1. Chapter 5. Replication & Recombination
Aala A. Abulfaraj

2. DNA Replication Is Semiconservative
Semiconservative replication:
DNA replication is done by separation of the strands of a parental duplex
Each strand then acting as a template for synthesis of a complementary strand.
The sequences of the daughter strands are determined by complementary base pairing with the separated parental strands.

3. Replication of The DNA
Replication of DNA is undertaken by a complex of enzymes that separate the parental strands and synthesize the daughter strands.
Denaturation – In DNA, this involves the separation of the two strands due to breaking of hydrogen bonds between bases.
Renaturation – The reassociation of denatured complementary single strands of a DNA double helix.
Polymerases Act on Separated DNA Strands at the Replication Fork

4. FIGURE: The replication fork
Replication of The DNA
The replication fork is the point at which the parental strands are separated.
The enzymes that synthesize DNA are called DNA polymerases.
Polymerases Act on Separated DNA Strands at the Replication Fork
FIGURE: The replication fork

5. Replication of The DNA
Nucleases are enzymes that degrade nucleic acids; they include DNases and RNases and can be categorized as endonucleases or exonucleases.
FIGURE : An endonuclease cleaves a bond within a nucleic acid
FIGURE : An exonuclease removes bases one at a time

6. DNA Recombination
Genetic recombination: A process by which separate DNA molecules are joined into a single molecule, due to crossing-over event
This cross -over produces a new combination of alleles
Recombination Occurs by Physical Exchange of DNA resulting in the exchange of genes between the two homologous chromosomes

7. DNA Recombination Recombination occurs by a breakage and reunion
The frequency of recombination between two genes is proportional to their physical distance.
Recombination between genes that are very closely linked is rare.
For genes that are very far apart on a single chromosome, the frequency of recombination is not proportional to their physical distance because recombination happens so frequently

8. Questions