NCSU BIO 183 Final Exam Definitions
Wild-type allele - ANS-In genetics, the phenotype or genotype that is characteristic of
the individuals of a species in a natural environment
Sex-linkage - ANS-A trait determined by a gene carried on the X chromosome and
absent on the Y-chromosome
Autosomes - ANS-Any eukaryotic chromosome that is not a sex chromosome; present
in the same number and kind in both males and females of any species
Barr body - ANS-A deeply staining structure, seen in the interphase of a cell of an
individual with more than one X chromosome, that is condensed and inactivated X; only
one X remains active in each cell later early embryogenesis
Testcross - ANS-A mating between a phenotypically dominant individual of unknown
genotype and a homozygous "tester", done to determine whether the phenotypically
dominant individual is homozygous or heterozygous for the relevant gene
Hemophilia - ANS-A medical condition in which the ability of the blood to clot is severely
reduced, causing the sufferer to bleed severely from even a slight injury. The condition
is typically caused by a hereditary lack of a coagulation factor
Maternal Inheritance - ANS-A mode of uniparental inheritance from the female parent;
for example, in humans mitochondria and their genomes are inherited from the mother
X-chromosome inactivation - ANS-A process by which one of the copies of the X
chromosome present in female mammals is inactivated. The inactive X chromosome is
silenced by its being packaged in such a way that it has a transcriptionally inactive
structure called heterochromatin
Bacteriophage - ANS-A virus that infects bacterial cells; also called a phage
Phosphodiester linkage - ANS-The linkage between the 3' carbon atom of one sugar
molecule and the 5' carbon atom of another, deoxyribose in DNA and ribose in RNA.
Strong covalent bonds form between the phosphate group and two 5-carbon ring
carbohydrates (pentoses) over two ester bonds
,Chargaff's rule - ANS-States that DNA from any cell of all organisms should have a 1:1
ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the
amount of guanine is equal to cytosine and the amount of adenine is equal to thymine
DNA polymerase - ANS-A class of enzymes that all synthesize DNA from a preexisting
template; all synthesize only in the 5' to 3' direction, and require a primer to extend
Chromatin - ANS-The complex of DNA and proteins of which eukaryotic chromosomes
are composed; highly uncoiled and will diffuse in interphase nuclei. condensing to form
the visible chromosomes in prophase
Semiconservative Replication - ANS-DNA replication in which each strand of the
original duplex serves as the template for construction of a total new complementary
strand, so the original duplex is partially conserved in each o the two new DNA
molecules
Polypeptide - ANS-A molecule consisting of many joined amino acids; not usually as
complex as a protein
Ribosomal RNA - ANS-A class of RNA molecules found, together with characteristic
proteins, in ribosomes; transcribed from the DNA in the nucleolus
Transcription - ANS-The enzyme-catalyzed assembly of an RNA molecule
complementary to a strand of DNA
Messenger RNA (mRNA) - ANS-The RNA transcribed from structural genes; RNA
molecules complementary to a portion of one strand of DNA, which retranslated by the
ribosomes to form protein
Pre-mRNA - ANS-An immature single strand of messenger ribonucleic acid (mRNA);
synthesized from a DNA template in the cell nucleus by transcription. This comprises
the bulk of heterogeneous nuclear RNA (hnRNA).
Genetic code - ANS-A set of rules defining how the four-letter code of DNA is translated
into the 20-letter code of amino acids, which are the building blocks of proteins; a set of
three-letter combinations of nucleotides called codons, each of which corresponds to a
specific amino acid or stop signal
, Spliceosome - ANS-In eukaryotes, a complex composed of multiple snRNPs and other
associated proteins that are responsible for excision of introns and joining of eons to
convert the primary transcript in to the mature mRNA
snRNPs - ANS-"Small nuclear ribonucleic proteins"; RNA-protein complexes that
combine with unmodified pre-mRNA and various other proteins to form a spliceosome,
a large RNA-protein molecular complex upon which splicing of pre-mRNA occurs
Alternative splicing - ANS-In eukaryotes, the production of different mRNAs from a
single primary transcript by including different sets of exons
Translation - ANS-The process by which a protein is synthesized from the information
contained in a molecule of messenger RNA (mRNA). During this process, an mRNA
sequence is read using the genetic code, which is a set of rules that defines how an
mRNA sequence is to be translated into the 20-letter code of amino acids, which are the
building blocks of proteins
Codon - ANS-A set of three adjacent nucleotides, also called triplet, in mRNA that
base-pair with the corresponding aniticodon of tRNA molecule that carries a particular
amino acid, hence, specifying the type and sequence of amino acids for protein
synthesis
Aminoacyl-tRNA synthetase - ANS-An enzyme that attaches the appropriate amino acid
onto its tRNA. It does so by catalyzing the esterification of a specific cognate amino acid
or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA
Degenerate code - ANS-A code in which several code words have the same meaning;
there are many instances in which different codons specify the same amino acid. A
genetic code in which some amino acids may each be encoded by more than one
codon
N-terminus or amino terminus of a polypeptide - ANS-The start of a protein or
polypeptide terminated by an amino acid with a free amine group (-NH2). By
convention, peptide sequences are written N-terminus to C-terminus, left to right in LTR
languages
C-terminus or carboxyl terminus of a polypeptide - ANS-The end of an amino acid chain
(protein or polypeptide), terminated by a free carboxyl group (-COOH)
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