Set Study PDF

1. Directionality of RNA and DNA: Polymerases catalyzes formation of phosphodiester linkage between nucleotides. The DNA structure runs antiparallel: the two strands of the double helix run in the opposite direction to each other, with one strand at a 5’ to 3’ direction, the other strand is...

1. Directionality of RNA and DNA: Polymerases catalyzes formation of phosphodiester linkage between nucleotides. The DNA structure runs antiparallel: the two strands of the double helix run in the opposite direction to each other, with one strand at a 5’ to 3’ direction, the other strand is 3’ to 5’. The strand number refers to the 5 carbon and 3 carbon atoms making up the sugar-phosphate backbone. This is important for replication, transcription, and translation because the 5’ to 3’ direction ensures that there is an accurate sequence copy, ensuring that codons are translated the same way each time. 2. Purine which is Adenine-Thymine (A-T) bonds to pyrimidine which is cytosine-guanine (C-G) pairs have equal base-pair length, so the DNA helix has the same 3-D structure regardless of the base sequence, so that the distance between the sugar-phosphate backbones remains consistent, maintaining DNA helix stability. 3. The structure of the nucleosome has a histone octamer wrapped around by the chromatin and an additional H1 histone holds the core together. The linker DNA connects adjacent nucleosomes. 4. Highly conserved DNA sequences are identical or very similar over long periods of evolutionary time. Species that have close relatedness of species usually share a high degree of gene sequence homology. One hypothesis for the conservation of these sequences is related to conserved gene products required for survival: that natural selection maintains conserved sequences by necessity. So mutations would not be conserved. The second hypothesis is that they were preserved due to slower rates of mutation in certain regions of DNA. 5. Cell proliferation is necessary for growth, cell replacement, and tissue repair. For example, growth in plant meristems and animal early-stage embryos. And skin in routine cell replacement and during wound healing. 6. Three subphases of interphase: G1 phase (first gap): cell growth, synthesizes proteins, and prepares for DNA replication. S phase (synthesis): DNA replication. G2 (second gap): replication of organelles. 7. Control of the cell cycle using cyclins: Cyclins are a family of regulatory proteins that control the cell cycle. The concentrations rise and fall during the cell cycle and a specific cyclin threshold is required to pass the cell cycle checkpoint. Cyclins bind to the cyclin-dependent kinases (CDK) which is an enzyme to form active complexes that can phosphorylate target protein that is necessary for events of the cell cycle. Phosphorylation can either active or deactivate a protein, it acts as an on/off switch to a protein by altering its structure through the addition of a phosphate group. 8. Consequences of mutations in genes that control the cell cycle leads to uncontrolled cell division which causes cancer as the genes that regulate the cell cycle, such as proto-oncogene which promotes cell growth and division when  mutated can become oncogene, leading to excessive cell proliferation and tumor suppressors when mutated can lose their ability to inhibit cell growth. 9. Differences between benign and malignant rumors: the rate of cell division and rate of cell growth differs as benign tumors have cells that are not cancerous and won’t spread. Malignant tumors has cells that are cancerous and the cancer will invade neighboring tissue and organs. For example, metastatic brain tumor, the primary tumor is where the cancer originated and the secondary tumors form when the cells from the primary tumor travel through the bloodstream or lymphatic system and establish somewhere else. 10. Gene expression is primarily controlled at the level of transcription by regulating the binding of RNA polymerase to a specific region of DNA called the promoter, which is facilitated by proteins called transcription factors that can bind to enhancer sequences on the DNA, ultimately determining how much mRNA is produced from a gene; this process allows cells to "turn on" or "turn off" specific genes depending on their needs by controlling the initiation of transcription. 11. Gene expression can also be controlled by regulating translation through the degradation of mRNA. As mRNA can persist from minutes up to days, before being broken down by nucleases, as mRNA provides the message required by the ribosomes for protein assembly, the longevity of the transcript will determine the expression levels of a gene. 12. The Genome contains all genetic information in DNA, including both coding DNA and non-coding DNA. Transcriptome has the set of all RNA transcripts including coding RNA which is the mRNA and non-coding RNA such as RNA, rRNA, and tRNAs transcription all essential for protein synthesis. The proteome is the set of all proteins. There are differences in gene expression because of the differentiation of cells. 13. Lactose influences the pattern of gene expression in prokaryotes. The Lac operon is a set of related genes for uptake and metabolism of lactose. When lactose is absent, the lac repressor inhibits transcription of the lac operon. It binds to the operator which partially overlaps with the promoter. This gets in the RNA polymerase’s way from transcribing the operon. When lactose is present, some molecules will convert to allolactose which binds to the lac repressor and creates a shape change so it can’t bind to the DNA. 14. Estradiol is a hormone steroid which is a lipid and is small and nonpolar meaning that it can pass through the lipid bi layer easily. It binds to a receptor in the cytoplasm. The hormone-receptor complex binds to a DNA sequence and causes the expression of specific genes. It affects the tissue by stimulating cell proliferation and differentiation. 15. DNA sequences are not altered by epigenetic changes so phenotype changes but not genotype is altered. Methylation of cytosine in the DNA of a promoter region causes transcription repressed. Methylation of amino acids in histone proteins can cause transcription to active or be repressed. 16. Phenotypic changes can be passed down without changes in nucleotide sequence. Meany’s work with rats found the effect of maternal care. High licking and lowlicking mothers on their rat pups created an epigenetic change that affected the next generation of pups, they copied their mother’s behavior. 17. Environmental effects on epigenetics: air pollution exposure results in a wide spread decrease in DNA methylation. 18. Imprinted genes are when you inherit only one working copy. Either the maternal growth gene or the paternal growth gene is silence. During the development of the sperm and eggs, most of the epigenetic markers within these gametes are erased to allow an embryo to differentiate. This leads to the genetic conflict hypothesis that imprinting grew out of a competition between males for maternal resources. Paternal imprinting favors large offspring, maternal prefers smaller offspring. Ligers have a lion father and tiger mother, big because the lion father prefers that and his gene couldn’t be suppressed by the maternal growth gene. For tigons, the male tiger and female lion, and is smaller because the female lion prefers it. 19. Monozygotic twins have identical DNA when there is a comparison of the epigenome as the twins grow older their epigenome diverged due to different lifestyles. 20. Mendel’s law of segregation is that during meiosis the two alleles of a gene separate from each other and each resulting gamete receives one allele for each gene. Due to random orientation of homologous  chromosomes, each gamete has a random chance of receiving either allele of each pair. 21. Mendel’s law of independent assortment states that the presence of an allele of one of the genes in a gamete doesn’t not influence which allele of another gene is present. If the genes are unlinked they are located on different chromosomes. 22. Radioactive isotopes of phosphorus and sulfur allowed Martha Chase and Alfred Hershey to conduct their experiment because they used 32P and radioactive protein 35S to determine that DNA and not the protein is the genetic material. 23. The results supported the conclusion that DNA is the genetic material because the radioactive protein coating wasn’t transmitted but the radioactive phosphorus in DNA was. 24. The results of Chargaff’s experiment showed that there was a fixed ratio of bases in each sample and there was always an equal amount of adenine and thymine as well as cytosine and guanine in each sample of DNA. This challenged the tetranucleotide hypothesis because different species had different numbers of base compositions not just four. 25. Knockout technology in gene editing which alters the genetic makeup of an organism to obtain a desired trait, an application of this is through Crispr-CAS9 which can be used to target specific gene and can remove or replace the knockout egen/.