483 Lecture Notes - Lecture 7: Endoplasmic Reticulum, Cytosol, Radiography
LECTURE 7 Gene expression
DNA replication
Complicated process • >12 enzymes and proteins involved
• 50 nucleotides per second! • Use existing strands (parental) as templates to synthesise new
strands.
DNA replication
•Starts at several specific points ‐ origins of replication
• Replication bubbles
• Eventually, join to make new strands
Several enzymes involved, including:
–DNA gyrase: unwinds old DNA strands
–Helicase = separate the DNA strands
–DNA polymerase = links new nucleotides together
– DNA ligase = repairs break in DNA backbone
Leading strand ‐ replication can take place in one continuous line from 5’ ‐ 3’.
Lagging strand ‐ replication occurs in pieces generating fragments called Okazaki fragments.
From DNA to protein
•Biological information is encoded in DNA
•Biological function emerges from proteins
•DNA needs to be translated into proteins
Transcription and translation
A gene doesn’t build a protein directly…
1. DNA sequence of a
gene is transcribed into mRNA in the nucleus
2. mRNA is translated into a protein in
RNA
• Polymers of nucleotides (1 base, one phosphate
the group, and sugar ribose)
•A, C, G and uracil (A‐U and G‐C)
•Two types of RNA 1. messenger
RNA 2. transfer RNA
1. Transcription •From DNA to mRNA…
•Messenger RNA (mRNA) –Produced in the nucleus by transcription
–Carries genetic info from DNA to ribosomes (protein synthesis site)
–Codon = a three-base sequence in mRNA that corresponds to an individual amino acid
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Document Summary
Complicated process >12 enzymes and proteins involved: 50 nucleotides per second, use existing strands (parental) as templates to synthesise new strands. Dna replication: starts at several specific points origins of replication, replication bubbles, eventually, join to make new strands. Dna ligase = repairs break in dna backbone. Leading strand replication can take place in one continuous line from 5" 3". Lagging strand replication occurs in pieces generating fragments called okazaki fragments. From dna to protein: biological information is encoded in dna, biological function emerges from proteins, dna needs to be translated into proteins. A gene doesn"t build a protein directly : dna sequence of a gene is transcribed into mrna in the nucleus, mrna is translated into a protein in. Rna: polymers of nucleotides (1 base, one phosphate the group, and sugar ribose, a, c, g and uracil (a u and g c, two types of rna 1. messenger.