BioG 103 Essay Outlines

BioG 103 Essay Outlines - BioG 103 Final Essay Outlines 1...

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BioG 103 Final Essay Outlines 1. Advantages of Sexual Reproduction: In stable environment when org is particularly well-suited to present environment Asexual reprod is selective; offspring have same phenotype, all well-suited to environment Asexual condition increases in frequency and asexual popn grows much faster than sexual one; all females produce daughters that give rise to more reproductive daughters. In sexual reprodn, ½ of popn are males that don’t produce offspring. Disadvantages; Evolutionary Dead-end o Meiotic recombination and crossing over --> genetic variation that natural selection acts on o When environmental conditions change, orgs can’t adapt o Don’t in resistance to disease b/c each individual has same alleles at specific gene loci unlike sexual reproducing orgs --> disease can wipe out whole popn 2. Primary molecules in order, how they interact Replication : DNA strand provides template for synthesis of new complementary strand. Summary: 2 DNA strands separate. Each parental strand serves as a template for nucleotides on a new complementary strand. Nucleotides are connected--> 2 daughter DNA strands w/ 1 parental, 1 new strand. Steps: I. @ origins of replication proteins attach to DNA. Strands separate, replication bubble forms. II. DNA polymerase III adds nucleotides to new DNA: DNA polymerase III continuously elongates DNA strands in 5’ to 3’ direction on leading strand. III. Lagging strand: a. DNA polymerase III elongates lagging strand by adding short Okazaki fragments that grow 5’ to 3’ to the primer. b. DNA poly III falls off. After 2 nd fragment primed, adds nucleotides until it reaches 1 st primer. Falls off. c. DNA pol I replaces RNA with DNA. d. DNA ligase joins Okazaki fragments on their sugar-Phosphate backbones. Transcription: Synthesis of mRNA under the direction of DNA. DNA acts as template for making sequence of RNA nucleotides. Steps: I. Initiation: RNA polymerase II binds to promoter w/help of transcription factors incl. TATA box bound to promoter. DNA strands unwind. II. Elongation: Polymerase adds RNA nucleotides in 5’ to 3’ direction to the DNA strand. After DNA strands re-form a double helix. III. Termination: Reach polyadenylation signal; cut mRNA free. mRNA transcript and RNA poly fall off. IV. In eukaryotes: RNA transcript modified (RNA splicing using sNRPs; addtion of 5’cap, poly-A tail, etc) before leaving nucleus Translation : Act. synth of polypeptide under direction of mRNA. Base seq of mRNA --> amino acid seq of protein Steps : I. Initiation : Small ribosomal subunit binds to mRNA molecule. tRNA with anticodon
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UAC pairs with start codon AUG on mRNA. Large ribosomal subunit binds to complex --> Transition Initiation Cplx, w/ tRNA in P site II. Elongation : Amino acids added one by one to the chain. tRNA base-pairs in A site. Peptide bond forms--> rRNA catalyzes that growing peptide chain attaches to new aa in
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BioG 103 Essay Outlines - BioG 103 Final Essay Outlines 1...

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