Relationship between Genotype and Phenotype Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription replication RNA translation amino acid sequence protein function phenotype organism

Initiation at Origin of Replication Prokaryotes: Fixed origin DnaA proteins DnaB (helicase) Eukaryotes: Multiple origins ORC protein complex Cdc6 and Cdt1 MCM complex (helicase)

Refer to Figure 7-26 from Introduction to Genetic Analysis, Griffiths et al., 2015.

The Problem of Replicating Chromosome Ends telomere 3’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ A B A B A B RNA primer removal and DNA ligation + + DNA Replication 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ Last section of lagging strand cannot be primed. Result is a shorter chromosome after each round of replication.

The Problem of Replicating Chromosome Ends Here is another angle. Note again that the last section of lagging strand cannot be primed. A shorter chromosome is produced after each round of replication. It is theorized that as cells age (generations), telomeres shorten, eventually leading to their death. Is there a mechanism to maintain chromsome length?

Telomere Lengthening Telomerase (a reverse transcriptase) adds repeats to telomeric DNA. It carries an RNA molecule that serves as template for DNA synthesis. Refer to Figure 7-27 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Telomere Lengthening Refer to Figure 7-27 from Introduction to Genetic Analysis, Griffiths et al., 2015.

The Telomeric Cap Structure Telomeric end is protected by a “cap”. It consists of TRF1 and TRF2 (that bind to telomeric repeats) and proteins such as WRN* that bind to TRF1** and TRF2**. * Werner Syndrome protein ** TTAGGG Repeat Binding Factor Refer to Figure 7-28 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Relationship between Genotype and Phenotype Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

Making Recombinant DNA: Donor DNA Genomic DNA: DNA obtained from chromosomes of an organism Complementary DNA (cDNA): double-stranded DNA version of mRNA obtained by reverse transcription Chemically Synthesized DNA: DNA sequence obtained by automated chemical reactions