Replication Fork In the DNA double helix Topolisomerase relieves the tension. When Helicase breaks down the hydrogen bonds replication begins. Replication can take place in 2 directions because of the replication bubble. The enzyme Primase synthesizes the RNA primers. There has to be primers to start the synthesis at the 3’ end of the new strands.
7. The figure to the right shows that injection of M-phase cytoplasm into an oocyte triggers the cell to enter mitosis. What would be the expected effect on cell division if cytoplasm from a G2-phase cell were injected into an M-phase cell? A. DNA replication would begin again. B. activation of all cyclin-CDK complex in the cell.
Describe each process (including differences between bacteria and eukaryotes) and explain the significance of the differences between replication and transcription When first going through DNA replication, the two strands of double helix unwind. Each strand is an outline for the formation of a new, complementary strand. DNA helicase enzymes hang along the DNA molecule, opening the double helix as they move. Once the strands are separated, helix-destabilizing proteins bind to single DNA strands, preventing re-formation of the double helix until the strands are copied. Enzymes called topoisomerases produce breaks in the DNA molecules and then reconnect the strands, relieving strain and effectively preventing tangling and knotting during replication.
This is the restriction enzyme and acts as “molecular scissors” cuts the two DNA chains at a specific area in the genome so that sections of DNA can be supplemented or detached. A piece of RNA known as guide RNA is the second key molecule. This consists of pre-designed RNA quite small in length sequence, consisting of about 20 bases, positioned within a longer RNA scaffold. The scaffold binds to DNA and the pre-designed sequence ‘guides’ Cas9 to the right part of the genome. ensuring that the Cas9 enzyme intersects at the right point in the genome.
You will not see it in this phase. The nuclear envelope is not destroyed but is re-used in telophase. -the breakdown of the nuclear envelope allows the microtubules from the mitotic spindle to access the chromosomes. -microtubules attach to kinetochore proteins. Kinetochores are the protein area of the centromere on each sister chromatid.
Transgenesis and Cloning Transgenesis is the process of inserting a gene from one source into a living organism that would not normally contain the inserted gene. The gene can come from the same species (called Cisgenesis) or from a different species entirely. To facilitate the transfer of genes from one organism to another, often a Transgenic Organism with Recombinant DNA is created: -The first step in creating an organism capable of carrying out the transformation process is to isolate the required gene. This is done so using Restriction Enzymes, which target a specific gene sequence. The gene is often cut with staggered ends, called “Sticky Ends” which only allow specific and complementary gene sequences bond by base pairing.
Marshall Nirenberg and Heinrich Matthaei used mRNA made up of repeating uracil nucleotides in a cell free extract. They obtained amino acid chains consisting of phenylalanine. What did they learn when they asked the question, ”What happens when mRNA made up of only cytosine, alanine, and guanine are placed in a cell free extract?” 10. Explain how the structure of tRNA helps it to deliver the correct amino acid to the corresponding mRNA codon at the ribosome. Sketch the structure of a tRNA molecule, making sure to label the amino acid and the
Synthesis, processing, and functionThe brief existence of an mRNA molecule begins with transcription and ultimately ends in degradation. During its life, an mRNA molecule may also be processed, edited, and transported prior to translation. Eukaryotic mRNA molecules often require extensive processing and transport, while prokaryotic molecules do not. [edit] TranscriptionMain article: Transcription (genetics) Transcription is when DNA makes RNA. During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed.
A polynucleotide has a free phosphate group at one end and a free OH group at the other end. Structure of DNA: The main features of the three-dimensional structure of DNA are: • DNA is double-stranded, so there are two polynucleotide stands alongside each other. • The two strands are wound round each other to form a double helix. • The two strands are joined together by hydrogen bonds between the bases. The bases therefore form base pairs, which are like rungs of a ladder.
D) One strand is positively charged and the other is negatively charged. E) One strand contains only purines and the other contains only pyrimidines. 17) It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following? AA A) sequence of bases B) phosphate-sugar backbones C) complementary pairing of bases D) side groups of nitrogenous bases E) different five-carbon sugars 37) What is the function of DNA polymerase III? CC A) to unwind the DNA helix during replication B) to seal together the broken ends of DNA strands C) to add nucleotides to the end of a growing DNA strand D) to degrade damaged DNA molecules E) to rejoin the two DNA strands (one new and one old) after replication 30) Eukaryotic telomeres replicate differently than the rest of the chromosome.