Chapter 13: Gene Structure and Expression Flashcards
Transcription of a gene occurs in what three steps?
- initiation
- elongation
- termination
guanine cap
added to 5` end of the pre-mRNA by a capping enzyme during transcription
-protects mRNA from degradation and where the ribosomes attach during translation
direction of transcription
downstream
transcription initiation complex
transcription factors and RNA polymerase
In eukaryotes, added to the 3` end during replication is….
polyadenylation signal (poly A polymerase adds a chain of 50 to 250 adenine nucleotides)
mRNA
messenger RNA; possesses the code for a particular polypeptide chain on it
codon
3 nucleotide bases that code for a particular amino acid
How many codons are there?
64 (60 without the start codon and stop codons)
AUG
start codon (starts translation)
Bacterial mRNAs can usually be __________.
immediately translated
Prokaryotic mRNAs are translated by ribosomes ______________.
while they are still being transcribed by RNA polymerases
pre-mRNA
precursor mRNA (initial mRNA transcribed)
After processing the RNAs are called….
mature mRNAs
Eukaryote mRNAs must undergo ___________ before they are ready to leave the nucleus.
processing in the nucleus
poly (A) tail
protects the RNA from attack by RNA digesting enzymes in the cytosol
introns
sections not included in the mature mRNAs
exons
sections that are included in the mature mRNA and translated
RNA splicing
removes introns
ribosomes are….
ribonucleoprotein particles (ribosomal RNA and proteins)
initiator tRNA
anticodon UAC
stop codons
UAG, UAA, UGA (they have no complementary anticodon)
release factor protein
binds to stop codons
polysome/polyribosome
an mRNA and associated ribosomes (speeds up the synthesis of the required polypeptide)
after proteins leave the ribosome, most are folded or modified in what is called….
post translational modification
In many animals mutations have to affect cells in the _____________ in order to be passed on to subsequent generations.
germ line
somatic mutations do not have evolutionary significance in animals unless it’s an animal capable of reproducing by…
cloning
base substitution mutations
-incorrect base is substituted, resulting in a change in base sequence on both strands (change in a codon)
silent mutation
if the amino acid coded for is exactly the same the one one coded for by the original codon
missense mutation
cause a change in a single amino acid in the encoded polypeptide
nonsense mutations
converts a normal codon to a stop codon causing the translation to stop
frameshift mutation
addition or deletion of a nucleotide
