Biology Reference
In-Depth Information
Gene:
a functional part of DNA that encodes a protein or RNA molecule.
Gene Frequency:
the relative frequency (proportion) of a gene in a population.
Genome:
the entire haploid complement of DNA in a cell or organism. The human
genome comprises approximately 3.2 billion bp.
Genotype:
the particular set of alleles present in each cell. At any one locus the two
alleles define the genotype such that if there are only two alleles then there are three
possible genotypes (AA, AB, BB).
Haploid:
presence of one set of chromosomes in a cell and therefore containing one
copy of the genome. Cells such as egg cells and spermatozoa carry a haploid genome
and the Y chromosome and mitochondrial DNA are haploid.
Hardy-Weinberg Law (HW law):
a law stating that in an ideal population, the
frequencies of an allele will remain constant from one generation to the next.
Heterochromatin:
a highly condensed part of the chromosome which remains tightly
packed throughout the cell cycle and is predominantly non-coding.
Heterozygous:
having different alleles at any particular locus.
Homozygous:
presence of two identical alleles at a given locus.
Locus:
the physical position of a gene or section of DNA on a chromosome. The
plural of locus is loci.
Locus Drop Out:
the non-detection of both alleles at a given locus.
Low Copy Number PCR:
a more sensitive method of DNA profiling where the
number of cycles is increased in order to amplify amounts of DNA typically less
than 100 pg.
Low Template DNA PCR:
any process that aims to increase the sensitivity of DNA
testing in order to amplify amounts of DNA typically less than 100 pg.
Mitochondria:
small semi-autonomous organelles of the cell which are primarily
responsible for energy production. They have their own circular genome that is
16 569 bp in length in humans.
Mutation:
alteration in the DNA sequence. The most common form of a mutation
is a single base transition (see next page).
Oligonucleotide:
a short sequence of single-stranded DNA.
Phenotype:
physical form of an organism resulting from genetic traits and environ-
mental factors.
Polymerase Chain Reaction (PCR):
a process of enzymatic amplification of DNA
in vitro
.
