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BIOLOGY GLOSSARY 3
Chapter 3 glossary terms
| Question | Answer |
|---|---|
| Adenine | one of the two purine nucleobases. Used in forming nucleotides of the nucleic acids. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stablising the nucleic acid structures. In RNA, adenine binds to uracil |
| Anticodon | the three nucelotides on a transfer RNA (tRNA) molecule that join in codons on mRNA my complementary base pairing during the process of translation |
| Antiparallel | running in opposite directions with one strand in the 5' to 3' direction, and the other in 3' to 5' direction (two strands of DNA molecules) |
| Base | one of the 5 nitrogenous chemicals present in the nucleotides of nucleic acids (DNA or RNA). These 5 bases are adenine, guanine, thymine, cytosine (DNA only), and uracil (RNA only) |
| Coding strand | the strand of DNA that has the same nucleotide base sequence as the mRNA strand produced by transcription (uracil in the mRNA in place of the thymine in DNA) |
| Codon | basic unit of the genetic code. A sequence of 3 nucleotides on mRNA that codes for a particular amino acid, or indicates the beginning or end of translation |
| Complementary base pairing | the pairing in DNA and RNA molecules of the nitrogenous bases between two strands. In DNA adenine always pairs with thymine, and cytosine with guanine |
| Constitutive genes | a gene or protein that is always expressed or active |
| Cytosine | a nitrogenous base (or prymidine) that occurs in nucleotides of DNA and RNA |
| Degenerate | more then one codon may code for a particular amino acid |
| Di-nucleotide | two nucleotides joined through a condensation polymerisation reaction that joins phosphate of one nucleotide to the 3' end of the other nucleotides sugar molecule. Water is removed in the process |
| Double helix | the double-stranded, coiled structure of a DNA molecule |
| Exon | the region of a gene that codes for a protein |
| Gene | a specific sequence of nucleotides that codes for a particular protein of RNA molecule. It is the unit of hereditary |
| Gene expression | the process that leads to the transformation of the information stored in a gene product (usually a protein or RNA structure) |
| Gene regulation | processes that control gene expression, turning genes on or off |
| Guanine | a nitrogenous base (or purine) that occurs in nucleotides of DNA and RNA |
| Induced | to promote or to activate. When a gene is induced its transcription is activated |
| Inducible operon | an operon that is under the control of regulatory proteins (transcription factors) |
| Intron | section of DNA that does not code for proteins and is spliced during mRNA processes in eukaryotes |
| Lac operon | contains the genes that code for three proteins involved in the metabolism of lactose in E. coli and a few other bacteria. It is an inducible operon and its genes are transcribed only when lactose is available |
| Lac repressor | a DNA-binding protein that binds to the operator site of the lac operon, inhibiting the transcription of the genes in it |
| LacI | a regulatory gene that codes for the lac repressor |
| Messenger RNA (mRNA) | RNA molecule transcribed from DNA in the nucleus, which passes into the cytoplasm and binds to a ribosome. At the ribosome, RNA is translated into a polypeptide |
| Nucleotide | monomer, or building block, of the nucleic acids DNA and RNA. Consists of a phosphate, a sugar, and a nitrogenous base |
| Operator | the segment of DNA that is the binding site of the transcription factor |
| Operon | a unit of DNA under the regulation of a single promotor that codes for several proteins |
| Phosphodrester bond | the bond that joins nucleotides into a chain of DNA and RNA by linking the phosphate group of one nucleotide and the sugar of another |
| Poly-A tail | a long trail of adenine nucleotides (100-250) that is added to the end of mRNA during processing. This increases the stability of the mRNA |
| Polynucleotide | a polymer of nucleotides joined together through a condensation polymerisation reaction. Can be DNA or RNA |
| Promoter | upstream region of a gene (a specific DNA sequence) to which RNA polymerisation attaches, initiating transcription |
| Protein synthesis | the production of a protein through the processes of gene expression, which, in eukaryotes, comprises of transcription, RNA processing, and translation |
| Purine | a nitrogenous base that has a double ring structure (adenine and guanine). Each purine base pairs with a specific pyrimidine base (cytosine, thymine and uracil) |
| Pyrimidine | a nitrogenous base that has a single ring structure (cytosine, thymine and uracil). Each pyrimidine base pairs with a specific purine base (adenine and guanine) |
| Regulatory gene | a gene that codes for transcription factors (which in turn control gene expression at the transcription stage) |
| Repressed | describes a gene that is inhibited and cannot be transcribed |
| Ribosomal DNA | a nucleic acid synthesised in the nucleolus that forms part of a ribosome |
| RNA polymerase | an enzyme that catalyses the synthesis of RNA, using an existing strand of DNA as a template |
| RNA processing | the removal of introns from the primary transcript produced in transcription. The exons are joined to form mRNA, ready for translation. This stage of gene expression occurs only in eukaryotes |
| Spliceosome | enzyme that removes the introns from the primary transcript produced in transcription. The exons are joined to form mRNA, ready for translation |
| Splicing | the removal of introns from the primary transcript to create mRNA during RNA processing (in eukaryotes) |
| Structural gene | a gene that codes for proteins and RNA molecules that are not involved in gene regulation (eg. enzymes) |
| TATA box | a name given to a common sequence of bases in eukaryotic genes, which it TATAAA, that codes for the promoter region |
| Template strand | a strand of DNA or RNA used as a template for building a complementary strand of a precise nucleotide sequence |
| Thymine | a nitrogenous base (pyrimidine) found in the nucleus of DNA |
| Transcription | process by which a base sequence in DNA is used to produce a base sequence in RNA |
| Transcription factor | proteins that control gene expression at the transcription stage by binding to DNA sequences close to the promoter region of a gene or to RNA polymerase to induce or repress the expression of specific genes |
| Transfer RNA (tRNA) | an RNA molecule that brings a specific amino acid to a ribosome so it can be joined to another amino acid during translation |
| Translation | the process in which the base sequence of a mRNA molecule is used to produce the amino acid sequence of a polypeptide |
| Triplet | sequence of the 3 nucleotides in DNA that carries the genetic information for the sequence of amino acids in a protein. Each triplet usually codes for one amino acid |
| Uracil | a nitrogenous base (purine) found in the nucleotides of RNA. It forms a base pair with adenine |
Created by:
emmawalton05
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