DNA transcription Flashcards
What are the 4 chemical bases of DNA?
A - adenine
G - guanine
C - cytosine
T - Thymine
What are bases attached to?
A sugar molecule and a phosphate molecule (makes up the sugar-phosphate backbone)
What 3 parts comprise a nucleotide?
Base
Sugar
Phosphate
What are chromosomes made of?
Tightly coiled DNA
What is DNA coiled around to form the chromosome?
proteins called histones
What is the centromere?
the constriction point of the chromosome (the centre of the X shape)
Which arm of the chromosome is the p arm and which is the q arm?
p arm = the short arm
q arm = longer arm
Define transcription
The process whereby a genetic template for a protein is copied and carried out to the cytoplasm
Which enzyme catalyses transcription?
RNA polymerase
What are the 3 main steps of transcription?
Initiation
Elongation
Termination
What happens in the initiation phase of transcription?
RNA polymerase attaches to the DNA strand
Binds to promotor sequence of DNA
Enzyme unwinds a portion of the DNA, exposing bases
Describe the structure of DNA
Two long strands of nucleotides spiralling into a double helix, where bases are paired and connected to a sugar-phosphate backbone
Describe the structure of a chromosome
a chromosome is tightly packed DNA, coiled in a thread-like structure around histones (proteins)
What is a chromatid?
One side of the chromosome
How many chromatids make a chromosome?
2
What shape are phosphate molecules?
pentagon
What does the promotor sequence do in the initiation phase of transcription?
It informs the RNA polymerase enzyme where to begin transcription
What happens in the elongation phase of transcription?
The template strand is read in a 3’ to 5’ direction
RNA polymerase uses ribonucleotides to form the mRNA strand (template) using complementary base pairing
What happens in the termination phase of transcription?
When RNA polymerase encounters a stop sequence, elongation stops
RNA polymerase detaches from the gene
it releases the mRNA into the cytoplasm to find a ribosome