A hybrid cell containing small fragments of irradiated human
chromosomes. Maps of irradiation sites on chromosomes for
the human, rat, mouse, and other genomes provide important
markers, allowing the construction of very precise STS maps
indispensable to studying multifactorial diseases.
See also: sequence tagged
site (ORNL)
The score of an alignment, S, calculated as the sum of substitution
and gap scores. Substitution scores are given by a look-up table
(see PAM, BLOSUM). Gap scores are typically calculated as the
sum of G, the gap opening penalty and L, the gap extension penalty.
For a gap of length n, the gap cost would be G+Ln. The choice
of gap costs, G and L is empirical, but it is customary to choose
a high value for G (10-15)and a low value for L (1-2). (NCBI)
Procedure used to join together DNA segments in a cell-free
system (an environment outside a cell or organism). Under appropriate
conditions, a recombinant DNA molecule can enter a cell and
replicate there, either autonomously or after it has become
integrated into a cellular chromosome. (ORNL)
The process by which progeny derive a combination of genes
different from that of either parent. In higher organisms,
this can occur by crossing over.
See also: crossing over, mutation
(ORNL)
Regulatory region or sequence
A DNA base sequence that controls gene expression. (ORNL)
Repetitive DNA
Sequences of varying lengths that occur in multiple copies
in the genome; it represents much of the human genome. (ORNL)
A protein that recognizes specific, short nucleotide sequences
and cuts DNA at those sites. Bacteria contain over 400 such
enzymes that recognize and cut more than 100 different DNA
sequences.
See also: restriction
enzyme cutting site (ORNL)
Restriction fragment length polymorphism
(RFLP)
Variation between individuals in DNA fragment sizes cut by
specific restriction enzymes; polymorphic sequences that result
in RFLPs are used as markers on both physical maps and genetic
linkage maps. RFLPs usually are caused by mutation at a cutting
site.
See also: marker, polymorphism
(ORNL)
A specific nucleotide sequence of DNA at which a particular
restriction enzyme cuts the DNA. Some sites occur frequently
in DNA (e.g., every several hundred base pairs); others much
less frequently (rare-cutter; e.g., every 10,000 base pairs).
(ORNL)
Retroviral infection
The presence of retroviral vectors, such as some viruses,
which use their recombinant DNA to insert their genetic material
into the chromosomes of the host's cells. The virus is then
propogated by the host cell. (ORNL)
Reverse transcriptase
An enzyme used by retroviruses to form a complementary DNA
sequence (cDNA) from their RNA. The resulting DNA is then inserted
into the chromosome of the host cell. (ORNL)
The five-carbon sugar that serves as a component of RNA.
See also: RNA, deoxyribose
(ORNL)
Ribosomal RNA (rRNA)
A class of RNA found in the ribosomes of cells. (ORNL)
Ribosomes
Small cellular components composed of specialized ribosomal
RNA and protein; site of protein synthesis.
See also: RNA (ORNL)
Risk communication
In genetics, a process in which a genetic counselor or other
medical professional interprets genetic test results and advises
patients of the consequences for them and their offspring. (ORNL)
A chemical found in the nucleus and cytoplasm of cells; it
plays an important role in protein synthesis and other chemical
activities of the cell. The structure of RNA is similar to that
of DNA. There are several classes of RNA molecules, including
messenger RNA, transfer RNA, ribosomal RNA, and other small
RNAs, each serving a different purpose. (ORNL)
