Incomplete Codominance not always all or none incomplete intermediate blend Ex flower color codominance share both traits Ex blood type Plieotropy Red flower white flower pink flower gene affects more than 1 trait Ex sickle cell anemia malaria resistance Quantitative Traits vary by degree Ex continuous traits Qualitative Traits vary by a gradient Linkage physical association among genes on the same chromosomes should not sort independently because they are on the same chromosome can change by crossing over but not if they are close together Sex Linkage genes are on X or Y chromosomes crossing over creates parental and recombinant gametes in X chromosomes Ex hemophilia A x linked recessive Hershey Chase Experiment determined whether protein or DNA is the genetic material by using virus genes radioactive DNA was inside the cell radioactive protein was outside Primary Structure sugar phosphate backbone 5 carbon sugar 5 3 Polar molecule nucleotides held together by phosphodiester bonds covalent bonds Secondary Structure double stranded anti parallel to one another Purines A G Pyrimidines C T Watson Crick double helix DNA Replication happens in the 5 3 direction S Phase of Cell Cycle takes approx 10 hours hydrogen bonds stabilize the secondary structure bonding between complementary bases causes strands to twist DNA replicates about 80 000 bases second we must copy and distribute the stored info between cells during growth cell division conserve it accurately with as few errors as possible Storage Copy Distribute First we need a primer RNA primer Uracil comes in instead of Thyamine DNA template match bases to form complementary strand unzip H bonds to open the double helix add single strand by binding proteins primase primer starts process leading strand lagging strand DNA Polymerase III can only add nucleotides to the 3 end Leading strand continuous only 1 primer needed elongates toward replication fork Lagging strand delayed always happening in fragments many primers needed elongates away from replication fork Okasaki fragments the top and bottom strands are both leading and lagging Helicase opens up the strands of DNA breaks H bonds between the bases binds at the replication fork sections of double stranded DNA single strand going in double strand going out Okasaki fragments DNA Polymerase Topoisomerase DNA Polymerase I DNA Polymerase III only adds new nucleotides to the 3 end Transmission Genetics vs Molecular Genetics molecules o DNA Synthesis Replication Making complete copies of DNA o o Transcription Translation Copying sections of DNA into RNA Converting RNA into amino acids Overview of DNA Synthesis Replication binds ahead of the replication fork breaks covalent bonds in the sugar phosphate backbone to keep it from supercoiling Transmission genetics focuses on inheritance patterns based on observable phenotypes o Tracking movement of chromosomes through meiosis and fertilization Molecular genetics focuses on the structure and regulation of genes as they are stored on information DNA synthesis is a massive challenge with respect to storage copying and accuracy We hold all the information required to build an organism within every cell We must copy and distribute the stored information between cells during growth cell division We must conserve that information content accurately with the fewest possible mistakes during storage copying and distribution Proteins Required for DNA Synthesis Helicase o Single strand DNA binding proteins Stabilizes single strand DNA o Catalyzes breaking of hydrogen bonds between base pairs to open the double helix Breaks and rejoins the DNA double helix to relieve twisting forces caused by the opening of the helix Topoisomerase o Primase o Catalyzes the synthesis of the RNA primer DNA Polymerase III o Extends the leading strand Sliding Clamp o Holds DNA Polymerase III in place during strand extension Removes the RNA primer and replaces it with DNA DNA Polymerase I DNA Ligase o o Central Dogma in Cell Context Catalyzes the joining of Okazaki fragments into a continuous strand DNA is found in the nucleus Protein synthesis takes place in the cytoplasm DNA RNA Protein The meaning of genotype in classical and molecular genetics Classical Genetics o We don t know details about alleles o We just know they are passed down and interact in certain ways Molecular Genetics o We know the actual sequence of an allele o Each different sequence is a different version of the gene allele Many different genetic sequences can lead to the same classical genetics patterns of inheritance Many mutations are a loss of function and there are lots of sequence changes that lead to loss of function Conceptual Translation If all the information is stored in DNA then we should be able to read it and predict the amino acid sequence that it codes for We just need to know some of the rules Following the Central Dogma of information flow o DNA is transcribed to mRNA o mRNA is translated to proteins amino acids DNA is transcribed to mRNA Build mRNA 5 3 using complementary bases Start transcribing with AUG on mRNA reading 5 3 Read to the end of the sequence for now mRNA is translated to proteins amino acids Read mRNA 5 3 in triplets codons beginning with start AUG Look up codons in genetic code table Finish with stop codon o o o o o o The Challenges of Transcription Accurately extract information from DNA o Unzip the double helix o Use complementary base pairings Uracil instead of Thyamine Work with a small piece of chromosome o Determine which DNA strand to read o Determine where to start and finish copying Know when to express a gene o Important for responding to environment cell specialization and development The Challenges of Translation Convert information from one format to another o Read nucleotide base order Generate amino acid sequence o Use complementary base pairing mRNA to tRNA Hold everything together in space and time so that recognition and bonding can occur o Need to bind to the mRNA correctly o Need to get several tRNAs in place at once and catalyze the peptide bonding o Need to know when to stop translating Prokaryote Information Flow In bacteria transcription and translation are tightly coupled Transcription happens first and then translation occurs o o Occur simultaneously Translation begins before transcription is even finished o Because there is no nucleus or barrier for where the information is held Coding strand 3 5 Eukaryotes Information Flow transcription and