BIOL 1107 1st Edition Exam 2 Study Guide Lectures 10 14 Lecture 10 February 19 Interphase is an in between phase when the cell is not going through mitosis Chromosome replication occurs during interphase Interphase involving the parent cell includes the G 1 phase S phase and G2 phase G1 involves 4 un replicated chromosomes S phase is DNA synthesis replication and G2 is the check phase to make sure the cells are corrects and do not go to be divided into mutated cells Mitosis is the division of the nucleus of somatic cells which involves the separation of two sister chromosomes of the daughter cell Mitosis is divides into 5 phases 1 Prophase Chromosomes condense and spindle apparatus forms 2 Prometaphase Nuclear envelope breaks down 3 Metaphase Chromosomes complete migration to middle of cell 4 Anaphase Chromatids separate and are pulled to different sides of the cell 5 Telophase Nuclear envelope re forms Cytokinesis the division of the cell itself occurs after mitosis In animal cells the cleavage furrow divides and the cell plate divides in plant cells Meiosis is very similar to mitosis however it involves the division of gametes therefore only occurs in organisms that carry our sexual reproduction The sister chromatids line up differently side by side and the homologous chromosomes can cross over creating variation In Mitosis the sister chromatids separate following the same process as mitosis Lecture 11 February 21 DNA replication proceeds in both directions from 5 to 3 only adding a nucleotide to the 3 end because DNA had directionality Helicase is the enzyme responsible for opening and stabilizing the double helix by catalyzing the breaking of hydrogen bonds between the two DNA strands to separate them Then single stranded DNA binding proteins attach to the separate strands to prevent them from rebinding and another enzyme cuts then rejoins the strand to relieve tension DNA polymerase requires a primer in order to be synthesized An RNA primer is used instead of a DNA primer because RNA is single stranded therefore able to prime the single strand portion of the DNA Primase RNA polymerase synthesizes the RNA primer Primer is continuously added to the lagging strand which is synthesized as short discontinuous fragments called Okazaki fragments Eventually you will come to the end of the lagging strand with the primer leaving an un replicated end so in order to not lose the useful information telomerase enzymes come in to extend the un replicated end so you can finish off the lagging strand It creates a redundant sequence to protect coded sequence from destruction Lecture 12 February 24 DNA information storage goes to mRNA information carrier via transcription and then from mRNA to proteins active cell machinery via translation Different genotypes genetic coding may cause differences in phenotype gene expression The way you behave is a phenotype caused by different genotypes Alleles are an alternate expression of the same gene each gene having multiple alleles associated with it Most life forms start with the same start codon AUG with a stop codon Mutations any permanent change in an organisms DNA can be in the form of a point mutation involving a single base change or a chromosome level mutation which is the addition or deletion of chromosomes from the individual s karyotype Point mutations can be missense creating changes in the amino acid sequence of the encoded protein or silent mutations not changing the amino acid sequence because multiple sequences can code for the same amino acid Lecture 13 February 26 RNA is used as a template strand for DNA This RNA template is called the primary transcript The primary transcript in eukaryotes is not an mRNA until primary transcript is processed through RNA processing Initiation is the first phase of transcription In prokaryotes sigma a protein subunit binds to the polymerase to initiate transcription It guides the RNA polymerase to specific promoter sequences on the DNA template strand The cell controls transcription by not allowing certain sigma proteins to bind to the promoter once they bind they go on to promote transcription The end of initiation is seen by a loop in the strand no longer allowing the polymerase to move down the strand In eukaryotes a group of proteins called basal transcription factors bind to DNA promoter initiating transcription The end of initiation here is seen by a three signal sequence The transcription of eukaryotic genes generates a primary RNA transcript that contains exons and introns RNA processes go into the strand and cut out regions in the gene introns that are not necessary for the production of a particular protein via splicing leaving behind and reuniting the exons When done it goes from a primary transcript to mRNA Splicing can build different proteins by the same gene by introducing exons and introns into the gene The deleted protein is taken and a 5 cap is added to one end while a Poly A tail is added to the other end The 5 cap is recognized by a smRNA causing the 5 cap to serve as a recognition signal for the translation machinery The Poly A tail extends the life of an mRNA by protecting it from degradation tRNA is attached to an amino acid by ATP input Enzymes called aminoacyl tRNA synthstases charge the tRNA by catalyzing the addition of amino acids to tRNAs Lecture 14 February 28 Tight junctions hold and seal cells together and keep things out Desmosomes connect the cytoskeletons of the cell and gap junctions act as channels between cells for direct communications Hormones are small information carrying molecules secreted from cells that circulate the body and act on target cells far from the signaling center Signal receptors are bound to hormones and dictate which cell respond to a particular hormone