AP1Lec Study Guide 4 PDF
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Uploaded by EverlastingWetland7344
Palm Beach State College
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This document is a study guide on DNA, RNA, and protein synthesis. It explains the key processes and components involved, including transcription and translation. It covers fundamental concepts in molecular biology and genetics, ideal for undergraduate courses.
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Module 4 Study guide 1. The essential function of DNA is to code for the Proteins a cell synthesizes. 2. DNA is not Naked in the cell. It is complexed with proteins to form a fine filamentous material called Chromatin. Human chromatin consists of 46 long filaments called Chromosomes. 3. DNA and othe...
Module 4 Study guide 1. The essential function of DNA is to code for the Proteins a cell synthesizes. 2. DNA is not Naked in the cell. It is complexed with proteins to form a fine filamentous material called Chromatin. Human chromatin consists of 46 long filaments called Chromosomes. 3. DNA and other nucleic acids are composed of polymers of nucleotides -. Each DNA Nucleotide is made up of a Sugar (Deoxyribose), Phosphate a group (PH2O4), and a Nitrogenous base (Pyrimidine or Purine). 4. The Naked structure of DNA resembles a spiral staircase; each sidepiece is a backbone composed of phosphate groups alternating with the sugar (deoxyribose). The nitrogenous bases form the steplike connections between the two backbones. The nitrogenous bases are grouped into either of two groups: Pyrimidines: (Cytosine (C), Thymine (T), and Uracil (U)), which are single Carbon, Nitrogen rings or Purines : (Adenine (A) and Guanine (G)), which are double Carbon, Nitrogen rings. 5. The law of Complementary Base Pairing allows prediction of the sequence of one strand if the other strand’s sequence is known. The rule to know is Adenine and Thymine form two hydrogen bonds with each other; Glymine and Cytosine form three hydrogen bonds (a Purine binds to a Pyrimidine). A to T, and G to C. 6. The When a cell is preparing to divide (Mitosis) it copies its entire nuclear DNA (during Interphase, S-Phase). Chromatin condenses and coil further (Prophase) into chromosomes, each chromosome is made up of two sister Chromatids that are so condensed and coiled they can be visible in a light microscope. 7. Ribonucleic acid (RNA) is produced in three types: messenger RNA (mRNA), Ribosomal RNA (rRNA), and Transfer RNA (tRNA). 8. RNA and DNA have significant differences, although both are nucleic acids. RNA is much smaller than DNA, ranging from 70 to 90 bases in tRNA to over 10,000 bases in the largest mRNA; DNA averages more than 100 million base pairs. RNA is a single nucleotide chain, not a double helix. The sugar in RNA is Ribose, not Deoxy, and thymine is replaced by Uricell. The essential function of RNA is to interpret the code in DNA and direct the synthesis of proteins. (DNA “codes for the production of” mRNA “codes for the production of” Proteins) Transcription Translation 9. Gene is an information-containing segment of DNA that codes for the production of a molecule of RNA, which in most cases goes on to play a role in protein synthesis. 10. The 46 human chromosomes come in two sets of 23 each, one set from each parent. All the DNA in one 23-chromosome set is called the Genome. 11. Each pair of chromosomes has same Genes, but different versions (alleles) exist 12. The body can make millions of different proteins, all from the same 20 amino acids, (9 or these are the essentials from diet) that are encoded by genes, made of just four Nucleotides (A, T, C, G), in a DNA Base Triplet-this will be a sequence of 3 DNA nucleotides that stands for one amino acid. 13. Messenger RNA contains a “mirror image” of each DNA base triplet, and this group of three bases is called a codon. 14. Transcription is the process by which DNA is copied into mRNA. When a gene is activated a mRNA copy is made in the nucleus, and the mRNA after this transcription, then migrates to the cytoplasm where Translation can occur. Transcription begins where RNA polymerase (enzyme that binds to the DNA and assembles the mRNA) recognizes the DNA base sequences TATATA or TATAAA, and this informs the RNA polymerase where to begin -RNA polymerase opens up the DNA helix about 17 base pairs at a time, reads base from one strand of DNA- makes corresponding mRNA: - Where it finds C on the DNA, it adds G to the mRNA - Where it finds A on the DNA, it adds U to the mRNA - Where it finds T on the DNA, it adds A to the mRNA - Where it finds G on the DNA, it adds C to the mRNA RNA polymerase rewinds the DNA helix behind it as it’s doing Transcription, the gene can be transcribed by several RNA polymerase molecules all at once. The RNA polymerase will reach a Terminator: base sequence at the end of a gene which signals polymerase to stop. The actual RNA transcribed here is a Pre-mRNA-immature RNA product. This pre-mRNA will have-_Exons -“sense” portions of the immature RNA, which will be Translated to protein. And the pre-mRNA will have-_Introns-“nonsense” portions of the immature RNA, that must be removed before Translation. Alternative splicing—removing the introns by RNA polymerase enzymes and splicing the exons together (in different orders) into a functional mRNA molecule, is how one gene can code for more than one protein. (this is why with our approximately 22,300+ genes in our genomes, we can produce millions of different proteins). 15. Translation is the process by which the language of nucleotides is converted into the language of amino acids. This process relies on Ribosomes, which are cytoplasmic granules, consists of two granular subunits, 1-large and 1-small, composed of ribosomal RNA (rRNA) and enzymes. They occur mainly in cytosol, on surface of rough ER, and nuclear envelope. Three components are needed for the process. - 1 The mRNA begins with a protein cap where a ribosome will begin translation. - 2 tRNA is a molecule that coils on itself to form an angular L shape that has a 3-nucleotide anticodon on one end, and a binding site for one amino acid on the other. - 3 Ribosomes (the two subunits come together only during translation) Translation occurs in three steps: - 1 Initiation starts when mRNA passes through a nuclear pore, tRNA with anticodon UAC pairs with the start codon AUG - 2 Elongation represents sequential ribosomal activity that increases the number of amino acids in the polypeptide chain. - 3 Termination is the process where the ribosome reaches a stop codon. This causes the release of the protein from the ribosome; the ribosome dissociates into two subunits that can reassemble at the same mRNA and start the process again. 16. Protein synthesis requires more than the primary sequence of amino acids. It also involves a process that folds and coils the protein chain into secondary and tertiary structures, and in some cases association with other protein chains (quaternary structure), or binding with other molecules. Chaperone proteins guide a new protein strand into its proper configuration. The Endoplasmic reticulum (ER) and the Golgi complex have important roles in protein processing and secretion. A protein assembled on the ER surface moves into the ER cisterna where it is modified by enzymes (posttranslational modification). The ER pinches off a bubblelike transport vesicle coated with clathrin that holds completed proteins. These transport vesicles may fuse and move to the Golgi complex. The cluster of vesicles fuses with the Golgi complex, releasing its contents into the Golgi cisterna. The Golgi complex modifies proteins further, often by adding carbohydrate chains. Some of the Golgi vesicles become lysosomes, while others become secretory vesicles that merge with the plasma membrane, releasing cell products by exocytosis. 17. Gene Regulation: Genes are regulated by a number of factors that turn them on or off as their products are needed. A good example of Gene regulation is the production of Casein (milk protein) by mammary glands. - The hormone prolactin binds to receptors in the plasma membrane of a mammary gland cell - The binding to receptors triggers activation of a regulatory protein (transcription activator) in the cytoplasm. - The regulatory protein moves into the nucleus and binds to DNA near the gene for casein (a protein). - This binding enables RNA polymerase to transcribe the gene, producing mRNA. - Casein mRNA moves to the cytoplasm and is translated by ribosomes on the rough-ER. - The Golgi complex packages casein into secretory vesicles. - The vesicles release casein outside the cells (exocytosis), and it becomes part of breast milk 18. DNA codes for RNA to make only Proteins. Compounds other than proteins are synthesized in cells and are made through the activity of enzymes, which are Proteins encoded by genes. For example, there is no gene for the steroid testosterone (which is considered a lipid), but a cell of the testis enzymatically converts cholesterol to testosterone if genes for the enzymes are activated. DNA codes for RNA and protein synthesis, but it indirectly controls the synthesis of a wide range of substances. 19. DNA Replication: Is necessary prior to cell division and is accomplished through complementary base pairing. -1. DNA, the double helix, unwinds from the histones -2. DNA Helicase, an enzyme, opens up a short segment of the helix, exposing the bases. The point where the DNA is opened is called the replication fork. -3. Molecules of DNA Polymoiraes match the exposed bases with complementary free nucleotides. The two strands are copied by separate DNA polymerase molecules moving in opposite directions. One DNA polymerase makes a long, continuous strand; the other makes short strands moving away from the replication fork, and these short strands are joined together by DNA ligase. Two new daughter DNA molecules are thus synthesized from the original parental molecule, and each daughter DNA consists of one old (conserved) strand in the helix and one newly synthesized strand in the helix. This process is therefore called semiconservative replication. -4. While DNA is synthesized in the nucleus, new histones are being synthesized in the cytoplasm and are transported into the nucleus for combination with each new DNA helix to make new nucleosomes. 20. The Cell Cycle: is the life cycle period from one cell division to the next. It has Interphase (G1, S, G2) and Mitosis (which has four phases: prophase, metaphase, anaphase, and telophase.) G1, the First Gap phase, the cell synthesizes proteins, grows, and carries out its tasks in support of the body. It’s the interval between cell division and DNA replication S, the Synthesis phase, is the period during which the cell makes a duplicate copy of its centrioles and its entire nuclear DNA. G2, the Second Gap phase, is a relatively brief interval during which the cell finishes replicating its centrioles and synthesizes enzymes that control cell division; it also checks replication for errors. (G-zero phase: Some cells cease to divide for days, years, or the rest of one’s life; these are said to be in G0-phase) Mitosis is the period during which a cell replicates its nucleus and then pinches in two to form two new daughter cells. (The 4 phases can be remembered with the mnemonic P-MAT) -Prophase- chromosomes shorten and thicken becoming compact rods, and then align in the middle of the cell and have two chromatids per chromosome. The nuclear envelope disintegrates, and the chromosomes are released into the cytosol. The centrioles sprout elongated microtubules called spindle fibers, which push the centrioles apart towards opposite ends of the cell. Some spindle fibers grow toward the chromosomes and attach to the kinetochore on each side of the centromere. The chromosomes are tugged back and forth moving them towards cell’s midline. -Metaphase - is the period during which on the midline of the cell, the aligned chromosomes, anchored by the mitotic spindle, await the signal to split apart. -Anaphase- is the cleaving of the centromere of each chromatid pair. After splitting apart, each chromatid is a daughter chromosome, One daughter chromosome migrates to one pole, and the other daughter chromosome to the opposite pole (Sister chromatids/daughter chromosomes are genetically identical, and so the daughter cells that result are genetically identical) -Telophase- the daughter chromosomes are clustered on each side of the cell. A new nuclear envelope forms and the chromosomes begin to uncoil, while the mitotic spindle vanishes. 21. Cytokinesis is the division of the cytoplasm into Two daughter cells, signs can be seen starting in Anaphase and overlaps telophase. The parent cell eventually pinches in two as the furrow is deepened, and the daughter cells enter interphase.