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4U Biology
Molecular Genetics
| Question | Answer |
|---|---|
| complementary base pairing | G---C; A--T or A--U |
| antiparallel | complementary DNA strands are built in opposite directions |
| nucleotide | made up of 3 parts: phosphate group, a ribose sugar and a nitrogenous base |
| 5' to 3' | direction the strand is built. The 5th and 3rd carbons of the ribose sugar are bonded to a phosphate group (linked by phosphodiester bonds). The 1st carbon of the sugar is bonded to the nitrogenous base (linked by a glycosyl bond) |
| hydrogen bonds | these connect the 2 strands of DNA. There are 3 HB between G and C whereas there are 2 HB btwn A and T (or A and U) |
| nucleic acids | polymers of nucleotides (eg DNA, RNA, NAD+, FAD, NADP etc) |
| RNA | single strand nucleic acid where the nitrogenous base Uracil replaces Thymine |
| Purines | double ringed nitrogenous bases eg. Adenine and Guanine |
| Pyrimidines | single ringed nitrogenous bases eg Thymine, Cytosine and Uracil "pyrimi-ding is a single ring" |
| DNA | carries the genetic code; blueprint for all proteins |
| mRNA function | copy of 1 segment of DNA (1 gene long); carries info on how to make 1 specific protein from nucleus to ribosomes |
| DNA polymerase I | RNA primers are removed and replaced with DNA by this enzyme |
| Helicase | enzyme that opens up the DNA at the replication fork. |
| SSBs | proteins that coat the DNA around the replication fork to prevent rewinding of the DNA. |
| primase | enzyme that synthesizes RNA primers complementary to the DNA strand. |
| DNA polymerase III | enzyme that extends the primers, adding on to the 3' end, to make the bulk of the new DNA. |
| Ligase | The gaps between DNA fragments are sealed by this enzyme |
| Leading strand | this is a new strand of DNA, complementary to the template strand. It is build continuously towards the replication fork from the 5' to 3' direction. |
| Lagging strand | This new strand of DNA is built in fragments, called Okazaki fragments. |
| Transcription | This is the first step in gene expression. It involves copying a gene's DNA sequence to make an RNA molecule. |
| mRNA transcript | This carries the information needed to build a polypeptide (protein or protein subunit). |
| Initiation | RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription. |
| Elongation | One strand of DNA, the template strand, acts as a template for RNA polymerase. As it "reads" this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5' to 3' |
| Termination | Sequences called terminators signal that the RNA transcript is complete. Once they are transcribed, they cause the transcript to be released from the RNA polymerase. |
| pre-mRNA processing | Strands must have their ends modified, by addition of a 5' cap (at the beginning) and 3' poly-A tail (at the end). Also, parts of the pre-mRNA (called introns) are chopped out, and the remaining pieces (called exons) are stuck back together. |
| Translation | In this stage, the mRNA is "decoded" to build a protein (or a chunk/subunit of a protein) that contains a specific series of amino acids. |
| tRNA | These connect mRNA codons to the amino acids they encode. One end of each tRNA has a sequence of three nucleotides called an anticodon, which can bind to specific mRNA codons. The other end of the tRNA carries the amino acid specified by the codons. |
| Ribosomes | The structures where polypeptides (proteins) are built. They are made up of protein and rRNA |
| Epigenetic Control | This level involves modifying the DNA structure—without changing the sequence—to make it more or less accessible to transcription machinery. It involves DNA methylation or histone modifications. |
| Transcriptional Control | This is the most common form of regulation (enhancing or repressing). eg. Specific transcription factors bind to enhancer regions of DNA, which then interact with the promoter to increase the rate of transcription of a gene, |
| Post-Transcriptional/RNA Processing Control | pre-mRNA is modified before it is exported from the nucleus to the cytoplasm for translation. This includes splicing, capping, and the addition of a poly-A tail. |
| Translational/Post-Translational Control | This regulates how much mRNA is translated into protein. Post-translational control involves modifying the protein after it has been made. |
Created by:
jcepella