Chromosomal LandscapesChromosomal Landscapes

Refer to Figure 1-7 from Introduction to Genetic Analysis, Griffiths Refer to Figure 1-7 from Introduction to Genetic Analysis, Griffiths etet alal., 2012. ., 2012.

Human Chromosomal LandscapesHuman Chromosomal Landscapes

Refer to Figure 1-8 from Introduction to Genetic Analysis, Griffiths Refer to Figure 1-8 from Introduction to Genetic Analysis, Griffiths etet alal., 2012. ., 2012.

Molecular Basis forRelationship between Genotype and Phenotype

DNA

RNA

protein

genotype

function

organismphenotype

DNA sequence

amino acidsequence

transcription

translation

replication

Replication of DNA is Replication of DNA is semiconservativesemiconservative. .

Each strand serves Each strand serves as a template.as a template.

The two strands The two strands separate from each separate from each other when other when hydrogen bonds hydrogen bonds are broken.are broken.

New strands are New strands are synthesized by the synthesized by the addition of addition of nucleotides with nucleotides with bases bases complementary to complementary to those of the those of the template.template.

DNA replication is DNA replication is discontinuousdiscontinuous..

Two identical double Two identical double helices result.helices result.

Replication of DNA is Replication of DNA is semiconservativesemiconservative. .

Each strand serves Each strand serves as a template.as a template.

The two strands The two strands separate from each separate from each other when other when hydrogen bonds hydrogen bonds are broken.are broken.

New strands are New strands are synthesized by the synthesized by the addition of addition of nucleotides with nucleotides with bases bases complementary to complementary to those of the those of the template.template.

DNA replication is DNA replication is discontinuousdiscontinuous..

Two identical double Two identical double helices result.helices result.

Refer to Figure 7-11 from Introduction to Genetic Analysis, Griffiths Refer to Figure 7-11 from Introduction to Genetic Analysis, Griffiths etet alal., 2012. ., 2012.

Refer to Figure 7-12 from Introduction to Genetic Analysis, Griffiths Refer to Figure 7-12 from Introduction to Genetic Analysis, Griffiths etet alal., 2012. ., 2012.

DNA DNA polymerization polymerization requires DNA requires DNA polymerase.polymerase.

Refer to Figure 7-15 from Introduction to Genetic Analysis, Griffiths Refer to Figure 7-15 from Introduction to Genetic Analysis, Griffiths etet alal., 2012. ., 2012.

DNA PolymerasesDNA Polymerases

At least 5 DNA polymerases are known in At least 5 DNA polymerases are known in E. E. coli coli ..

DNA polymerase I (pol I):DNA polymerase I (pol I):

• adds nucleotides in adds nucleotides in 55’’ to 3 to 3’’ direction direction• removes mismatched based in removes mismatched based in 33’’ to 5 to 5’’ direction direction• degrades double-stranded DNA in degrades double-stranded DNA in 55’’ to 3 to 3’’ directiondirection

DNA polymerase II (pol II):DNA polymerase II (pol II):

• repairs interstrand cross-linksrepairs interstrand cross-links

DNA polymerase III (pol III):DNA polymerase III (pol III):

• catalyzes DNA synthesis at replication fork in catalyzes DNA synthesis at replication fork in 55’’ to 3 to 3’’ direction direction and only adds nucleotides at 3 and only adds nucleotides at 3’’

end end of growing strandof growing strand

Overview of DNA SynthesisOverview of DNA Synthesis

DNA polymerases synthesize DNA polymerases synthesize new strands in 5new strands in 5’’ to 3 to 3’’ direction.direction.

Primase makes RNA primer.Primase makes RNA primer.

Lagging strand DNA consists Lagging strand DNA consists of Okazaki fragments.of Okazaki fragments.

In In E. coliE. coli, pol I fills in gaps in , pol I fills in gaps in the lagging strand and the lagging strand and removes RNA primer.removes RNA primer.

Fragments are joined by DNA Fragments are joined by DNA ligase.ligase.