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.