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Neurospora crassa is?
- a common bread mold/fungus
- haploid alleles
- minimal nutrients needed
- used for mutation expirement
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Mutagen
something taht causes mutations
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Mutation
inherited genotypic changes
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One-gene, One-enzyme hypothesis
genes are related directly with enzymes
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one-gene, one-polypeptide relationship
a gene and a polypeptide are closely related
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Steps for going from DNA to protein (the central dogma of molecular biology)
- transcription - info in DNA is copied onto a complimentary RNA sequence
- Translation - the RNA sequence is used to create that amino acid sequence of a polypeptide
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RNA's differences to DNA
- RNA usually only has one polynucleotide strand
- sugar molecule in RNA is ribose
- Has uracil (U) instead of Thymine (T)
- -so A=U as C=G
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3 Types of RNA and Functions of each
- Messenger RNA (mRNA) - carries a copy of a gene sequence in DNA to a ribosome
- Transfer RNA (tRNA) - carries amino acids to the ribosome for assembly into polypeptides
- Ribosomal RNA (rRNA) - catalyzes peptide bond formation and provides frame work for ribosome
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Codons
- 3 consecutive nucleotides
- informational sequence
- different codons encode different amino acids
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transcript
the mRNA copy of a gene
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reverse transcription
synthesis of DNA from RNA
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Componants of transforming RNA to DNA
- DNA template for base pairing
- the appropriate substrates
- an RNA polymerase enzyme
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RNA polylerase
catalyze the synthesis of RNA from the DNA template
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Transcription steps
- Initiation - promoter a sequence of DNA (AUG) that binds with RNA polymerase
- Elongation - RNA polymerase unwinds the DNA about 10 base pairs at a time and reads it 3' to 5'
- Termination - ends process
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genetic code
specifies whis amino acids will be used to build a protein
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Start codons
AUG - initiates the signal for translation
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stop codons
UAG/UAA/UGA - terminate signals for translation
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terminator
signals the end of transcription
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introns
INtervening RegiONS - noncoding base sequences
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Exons
EXpressed regiONS - coding sequences
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Both introns and exons make
primary mRNA transcript (Pre-mRNA)
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Nucleic acid hybridization
- method for locating introns
- 1- target DNA is denatured
- 2- probe incubated with denatured DNA
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Probe
a single-stranded nucleic acid from another source
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domains
different functional regions of a protein
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G cap
- added to 5' end of Pre-mRNA as transcribed
- molecule of GTP
- helps bind mRNA to ribosomes for translation
- protects mRNA from being digested by ribonucleases
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Poly A tail
- added at 3' end of pre-mRNA at the end of transcrition
- acts as a signal for an enzyme to cut the pre-mRNA
- assists in export of mRNA from nucleus
- helps with mRNA stability
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RNA Splicing
process that removes introns and splices the exons together
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small nuclear ribonucleoprotein particals
binds the the ends of exons near the splice sites
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spliceosome
- RNA protein complex formed by protiens added using ATP
- cuts pre-mRNA, releases the introns, and rejoinds at exons to produce mature mRNA
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tRNA functions
- bind to a praticular amino acid (charged)
- associates with mRNA
- interacts with ribosomes
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ribosome
- "work bench" of translation
- holds mRNA and tRNA in position for polypeptide assembly
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ribosome's 2 subunits
- Large - contains A (amino acid) site, P (polypeptide) site, and E (exit) site
- small - binds to sequence on mRNA
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polyribosomes/polysomes
combination of mRNA strand, ribosomes, and polypeptides
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signal sequence
indicates where in the cell the polypeptides belong
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docking protein
- a specific receptor protein that a signal sequence binds to
- on the outer membrane of an organelle (nucleus/mitochondrion/chloroplast)
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signal recognition particle
- a particle composed of protein and RNA that the signal sequence binds to
- in ER
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modifications after translation
- proteolysis
- glycosylation
- phosphorylation
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proteolysis
cutting of the peptide chain to allow fragments to fold into different shapes
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glycosylation
adding sugars to improve targeting and recognition
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phosphorylation
add phosphate groups to alter the shape of the protein
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