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Chapter 11 : DNA & it's role in heredity - Coggle Diagram
Chapter 11 : DNA & it's role in heredity
Key features of DNA : double stranded helix and uniform diameter/ uniparallel / right handed/
• Outer edges of nitrogenous bases are
exposed in the major and minor grooves
DNA base pairing : Adinine-Thymine (2hydrogen bonds) // Guanine- Cytosine(3 hydrogen bonds). All base pairs consists of
1 purine & 1 pyrimidine
things i dont really understand: antiparallel strands
The placement of the phosphate group is what determines the direction of the strands, where this the sugar- phosphate molecule is 5' ending and where there is the the hydroyl group (-OH) it's a 3' ending
&
Functions of DNA: It stores gentic material; it contains millions of nucleotides and
the base sequence
stores and
encodes
multiple information & can undergo mutation and hence result in change of information
Genetic material is replicated during cell divison by complementary base pairing & it is expresses as the phenotype, the nucleotide sequence is what determines the amino acid sequence in proteins
3 types of DNA replication pattern: 1.Semiconservative: The new DNA are made of one parental strand and one newly replicated strand
2.Conservative : After replication the DNa are either entirely made up of parental strands or newly replicated strands
3.Dispersive: The DNA molecules are a mixture or hybrids of the parental and the daughter DNA.
N.B: Meselson and Stahl concluded that the semicoservative replication is the correct one
Replication of DNA,2 steps: 1.The double helix strand is unwided to form two template strands
2.To the 3' ending nucleotides are added linked by phospphodiester bonds; the sequence is detrmined by the complemantary base pairs
Helicase unwinds the double strands; it's uses energy from the hydrolysis of ATP
Topoisomerase(DNA gyrase) is added to prevent supercoiling
Single strand biding proteins are added onto the strands to prevent them from snapping back together
Primers made by primerase are added to the strands, this enables the replication to begin
DNA Polymerase III starts adding complementary nucleotides in the 5' to 3' direction creating the leading strand
Since replication is semi-discontinous Okazaki fragments are formed on the lagging strand because this where replication is discountinous
DNA polymerase I replaces the primers with DNA then DNA ligase seals the ninx.
DNA polymerase I & III have 3' to 5' exonuclease activity meant to proofread while DNA polymerase I also has 5' to 3' exonuclease activity for DNA repair
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