Gaps where primer was are then filled by yet more complementary nucleotides. 9. To make sure there is no mistake in new DNA molecule the new strand is proofread. 10. Finally, enzyme called DNA ligase seal up the sequence of DNA into two continuous double strands.
This breaks the DNA loop. The two AraC-arabinose complexes bind to the aral1 and aral2 sites which promotes transcription. When arabinose is present, AraC acts as an activator. If arabinose is present, it builds a complex: AraC + arabinose This complex is needed for RNA polymerase to bind to the promoter and transcribe the ara operon. Also for activation the binding of another structure to aral is needed: CRP+cyclic AMP so the activation depends on the presence of arabinose and cAMP.
After isolation of DNA from the source it is digested enzymatically with the help of restriction endonucleases. Enzyme treated DNA is then separated by size in an agarose gel and shifted to a membrane. A radioactive or fluorescently labeled probe is bonded with the DNA on the membrane. They target specific sequences that are marked by the restriction enzyme sites. The size of these fragments varies hence generate a biological bar code of restriction enzyme- digested DNA fragments.
DNA also can directly repaired damaged bases. A repair enzyme recognizes incorrect structure in the DNA and directly converts it to a correct structure. Base exision repair involves a category of enzymes known as DNA-N-glycosylacases. The enzymes identify the damaged base and cleave the bond between it and the sugar in the DNA. Then it will remove one base, excises several around it and then replaces it with several new bases using DNA polymerase adding to 3’ ends and then closing it with ligase attached to 5’ end.
Epigenetics is a mechanism for mediating gene activity independent of DNA sequence determining which genes are turned on and which genes are turned off. (Holliday, 1994) This mechanism therefore plays a key role in the onset of many complex diseases, like for instance cancer. DNA methylation is a crucial epigenetic modification of the genome that is involved in regulating many cellular processes. Basically, DNA methylation
INTRODUCTION To divide, a cell must grow, replicate its genetic material (DNA), and split into two daughter cells. Cells perform these tasks in an organized series of steps that make up the cell cycle. In eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases: interphase and the mitotic (M) phase. • During interphase, the cell grows and makes a copy of its DNA. • The mitotic (M) phase, divides the cell DNA into two sets and its cytoplasm, forming two new cells.
Homologous recombination (HR) can be explained as a process where DNA is exchanged or copied between two chromosomes or different regions of the same chromosome. The process requires homology between the exchanging DNA regions. Homologous recombination repairs DNA breaks, especially double stranded breaks (DSBs), stabilizes and repairs stalled forks. HR consists of a series of inter related pathways that function in repair of DNA breaks (Figure 4). Initially, stretches of single stranded DNA (ssDNA) are resected at the stalled forks or DSB ends which are quickly bound by replication protein A (RPA).
To minimize the variation of sampling, the tissue specimens were taken by two of the authors (XXXXX and XXXX). The tissue samples were collected as previously described.11, 12 All tissue specimens were immediately immersed in RNAlater® solution (Qiagen, Germany) and then stored at -20 °C until RNA extraction. RNA extraction Total RNA was purified with an RNeasy® mini kit (Qiagen, Germany) following the manufacturer’s instructions. Tissue Lyser LT equipment (Qiagen, USA) was used in the mechanical lysis step. RNA concentration and quality were determined using a NanoDrop ND-1000 spectrophotometer (Thermo Scientifc, USA).
1. Write a sentence for each of these mechanisms describing the manner in which the DNA can be transferred from one cell to another. Transformation: During transformation pieces of genetic instructions are released by a bacterium. Another bacterium, picks up the DNA into its own genome. Bacteria taking up foreign DNA is known as transformation.
Student’s Name Professor’s Name Subject DD Month YYYY Question Answer Question 1: Section (a): Composition of Nucleosomes The nucleosome is the basic unit of the DNA and forms the building block of chromatin. Chromatin is a complex of the DNA and the cellular histone protein cores forming eukaryotic chromosomes. Structurally, the nucleosome core particle comprises 1.6 left-handed superhelical turns of DNA wound around a protein complex called the histone octamer, which consists of 2 copies each of the core histones attached to the central tetramer H3/H4. The latter is flanked by two H2A/H2B dimers (Kornberg 868). The histone octamer, therefore, is a set of the 8 basic proteins whose fundamental structure of a single molecule includes three