Biology Flash Cards

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Biology Definitions

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Obligate Intracellular ParasiteAn "Obligate Intracellular Parasite" is a parasite that cannot reproduce outside an infected host cell. The parasite's reproduction is entirely dependent on hijacking mechanisms found within the infected cell. For example, viruses use the infected cells Ribosomes (and other cell organelles) to produce new viruses, thus reproducing.Virus, Ribosome, Translation, Transcription
Okazaki FragmentsThe lagging strand of DNA requires much more work to replicate than does the leading strand. Because the lagging strand is oriented from 5' to 3', and because its complement is oriented from 3' to 5', and because the growing complementary strand can only add nucleotides onto the 3' end, the new DNA strand is created by using many primers to create small, backward strands of DNA (Okazaki Fragments) which are then joined together with Ligase. Whereas the leading strand engages in continuous replication, the lagging strand engages in discontinuous replication, as represented by Okazaki Fragments.Lagging Strand, Leading Strand
Oligonucleotide probeA scientists wishes to find a particular gene in a DNA cloning library which contains all the genes of a particular genome. If the scientist knows the protein which the gene produces, she can guess all the possible different codon sequences which could be used to translate the first n amino acids of the protein. She could then generate strands of these oligonucleotide sequences, and use these as "probes". She would heat up the DNA cloning library's colonies in an autoclave to break apart the cells and release their DNA onto a filter. She would then expose the oligonucleotide probes to the filter, to see which probes "stick" to the filter as they bind to their complementary DNA strands (by Crick-Watson base pairing) which are attached to the filter, identifying the original colonies of bacteria (by their original location on the filter) which had the gene of interest. These probes are "labeled" in someway (e.g. radioactively).DNA Cloning
OligopeptideA sequence of approximately 10-15 amino acids. In proteins, the term is often used to specify an epitope (short sequence of amino acids that is recognized by the immune system as "foreign").Epitope
OncogeneA gene that can cause cancer. From the Greek root "onco', meaning tumor or lump.Rous Sarcoma Virus, Cancer Cells, SRC, Proto-Oncogene
Operator SequenceAnother name for "operator site".Operator Site
Operator SiteA site on a DNA sequence preceding an Operon, where a repressor molecules can bind and inhibit the transcription of the genes in the operon.Operon, Lac Operon
OperonSome bacteria have DNA segments that are transcribed into a single mRNA with multiple start sequences, allowing more than one protein to be translated from a single mRNA. Generally, these types of DNA sequences are regulated. This type of regulated DNA sequence, which result in a single mRNA with multiple transcripts, is known as an "Operon".Polycistronic Message, Lac Operon
Organelle"little organ"; Organelles are specialized structures within a cell that perform specific functions. The Golgi Apparatus, Endoplasmic Reticulum, and Mitochondria are examples of organelles within a cell.Golgi Apparatus, Endoplasmic Reticulum, Mitochondria
Origin of ReplicationThe point on a DNA molecule where replication begins. Replication, DNA
OverexpressedIf a cell has too many Growth Factor Receptors, we say the receptors are "overexpressed". A cell with too many growth factor receptors may become cancerous, as the overexpressed receptors send signals for the cell to grow and divide, regardless of the absense of Growth Factors or presense of Growth Inhibitors in the extra-cellular environment.Cell Cycle, Growth Factor, Cancer

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