BIOL10005 Lecture Notes - Lecture 1: Dna Ligase, Okazaki Fragments, Structural Stability
Monday, 24 July 2017
Genetics
What is genetics?
• Study of variation between and among living things, and how this variation is
inherited
•Genotype- genetic constitution
•Phenotype- morphological, biochemical and behavioural properties of an organism
resulting from a specific genotype and its interaction with the environment
• Genome- Total amount of genetic material in a chromosomes (sequence- bases)
(nuclear or mitochondrial)
Variation
Environmental factors e.g. Fetal Alcohol Syndrome (FAS) but Alcohol Metabolism
(alcohol dehydrogenase)?
Genetic factors e.g. huntington disease
A combination of genetic and environmental factors (coat/flour colour)
Epigenetics
Epigenetic change is a change in gene expression without changing the DNA code
Human Polymorphism
-Variations with no differences to viability
-Variations with differences to health
Genes/DNA
Gene: The fundamental physical and functional unit of heredity, which carries
information from one generation to the next
DNA- polynucleotide, hydrogen bonds weaker and easily broken, backbone much
stronger
Purines (Adenine and Guanine) and pyrimidines (Cytosine and Thymine)
Purine pairs with pyrimidine (double carbon ring with a single ring)
!1
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Monday, 24 July 2017
C-G - 3 hydrogen bonds
A-T - 2 hydrogen bonds
Genes are located in mitochondria, chloroplast and plasmids
Position of gene is called a locus
DNA + Protein = Chromatin
Chromosomes when DNA condense
Nucleosome - DNA with special histones (wrapped twice around 8 proteins, H1
clamps)
Chromosomes may consist of one or two molecules of DNA (sister chromatids joined
at centromere)
DNA replication occurs during the S (synthesis) stage of the cell cycle, has specificc
checkpoints
DNA replication
Semi-conservative
Prokaryote-
One origin of replication
Synthesis occurs in both directions
Eukaryote-
Multiple origins of replication
Both directions
Same time
Very quick
Enzymes involved-
Helicase separates strands
Single stranded binding proteins keeps strands apart
DNA Topoisomerase (gyrase) relieves tension of closed DNA
RNA primase adds single stranded RNA (primer) to signal beginning 5’ to 3’
DNA polymerase III (replication for DNA in E.coli)
!2
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Monday, 24 July 2017
Leading strand is continuous replication
Lagging strand goes away from replication fork, discontinuous process because have
to go from 5’ to 3’ , forms Okazaki fragments , DNA polymerase 1 removes primers,
then joined by DNA ligase
Beta clamp joins DNA polymerase to strand
Prokaryote v Eukaryotic replication:
Okazaki fragments:
P: 1000 bases
E: 100-200 bases
Speed:
P: 30 000 bases/min
E: 3000 bases/min
Enzymes:
P: DNA polymerase 3
E: Several DNA polymerases
Errors in DNA- how they are repaired
1. Errors during replication can be replaces on the spot DNA goes back and cuts out
mistake
2. Adds bases forwards, removes them backwards
Chromosomes
Require 3 elements to function
Telomeres: Structural stability
Centromere: Essential for segregation at cell division
Origins of replication: Start point
Telomere s
-Repeated sequences at telomere
!3
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
A combination of genetic and environmental factors (coat/ our colour) Epigenetic change is a change in gene expression without changing the dna code. Gene: the fundamental physical and functional unit of heredity, which carries information from one generation to the next. Dna- polynucleotide, hydrogen bonds weaker and easily broken, backbone much stronger. Purines (adenine and guanine) and pyrimidines (cytosine and thymine) Purine pairs with pyrimidine (double carbon ring with a single ring) Genes are located in mitochondria, chloroplast and plasmids. Nucleosome - dna with special histones (wrapped twice around 8 proteins, h1 clamps) Chromosomes may consist of one or two molecules of dna (sister chromatids joined at centromere) Dna replication occurs during the s (synthesis) stage of the cell cycle, has speci cc checkpoints. Dna topoisomerase (gyrase) relieves tension of closed dna. Rna primase adds single stranded rna (primer) to signal beginning 5" to 3". Dna polymerase iii (replication for dna in e. coli)
