Gene expression (Transcription/Translation) Flashcards
What is Chromatin?
DNA when the cell is not dividing – mass of fibres loosely wound around histone proteins and not visible with our microscopes
What are Chromosomes?
After DNA replicates, chromatin condenses into chromosomes.
What are Chromatids?
Each duplicated chromosome = 2 sister chromatids.
What are the 3 reasons DNA is activated?
1) To express your genes: make a protein & organelles
2) To make a whole new cell: Mitosis
3) Reproduction: Sexual cells / Meiosis
What is transcription?
The copying of a gene’s DNA sequence to make an RNA molecule - preformed by RNA polymerase
What is translation?
The process that takes the information passed from DNA as mRNA and turns it into a series of amino acids.
What are the 3 steps of transcription?
1) Initiation
2) Elongation
3) Termination
What is Initiation (Transcription)?
After the RNA polymerase binds to the promoter region, the DNA strand unwinds and polymerase initiates RNA synthesis.
What is elongation (Transcription)?
The polymerase moves downstream, unwinding the DNA & elongating the RNA transcription: the DNA rewinds its helix. (60 nucleotides/sec)
What is termination (transcription)?
Eventually, the RNA transcription is released and the polymerase detaches from the DNA and becomes mRNA.
What are the steps of translation?
1) mRNA binds w/small ribosomal subunit.
2) tRNA joins w/appropriate 3 bases – start code is always A-U-G.
3) The large ribosomal subunit joins:
a) codon recognition
b) Peptide bonds form between a.a.
c) tRNA moves to next codon down
4) Elongation: a.a. chain begins to elongate
5) Translation ends: when termination sequence (UAA, UAG, UGA)
What are the mistakes in the genetic code?
Alteration in gene (mutation), inherited (ie: sickle-cell anemia)
What is a point mutation?
Occurring in a genome, when a single base pair is added, deleted, or changed.
What are the types of point mutations?
Silent: No effect on the protein
Missence: Codes for a different amino acid than is supposed to be there.
Nonsense: Codon changed into a stop codon
Deletions: Removing one or more bases
Insertion: Inserting one or more bases
