Chapter 16 The Molecular Basis Of Inheritance

How does DNA replication transmit genetic information?

DNA replication allows for genetic information to be inherited from parent self to daughter cells by mitosis and from generation to generation starting with meiosis.

Transformation

Change in genotype and phenotype due to a simulation of foreign DNA

Bacteria phages and viruses

• Bacteriaphages-viruses that infect bacteria

• Viruses-DNA (sometimes RNA) enclosed by protective coat, often simple protein.

The structural model of DNA

• Found pairing was more specific and dictated by the base

• adenine (a) paired only with thymine(t)

• Guanine (g) paired only with cytosine ( c )

A model for DNA replication the basic concept

Semi conservative model, conservative model, dispersive model

• Semi conservative predicts each daughter molecule will have one old strand, derived or conserve from the parent molecule in 1 newly made strand.

• Conservative model the two parent stands rejoin

• Dispersive model each strand is a mix of old and new

DNA Replications

• Origins of Replication-where two DNA strands are separated, opening up a replication bubble.

• Proceeds in both directions from origin until the entire molecule copied

The start of DNA replication

• At the end of each bubble is a replication fork which is a wise shaped region where parental DNA stands are unwound

• Helicases on twist the double helix at replication forks

• Single strand binding proteins bind two and stabilize single stranded DNA

• Topoisomerase relieves the strain of twisting of the double helix by breaking swiveling and rejoining DNA strands

The three are enzymes/proteins

Synthesizing a new DNA strand

• Enzymes DNA polymerase is catalyze the elongation of new DNA at a replication fork. can only add nucleotides to the 3’ end of a growing DNA strand.

• EnzymesMost enable the nurses require a primer to which they can add nucleotides, which is synthesized by Primase.

Leading Strand

• DNA polymerase add nucleotides only to the 3’ end of a growing strand therefore it can long only in 5’ to 3’ prime direction

• along one strand, the DNA polymer synthesizes, a leading strand continuously moving toward the replication fork

Lagging strand

• To elongate the lagging strand, DNA polymerase must work away from the replication fork

• The lagging strand is synthesized as series of Okazaki fragments, which are joined together by DNA ligase

Telomere

is repetitive DNA at the end of the eukaryotic chromosomes DNA molecule.

• telomerase catalyzes the lengthening of telomeres in germ cells

Eukaryotic chromosomes

• DNA is precisely combined with proteins in a complex called chromatin

• Chromosomes fit into the nucleus through an elaborate multilevel system of packing

• Proteins called histones are responsible for the main level of DNA packing and interphase chromatin

Euchromatin and Heterochromatin

• (E)loosely packed chromatin

• (H)Highly condensed chromatin