Chapter 10.6 - 10.16 Flashcards
what are the two stages of protein synthesis
transcription and translation
transcription
transfer of genetic information from DNA to RNA; in the nucleus
translation
transfer of information in RNA into a protein; at ribosomes
what is a gene
Sequences coding for specific proteins
Genotype (DNA) -> phenotype (trait)
what is a codon
nitrogenous bases represent “letters” in an “alphabet” that can form “words”
codon is a three letter “word”
one codon codes for one amino acid
how many nucleotides make up a codon
three
what is the AUG triplet
methionine / START codon
what are the three STOP triplets
UAA, UAG, UGA
what information does the genetic code supply
correspondence between codons in mRNA and amino acids
initiation (transcription)
RNA polymerase attaches to promoter (specific binding site, humans TATA), RNA synthesis begins
elongation (transcription)
RNA synthesis continues, transcribed section releases, helix reforms
termination (transcription)
RNA polymerase reaches a terminator (specific sequence of bases) signaling the end of the gene and detaches
what is RNA polymerase
an enzyme that copies a DNA sequence into an RNA sequence during transcription
what is the purpose of mRNA
carries the information from DNA to make proteins
In RNA processing, what purpose does adding extra nucleotides to the ends of mRNA serve?
facilitate export of mRNA from nucleus, protect mRNA from cellular enzymes, help mRNA bind to ribosomes
introns
noncoding regions that are removed in RNA processing in eukaryotes
exons
expressed areas that are spliced by RNA
tRNA
transfers specific amino acids to ribosome
anticodon
end base pairs with mRNA codon
what role do ribosomes play in translation?
help build polypeptides
create peptide bonds between amino acids to create a polypeptide chain
what are ribosomes made up?
2 subunits made up of proteins and ribosomal RNA (rRNA)
initiation (translation)
Step 1: mRNA binds to a small ribosomal subunit, initiator tRNA carrying the amino acid Met binds to start codon
Step 2: large ribosomal subunit binds to the small unit, initiator tRNA fits into the P site, A site is vacant to receive tRNA
elongation (translation)
Codon recognition: anticodon pairs with codon
Peptide bond formation (covalent bonds between amino acids): amino acid separates from tRNA and forms a peptide bond with the next amino acid
Translocation: P site tRNA leaves and ribosome moves tRNA in A site to P site, repeat steps
termination (translation)
when a STOP codon reaches the A site polypeptide is released
what is a mutation?
any change in the nucleotide sequence of DNA
positive, negative, or neutral (silent mutation) effect
mutagens
physical or chemical agents causing mutations
types of genetic mutations
base substitutions (point) base insertions or deletions (frameshift)
base substitutions (point)
replace one base with another
base insertions or deletions (frameshift)
alter the reading frame
