the expression of genes Flashcards
what is rRNA
ribosomal RNA, makes ribosomes, it is the last set of genes to be turned off before cell division
What is tRNA
transfer RNA, carries amino acids to ribosome during protein synthesis
- they have an anticodon on one and carry the amino acid on the other. the anticodon will connect to the codon on the mRNA
- it is RNA that is all folded up
mRNA
messenger RNA, a copy of DNA that contains the information for protein synthesis.
How does transcription work
DNA is used to make mRNA,
- only genes are transcribed not all DNA; in front, there is a promoter sequence and a terminator sequence at the end (prokaryotes)
- RNA sequence is complementary to DNA
- new nucleotides are added on the 3’ end of the RNA and the synthesis in antiparallel
what is complementary to what (nitrogenous bases)
A - T (U in RNA)
G - C
what do polymerase do
unwind and separate double-stranded DNA, read DNA template, adds RNA nucleotides, and reorganized promoters and terminators.
rules for eukaryotes
- 5’ cap is added at the for it to last longer and help transport; a modified guanine
- introns are removed by spliceosomes, exons are kept (pre-mRNA to mRNA)
- poly-A-tail at 3’ end to help transport mRNA (it is in back, it is the motor, propulsion); multiple adenine (poly-A)
- caps are put because they need to get out of the nucleus therefore last longer.
what is translation
assembly of amino acids into polypeptides
how are amino acids polymerized
they have an N-terminal and a C-terminal (nitrogen on one end and carbon of the order) and they are arranged so the N-terminal is in front.
what direction is mRNA read
5’ to 3’, 5’cap to poly A tail (tail is at the end)
where are amino acids taken
in enzymes, tRNA goes and gets the amino acid
what is a stop codon
codons that cannot be recognized by a tRNA, UAG, UAA, UGA are stop codons. when they have seen the ribosome breaks into subunits
What is a start codon
AUG (also an amino acid)
how are tRNA molecule produced
They are synthesized by RNA polymerase III (does like a ribosome but for RNA), (reads DNA and makes an RNA copy)
What are genes
section of DNA, from promoter to terminator. Read from 3’ to 5’ because you add basses on the 3’ end of RNA (so 5’ end of RNA is in front and they are antiparallel)
Types of mutation
Somatic mutation; mitosis in daughter cells
Germline mutation; before meiosis and end up in gametes
base substitutions
Silent mutation: base mutation but codon still codes for the same protein so phenotype stays the same
missense mutation: new codon; so new protein, may change phenotype
non-sense mutation: creates a stop codon, protein is shortened
frameshift mutations
deletion: a base pair is deleted; will shift the next amino acid creating new codons (changes all aa in exon after frameshift)
insertion; same but add one
Triplet deletion: lost one entire codon
triplet duplication or insertion
what is an inducible system?
a repressor is attached to the operator, this DNA is called an operon (genes). when an inducer attaches to the repressor it falls of allowing RNA polymerase to start transcription. This mRNA will be translated by ribosome creating the proteins needed.
If glucose is present no lac operon is needed
lactose is sugar so if there is already glucose no need for more
lacZ
a first structural gene on the operon; codes for enzyme B. galactosidase; breaks down lactose into glucose and galactose (lacZ, lacY, lacA) antialphabetical
what is the lac operon
an inducible system that only exists in E. Coli; genes in this operon are normally turned off, they turn on in the presence of lactose (procaryote regulation)
lacY
second structural gene on the operon; enzyme opens up the cell to let lactose enter (protein channel)
lacA
last structural gene in the operon; codes for enzyme transacetylase
