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genetics chapter 6
DNA structure, replication, and recombination
| Question | Answer |
|---|---|
| purine | two ringed nitrogenous base |
| pyrimidine | singular ringed nitrogenous base |
| which bases are purines? which are pyrimidines? | adenine and guanine are purines, cytosine and thymine/uracil are pyrimidines |
| how are nucleotides connected within a DNA polymer? | phosphodiester bonds between the 3' carbon of one nucleotide and the 5' carbon of the next one. |
| How is DNA organized within a double helix? | the two chains of the double helix spiraling around an axis with the sugar-phosphate backbones on the outside and the flat pairs of bases meeting in the middle. |
| what is antiparallel? | the opposing orientation of the two DNA strands, one running in the 5' to 3' direction, while the other one runs in the 3' to 5' direction |
| major groove | the wider and deeper groove of the DNA spiral formed by the sugar-phosphate backbone on opposite sides of the molecule |
| minor groove | the narrower and shallower groove of the DNA spiral also formed by the sugar-phosphate backbone |
| significance of major and minor groove | they are crucial binding sites for proteins involved in DNA replication and transcription |
| how do base pairs bond between the different DNA strands? | hydrogen bonds, each nucleotide forms about two or three hydrogen bonds |
| A DNA | DNA structure that spirals to the right (right handed DNA) but is wider and shorter than B DNA |
| B DNA | DNA structure that spirals to the right (right handed DNA) |
| Z DNA | DNA structure that spirals to the left (left handed DNA) that takes on a zig zag shape |
| How do DNA binding proteins recognize different DNA bases when the double helix is intact? | by using hydrogen bonds and chemical interactions with the bases exposed in the major groove |
| Does RNA ever function as genetic material? | yes, in retroviruses (like viruses causing polio and AIDS) |
| Basics of DNA replication | DNA helicase unwinds two DNA strands forming replication forks. DNA polymerase moves in same direction as fork to synthesize DNA in leading strand. RNA primers synthesize DNA in okazaki fragments. DNA Polymerase I removes primers and Ligase joins O.F. |
| what is meant by semi-conservative replication? | copying in which one strand of each new double helix is conserved from the parent molecule and the other is newly synthesized |
| what provides the energy for DNA replication? | ATP is primary source of energy for DNA replication |
| replication fork | replication bubble with Y shaped area (unwinding of DNA strands) |
| okazaki fragments | small fragments of about 1000 bases placed on the lagging strand initiated by RNA primers made by primase |
| helicase role in DNA replication | unwinds the double helix |
| single stranded binding proteins role in DNA replication | binds to the separated strands of DNA to keep them from rebinding and stabilizing them |
| primase role in DNA replication | synthesizes RNA primers to begin replication and those primers initiate the okazaki fragments on lagging strand |
| DNA ligase role in DNA replication | covalently joins each okazaki fragment into a continuous strand of DNA |
| topoisomerase role in DNA replication | helps relax the supercoils by nicking one or cutting both strands of the DNA |
| telomeres | ends of a chromosome |
| how does crossing over occur at the molecular level? | breakage and rejoining of DNA strands between homologous chromosomes during prophase I of meiosis |
| what happens during crossing over? | homologous chromosomes exchange genetic material, resulting in new combinations of alleles |
| difference between crossover pathway and non-crossover pathway | crossover pathway results in exchange of genetic material between homologous chromosomes, forming new combinations of alleles. non-crossover pathway copies genetic info from one homologue to the other via gene conversion without exchanging large segments |
| branch migration | the process where a Holliday junction moves along a DNA sequence, exchanging base pairs between two homologous DNA strands |
| holiday junctions | resulting X structures in the double strand break repair model |
| gene conversion | the non-reciprocal transfer of genetic information from one DNA sequence (the donor) to another (the acceptor), often during meiotic recombination |
Created by:
angievelasco