cap
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poly-A tail
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3' end gets adenine nucleotides
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RNA is made of :
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exons (expresses code) and introns from DNA
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INTRONS are cut out, while EXONS are spliced together by RNA splicing
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RNA splicing signals are at both ends of an INTRON
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protein spliceosome snips out intron from transcript
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enzyme of protein = ribozymes
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DNA and RNA
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polymers of nucleotides
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nucleotides differ in bases
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A,T,C,G vs. A,U,C,G
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Genetic code
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'language' of mRNA instructions
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codon
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mRNA, 3-letter word
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3 nucleotide that code for an amino acid
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UCG =
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amino acid methionine
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proteins
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amino acids join in polypeptide
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ALL proteins have a start (AUG) and terminator codon
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prokaryotes & eukaryotes
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cytoplasm on the ribosome
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mRNA
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left nucleus, now in cytoplasm, binds to ribosome
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rRNA
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ribosome composed of rRNA and protein; adds amino acids to polypeptide chain
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- 3 binding sites:
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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
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tRNA
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transfers amino acids to ribosome
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other end of tRNA has anti-codon
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polyribosomes
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mRNA can be translated simultaneously by several ribosomes
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alteration in the genetic information of a cell
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point mutation - affects one nucleotide pair
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nucleotide-pair substitution - replacement of one nucleotide and it's complementary base pair in DNA
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1. silent mutations do not change amino acid translation
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2. missense mutation substitution when a codon still codes for an amino acid
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3. nonsense mutations - substitutions when a regular amino acid codon is changed into a stop codon, ending translation
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insertion and deletion - addition / loss of nucleotide pairs, can cause frameshift, mRNA read wrong
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mutagens - forces that interact with DNA in ways that cause mutation
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ex. x-rays
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
