Bio 105 sestero montevallo exam 3 Questions And Answers

Describe the general structure of a nucleotide and the structure of a DNA molecule. - ANS dna- a polymer of nucleotides nucleotide- deoxyribose (5-carbon sugar) phosphate bound to 5 of the sugar Nitrogenous base bound to the 1' carbon of the sugar i.Purine: adenine (A), guanine (G) ii.Pyrimidine: thymine (T), cytosine (C) How are neighboring nucleotides linked together in a DNA strand? - ANS covalent phosphodiester bond What role does the order of nitrogenous bases in a DNA strand have in the storage of genetic information? - ANS Base order is "random" and the order of the bases provides for the storage of genetic information and makes sugar phosphate backbone Describe the association of the two DNA chains that form a double helix. - ANS chain is directional : The 5ʹ′ end has a 5ʹ′ carbon attached to a phosphate and the 3ʹ′ end has a 3ʹ′ carbon attached to a hydroxyl group What type of bond links bases of opposite strands? - ANS hydrogen bonding How are the two DNA chains that comprise a double helix complimentary? How do Chargaff's Rules reflect this characteristic of a DNA double helix? - ANS The base sequence of one strand can be determined from the base sequence of the other strand. Chargaff's Rules:# of purines= #of pyrimidines; # of A = # of T; and # of G = # of C Define: antiparallel strands. How is 5'→3' and 3'→5' orientation defined in DNA strands? - ANS strands run in opposite directions. chains wind into a helix,with the sugar-phosphate backbones of the two chains forming the outside of the helix. semiconservative DNA replication. - ANS Each strand of aDNA molecule is used as a template to synthesize a new strand so that daughter molecules are made of one "old" strand and one "new" strand. DNA helicase - ANS Enzyme that unwinds and unzips the DNA double helix. Single-stranded binding (SSB) proteins - ANS Proteins that bind to separated DNA strands to permit them from reattaching to each other. Topoisomerase - ANS Enzyme that removes supercoils that form as the DNA double helix unzips and unwinds. DNA primase - ANS Enzyme that makes an RNA primer of the DNA template. RNA primer - ANS short piece of RNA that is synthesized at the point where DNA replication begins DNA polymerase - ANS Enzyme that adds nucleotides to the 3' end of the new DNA strand. DNA ligase - ANS enzyme thatlinks newly formed segments of DNA. In what direction are nucleotides added to newly synthesized chains during DNA replication? In what direction is a template DNA strand read during replication? - ANS 5 to 3 3 to 5 How does the replication process differ on the leading strand of a DNA double helix vs. the lagging strand of the helix? Define: Okazaki fragments - ANS One newDNA strandgrows toward the replication fork andis made continuously (leading strand). iv.One new DNA strand grows away from the replication fork and is made in fragments (lagging strand). a.Okazaki fragments:Short DNA fragments initiated by RNA primers that result from lagging strand replication. How are newly synthesized DNA strands proofread for errors? How are these errors corrected? - ANS Mismatch repair:Special enzymes recognize incorrectly paired nucleotides and remove them; DNA polymerases fill in missing nucleotides. Nucleotide excisionrepair:removes and replacesDNA lesions (deformed DNA) caused by the sun's ultraviolet radiation or by harmful chemicals Telomeres - ANS Repeated DNA sequences at the ends of eukaryotic chromosomes. Chromosomes - ANS eukaryotic chromosomes are located in the nucleus; different species vary in chromosome size and number chromatin - ANS DNA + associated proteins sister chromatids - ANS Identical copies of a chromosome; full sets of these are created during the S subphase of interphase. Centromere - ANS Area where the chromatids of a chromosome are attached kinetochore - ANS A specialized region on the centromere that links each sister chromatid to the mitotic spindle. How much of a cell's life is spent in interphase compared to M phase - ANS Phase where the cell spends most of its life. Describe the events that occur and the characteristics of the cell during each phase of interphase (G1, S, G2). - ANS Which events characterize the M phase? What must take place before a cell enters M phase? - ANS prophase - ANS first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus Metaphase - ANS second phase of mitosis, during which the chromosomes line up across the center of the cell Anaphase - ANS Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell Telophase - ANS After the chromosome seperates, the cell seals off, Final Phase of Mitosis. Cytokinesis - ANS division of the cytoplasm How does cytokinesis differ in animal cells and plant cells? - ANS Plant and animal cells both undergo mitotic cell divisions. Their main difference is how they form the daughter cells during cytokinesis. During that stage, animal cells form furrow or cleavage that gives way to formation of daughter cells. Due to the existence of the rigid cell wall, plant cells don't form furrows. Detail the type of cell that is the end result of mitosis. - ANS Each daughter nucleus receives exactly the same number and kinds of chro mosomes that the parent cell possessed. homologous chromosomes - ANS Chromosomes that have the same sequence of genes and the same structure chromosome set - ANS a group of chromosomes that carries the basic set of genetic information of a particular species