DNA
A molecule that all living organisms carry in almost every cell in their body. It contains instructions for the functions of every cell. We leave a trail of it behind us in the form of saliva, hair, blood, skin cells, etc.
nucleic acid
a macromolecule that stores information
nucleotides
individual units that make up DNA, which have 3 components: a molecule of sugar, a phosphate group (containing 4 oxygen atoms bound to a phosphorous atom), and a nitrogen-containing molecule called a base.
base
a nitrogen-containing molecule that helps make up each nucleotide.
What makes the backbones of the DNA molecule?
two alternating molecules: a sugar, then a phosphate group, and so on. The sugar is always deoxyribose and the phosphate group is always the same. These make up the sides of the chain. The sugar-phosphate backbone serves only to hold the bases in sequence
Adenine, thymine, cytosine, and guanine
the four nitrogen-containing bases that form pairs with each other on the DNA molecule.
base pairs
pairs joined via hydrogen bonds to join the two backbones of the DNA ladder together. The bonds are GC and AT. Because of this DNA has the same # of each base, and if we know the sequence for one strand in a dna molecule then we also know the other. This
code
the sequence in which bases appear in a molecule of an organism's DNA creates this, which holds the detailed instructions for the building of an organism- mainly in the form of instructions for the amino acid sequences of polypeptides.
genome
the full set of DNA in an individual organism. Contained within circular pieces of DNA in prokaryotes and long linear strands in the nuclei of eukaryotes.
chromosomes
small, manageable pieces of DNA in eukaryotes. Humans have 46 made from 23 unique pieces, one from our mother and one from our father. Circular in prokaryotes and linear in eukaryotes. Together they make up the organism's genome. They vary in length and c
locus
the location of a gene on a chromosome
gene
a specific sequence of base pairs/ DNA, on average about 3000 bases long, that contains all the necessary information to make all or part of a protein molecule/functionary product/polypeptide/RNA molecule.
alleles
different versions of a gene that code for the same trait. Within a species, individuals sometimes have slightly different instruction sets for a given protein, and these instructions can result in a different version of the same characteristic.
trait
any single characteristic or feature of an organism
junk DNA
non-coding DNA found mostly in eukaryotic cells. In almost all eukaryotic species, the amount of DNA present far exceeds the amount necessary to code for all of the proteins in the organism. A huge proportion of the base sequences in DNA do not code for p
introns
Noncoding segments of nucleic acid that lie between coding sequences.
genotype
the genes that an organism carries for a particular trait. Like the recipe of a cookbook.
phenotype
the physical manifestation of the instructions/genotype. Like the cookie of the recipe.
transcription
a step in the process of how a gene(a sequence of bases in a section of DNA) affects a phenotype- in which a copy of a gene's base sequence is made into a middle man called mRNA
translation
a step in the process of how a gene(a sequence of bases in a section of DNA) affects a phenotype- in which the produced copy is used to direct the production of a polypeptide, which then, in response to a variety of factors, including the cellular environ
mRNA
Messenger RNA. The middleman during transcription, which copies the base sequence/code and then moves out of the nucleus into the cytoplasm, where translation allows the messages encoded in it to be used to build proteins
Recognize and Bind
the first step in transcription. The enzyme RNA polymerase recognizes a promoter site and then binds to the DNA molecule at the promoter site and unwinds it just a bit, so that only one strand of the DNA can be read.
promoter site
a sequence in a gene that indicates the start of the gene
Transcribe
the second step in transcription. As the DNA is processed through the RNA polymerase, the RNA polymerase builds a copy or (transcript) of the gene from the DNA molecule called mRNA which once created can move elsewhere in the cell and its message can be t
Terminate
the third step in transcription. When the RNA polymerase encounters a sequence of bases on the DNA at the end of the gene (called a termination sequence), it stops creating the transcript and detaches from the DNA molecule. After this, the mRNA molecule i
Capping and editing
the fourth step in transcription. In prokaryotic cells, once an mRNA transcript is produced and begins to separate from the DNA it is ready to be translated into a protein (it doesn't have a nuclear membrane to cross). In eukaryotes, mRNAs receive extra p
ribosomal subunits
components of ribosomes, the protein-production factories where amino acids are linked together in the proper order to produce the protein.
What has to happen in the cytoplasm for translation to occur?
There must be large numbers of free amino acids floating around, ribosomal subunits, and molecules that can read the mRNA code and translate that message from a sequence of bases into a protein.
transfer RNA (tRNA)
molecules that translate the mRNA code by linking specific bases on the mRNA with specific amino acids that will be used to build a protein.
codon
each three-base sequence in mRNA. They each match with a tRNA molecule that carries a particular amino acid.
recognize and initiate protein binding
the first step in the translation of an mRNA molecule into a sequence of amino acids that will then fold into the complex 3D shape of a protein. The "start sequence" of the mRNA - signified by the bases A, U, and G - is recognized by a corresponding tRNA
elongate
the second step in the translation of an mRNA molecule into a sequence of amino acids that will then fold into the complex 3D shape of a protein. As the ribosomes moves along the strand of mRNA, each new amino-acid-carrying tRNA molecule binds to the next
protein synthesis
the process of progressively linking together the amino acids specified by an mRNA strand
terminate
the third step in the translation of an mRNA molecule into a sequence of amino acids that will then fold into the complex 3D shape of a protein. Once the ribosome encounters the three-base "stop sequence", protein assembly is complete. Translation ends, a
gene expression
the production of the protein that the gene's sequence codes for.
gene regulation
whether a gene is turned on - producing its protein product - or turned off. Usually hinges on environment.
operon
a group of several genes, along with elements that control their expression as a unit, all within one section of DNA. Consists of a promoter, an operator, genes, and regulatory genes.
promoter
the region of DNA that RNA polymerase recognizes and binds to in order to produce an mRNA transcript of the genes
operator
the region of DNA that a repressor protein can bind to and, by doing so, block RNA polymerase from transcribing the genes
regulatory genes
these genes- which can be located within the operon, near the operon, or elsewhere in the genome- code for repressor proteins that impede transcription or activator proteins that enhance transcription
positive control
a form of transcription regulation in which activators can initiate or speed up gene expression and enhancer sequences can speed RNA polymerase binding and gene transcription
negative control
a form of transcription regulation in which repressors can block or slow down gene expression and chemicals can bind to DNA and block gene transcription
post-transcription regulation
a mechanism of regulating gene expression in which mRNA processing, transport, and enzymatic breakdown can be blocked or accelerated and mRNA translation and protein processing rates can be altered
mutation
an alteration to the sequence of bases in an organism's DNA. This can lead to changes in the structure and function of the proteins produced.
point mutation
a type of mutation in which one base pair in the DNA is substituted for another, or when a base pair is inserted or deleted. Insertions and deletions can be much more harmful than substitutions, because they can alter the reading frame for the rest of the
chromosomal abberation
a type of mutation in which there are changes to the overall organization of the genes on a chromosome. This can involve the complete deletion of an entire section of DNA, the relocation of a gene from one part of a chromosome to elsewhere on the same chr
spontaneous mutations
mutations that arise by accident as long strands of DNA are duplicating themselves- at the rate of over 1000 bases a minute in humans- when cells are dividing. Most errors are corrected by DNA repair enzymes but some slip through.
radiation-induced mutations
mutations induced by radiation with enough energy to disrupt atomic structure- even break apart chromosomes- by removing tightly-bound electrons. non-ionizing radiation can damage DNA as well. Examples are UV rays and nuclear power plants.
chemical-induced mutations
mutations induced by chemicals which react with the atoms in DNA molecules.
the pathway from mutation to illness
1.) a mutated gene codes for a non-functioning protein, commonly an enzyme. 2.) the non-functioning enzyme can't catalyze the reaction as it normally would. 3.) The molecule it would have reacted with accumulates. 4.) The accumulating chemical causes sick