Lecture 3 Flashcards
What does DNA consist of?
DNA consists of two antiparallel strands of complementary bases?
What way are bases added onto DNA
Added from 5’ to 3’ (5 prime to 3 prime)
What is a nucleoside?
Sugar and a base
What are the differences in DNA and RNA
DNA - ATGC
RNA - AUGC
Which are the Purines?
Adenine and Guanine (2 rings)
Which are the Pyrimidines
Cytosine, Thymine, Uracil (1 ring)
What is the sense and antisense strands
Sense strand (coding strand) 5' to 3' Antisense strand (non- coding) 3' to 5'
How many chromosomes do we have?
46 chromosomes - 22 pairs and the XX (females) and XY (males)
What are the stages of DNA replication
Semi-conservative replication
Unwinding at the replication origin
Building complementary strand in 5’ to 3’ direction (DNA synthesis begins at replication forks)
Join fragments together
How are new bases added to the template strand?
Each new base is linked via a phosphate group to the 3’ OH of the growing strand
What is released when each base is added?
Pyrophosphate
How is DNA replication catalysed?
Catalysed by DNA polymerase - it stays attached and attaches new bases
What are Okazaki fragments?
Short strands made in the 5’ to 3’ direction, they are made in small pieces discontinuously, then DNA ligase joins the short strands together via back stitching
Where can mutations occur ?
Any region of the gene:
- exon
- intron
- promoter
- enhancer
What is a gene
The functional unit of the genome
Draw a gene in more detail
in notes
Whats the purpose of m7G
Increases stability
What is transcription?
DNA to mRNA, RNA polymerase is the main enzyme involved
What are the four key elements for transcription?
- TSS - Transcription Start Site
- TATA Box - signal for start of transcription
- Promoter - Where transciption factors bind to regulate transcription
- Stop Site - Signal for RNA to stop copying DNA template into RNA
Describe processing of mRNA
The introns are removed, coding regions are joined to produce mRNA and the poly A tail and 5’ cap are added for stability and export from the nucleus
What is a codon
Base triplet of amino acids
What do proteins start with
Met (AUG)
What do proteins always end with?
A stop codon (UGA, UAA or UAG)
What can a deletion of a base cause
A frameshift mutation
What is the role of transfer RNAs
Contain an anticodon that recognise the codon for each amino acid
What are the different sites and in what order
E site –> P site –> A site
What happens after translation?
Proteins are transferred to the Golgi apparatus for polishing
