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DNA/RNA
| Question | Answer |
|---|---|
| What is DNA? | A double-stranded antiparallel polymer made out of nucleotides where the phosphate group of one nucleotide bonds with the deoxyribose of another nucleotide |
| Describe the sugar-phosphate backbone | Pentose sugars bonded with phosphate groups to form the backbone of a nucleic acid where nitrogenous bases extend from as phosphodiester bonds hold it all together |
| Is a phosphodiester bond ionic, covalent, metallic, or a hydrogen bond? | Covalent bond |
| What type of bond connects antiparallel nucleotides in DNA? | Hydrogen bond |
| Which nitrogenous bases are found in both DNA and RNA? Which are exclusive to DNA or RNA? | Both: Adenine, Guanine, Cytosine DNA: Thymine RNA: Uracil |
| Describe Chargaff’s Rule | In any species, the amount of adenine = thymine, and the amount of cytosine = guanine |
| Name the pyrimidines and purines | pyrimidines: cytosine, thymine, uracil purines: adenine, guanine |
| Describe the shape of pyrimidines vs purines | Pyrimidines - single ring Purine - double ring |
| How is DNA read (list two ways) | 5’ to 3’ or 3’ to 5’ |
| Why are DNA strands “antiparallel” | Each strand has the same chemical structure but they run in the opposite direction |
| How does the antiparallel structure help with function? | Enzymes of DNA replication can function, nucleotides can form complementary pairs using hydrogen bonds, DNA is more structurally stable |
| DNA is a double _ while RNA is a single _ | Helix |
| When and how does DNA synthesis happen in the cell cycle? | Identical DNA is synthesized before mitosis after the G1 phase. |
| List the 8 steps of DNA replication | Unzipping, stabilizing, priming, building, extending, replacement, gluing, proofreading |
| Name the enzymes involved in DNA replication | Helicase, topoisomerase, RNA primase, DNA polymerase, exonuclease, ligase |
| Describe the unzipping stage | Helicase unzips the double stranded DNA, separating it into two single strands by breaking the hydrogen bonds between complementary base pairs (Y shaped structure = fork) |
| Describe the stabilizing stage | Unwinding the DNA causes lots of tension, so topoisomerase helps relax the DNA from the supercoiled structure while single-stranded binding proteins attach to the strands to prevent rejoining. |
| Describe the priming stage | A starting point is created by RNA primase before DNA is replicated. This enzyme attaches an RNA primer to an exposed DNA base. DNA polymerase attaches here to prepare building the 2nd strand. |
| Describe the building stage | DNA polymerase builds new strands by adding DNA nucleotides one at a time. The new strand is created in 5' to 3' by following the old strand 3' to 5' |
| Describe the extending stage | Helicase moves along the DNA, unzipping more of it. DNA polymerase can only move in one direction, so a leading strand is made continuously toward the helicase while a lagging strand is made in Okazaki fragments |
| Describe the replacement stage | The RNA primers need to be removed from the new strand and replaced with DNA nucleotides. They are cut out with exonuclease and replaced using DNA polymerase. |
| Describe the gluing stage | The new strands must be "glued" together using ligase. The leading strand only requires one DNA nucleotide to be joined while Okazaki fragments in the lagging strand must be joined. |
| Describe the proofreading stage | DNA polymerase proofreads the new strand as exonuclease cuts out any irregular nitrogenous bases and replaced with DNA polymerase |
| Why is DNA replication "semi-conservative" | Each new DNA has half of the DNA from the parent and half of it being newly synthesized |
| What is the difference between DNA replication in eukaryotes and in prokaryotes | eukaryotes: DNA is linear and has multiple replication bubbles prokaryotes: DNA is circular and has only one origin of replication |
| Where does DNA synthesis occur? Where does protein synthesis occur? (Assume it is a eukaryote) | DNA synthesis - nucleus Protein synthesis - ribosomes in cytoplasm |
| Is RNA double stranded or single stranded? | Single stranded |
| What are the big three types of RNA? What are some smaller types and what are they? | Big types: mRNA, rRNA, tRNA RNA in viruses: genetic material ribozymes: catalyze various reactions as enzymes |
| What is mRNA | Messenger RNA - Disposable copy of DNA to carry instructions from the nucleus (used as a template to make proteins) |
| What is rRNA | Makes up ribosomes and assembles proteins on ribosomes |
| What is tRNA | Transfers amino acids to ribosomes to construct proteins as it matches amino acids to mRNA to make those proteins |
| Review: What roles do proteins have in the human body? | Cell transport, the immune system, hormonal responses, movement |
| Where does transcription and translation occur in eukaryotes in prokaryotes | Eukaryotes: transcription in nucleus, translation in cytoplasm Prokaryotes: transcription and translation in cytoplasm |
| What is the central dogma of biology | Genetic info used to perform functions goes from DNA to RNA to proteins in transcription and translation |
| What is the FUNCTION of DNA for the whole organism? | Genetic code that determines genetic characteristics for organisms |
| What are genes? | Sections of DNA that code for specific proteins |
| Can DNA or mRNA make proteins directly | mRNA |
| What is transcription? What is translation? | Transcription - mRNA is built using DNA template Translation - proteins are built using RNA |
| Describe how mRNA is initially made | DNA is unzipped, RNA polymerase attaches to a promoter sequence of DNA and adds complementary RNA nucleotides, messenger RNA strand is formed, RNA polymerase is done and mRNA strand released |
| Describe the later steps of transcription after mRNA is made | In eukaryotes, mRNA has non-coding regions called introns as they must be removed from the exons through splicing. A 5' cap on the 5' end and the poly A tail on the 3' end are placed to protect mRNA before leaving the nucleus through pores. |
| How does the direction change when converting from DNA to mRNA | 3' to 5' direction and then 5’ to 3’ |
| What is a codon? What is an anticodon? | A codon is a three-base code from the mRNA, the tRNA's three-base code is an anticodon as they are complementary to codons. |
| What is transported on the opposite end of a tRNA molecule? | Amino acid |
| Describe the steps of translation | mRNA attaches to a ribosome in cytoplasm, ribosome lines up tRNA molecules, anticodons match with codons on mRNA strand, tRNA carries amino acid, amino acid form peptide bonds to build a polypeptide strand, tRNA molecules detach and pick up new amino acid |
| What is gene regulation? | The ability of an organism to control which genes are transcribed in response to the environment |
| What is an operon? | A section of DNA that contains the genes for the proteins needed for specific metabolic needs that often controls the transcription of genes (prokaryotes) |
| What are hox genes? | Homeobox genes - determine the body plan for simpler multicellular organisms (like insects) where a mutation could affect the order of the structures |
| What is a mutation? | A random change in an organism's genetic material |
| What are mutagens? Give examples. | Factors that increase the risk of a mutation occurring (gamma rays, x-rays, UV light, chemical mutagens, tar) |
| What are the types of the causes of mutations? | Substitution - one base is swapped for another base Insertion - one or more bases are inserted into the DNA strand Deletion - one or more bases are removed from the DNA strand |
| What are the types of the effects of mutations? | Silent - no effect on any amino acids due to wobble effect Missense - isolated effect on one amino acid Frameshift - rest of amino acids get affected from that mutation Nonsense - early stop codon |
| What is the wobble effect? | Multiple codons code for some amino acids rather than just one |
| Are mutations always harmful | Mutations could be helpful, neutral, or harmful |
| What are HeLa cells? | Immortal cancer cells from Henrietta Lacks that have been used in scientific breakthroughs in medicine and laboratories despite the lack of consent |
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