DNA And How Genes Work Flashcards
Which direction to strands of the DNA helix run in?
Anti parallel
What makes up a nucleoside?
Sugar and base
What makes up a nucleotide?
Sugar, base and phosphate
Which direction are sequences written in?
5’ - 3’
How is DNA packaged?
Packaged as chromatin, which is wrapped around histones
How is DNA replicated?
Hydrogen bonds of DNA are broken as the helix unwinds.
Complementary strand of DNA is built in the 5’-3’ direction. Each new base is linked via a phosphate group to the 3’ OH of the growing strand. Pyrophosphate released as each base is added.
Ozaki fragments of lagging strand are joined together by DNA polymerase in a process called backstitching.
How can DNA polymerase correct its own mistakes?
DNA polymerase checks the previous base is correct before adding a new one (proof reads) and fixes the mistake if not (mismatch repair)
What is transcription?
Copying of DNA into mRNA, using rna polymerase
What is the difference between RNA and DNA?
RNA is single stranded, uses ribose sugar, has uracil.
DNA is double stranded, uses deoxyribose sugar, has thymine.
What are the key elements for transcription that a gene has?
Transcription start site - copying of DNA strand into RNA begins.
TATA box - signal for start of transcription.
Promoter - where transcription factors bind.
Terminator sequence - signal for RNA polymerase to stop copying the DNA template into RNA.
How is mRNA processed?
It’s spliced to remove introns, a polyA tail and 5’ cap is added to support export from the nucleus.
What is translation?
Formation of proteins from RNA, using codons to determine amino acid sequences.
What is the start codon?
Met (AUG)
What are the end codons?
UGA, UAA, UAG
What are transfer RNAs?
Bring each of the 20 amino acids to the growing protein, contain an anti colon region so the codon for each amino acid can be recognised.
