Page |1
Lewin's Genes XII Adv. Molecular Bio Lewin's
Genes XII Composite 011
sRNA - ans-A small bacterial RNA that functions as a regulator of gene expression.
CRISPRs - ans-Clusters of regularly interspersed short palindromic repeats in
prokaryotes that are transcribed and processed into short RNAs that function in
RNA interference.
microRNA (miRNA) - ans-Small (21 to 23 nucleotides), evolutionarily conserved
noncoding RNAs that function in RNA silencing and posttranscriptional regulation
of gene expression. Bind to complementary sequences within the 3′ untranslated
region (UTR) of their target mRNAs and negatively regulate protein expression by
accelerating mRNA degradation and inhibiting mRNA translation.
RNA interference (RNAi) - ans-A process by which short 21- to 23-nucleotide
antisense RNAs, derived from longer double-stranded RNAs, can modulate
expression of mRNA by translation inhibition or degradation.
stRNA - ans-Short temporal RNA, a form of miRNA in eukaryotes that modulates
mRNA expression during development.
piRNA - ans-Piwi RNA, a special form of miRNA found in germ cells.
siRNA - ans-Short interfering RNA, an miRNA that prevents gene express
, Page |2
Kinetochore - ans-A small organelle associated with the surface of the centromere
that attaches a chromosome to the microtubules of the mitotic spindle. Each
mitotic chromosome contains two "sisters" that are positioned on opposite sides
of its centromere and face in opposite directions.
Telomere - ans-The natural end of a chromosome; the DNA sequence consists of a
simple repeating unit with a protruding single-stranded end.
T-loop - ans-Structure characterized by a series of TTAGGG repeats that are
displaced to form a single-stranded region, and the tail of the telomere is paired
with the homologous strand.
Shelterin - ans-A complex of six telomeric proteins in mammals that function to
protect telomeres from DNA damage repair pathways and to regulate telomere
length control by telomerase.
Telomerase - ans-The ribonucleoprotein enzyme that creates repeating units of
one strand at the telomere by adding individual bases to the II II DNA 3′ end, as
directed by an RNA sequence in the RNA component of the enzyme.
Nucleosome - ans-The basic structural subunit of chromatin, consisting of
approximately 200 bp of DNA and an octamer of histone
proteins.
Histones - ans-Conserved DNA-binding proteins that form the basic subunit of
chromatin in eukaryotes. H2A, H2B, H3, and H4 form an
octameric core around which DNA coils to form a nucleosome.
, Page |3
Linker histones are external to the nucleosome
Histone Tails - ans-Flexible amino- or carboxy-terminal regions of the core
histones that extend beyond the surface of the nucleosome; they are sites of
extensive posttranslational modification.
10-nm fiber - ans-A linear array of nucleosomes generated by unfolding from the
natural condition of chromatin.
Linker Histones - ans-A family of histones (such as histone H1) that are not
components of the nucleosome core; linker histones bind nucleosomes and/or
linker DNA and promote 30-nm fiber formation.
30-nm fiber - ans-A coil of nucleosomes. It is the basic level of organization of
nucleosomes in chromatin.
Nonhistones - ans-Any structural protein found in a chromosome except one of
the
histones
Micrococcal Nuclease (MNase) - ans-An endonuclease that cleaves DNA; in
chromatin, DNA is cleaved preferentially between nucleosomes.
Linker DNA - ans-Nonnucleosomal DNA present between nucleosomes.
, Page |4
Core DNA - ans-Region of nucleosomal DNA that has an invariant length of 146
bp, the minimum length of DNA needed to form a stable monomeric nucleosome,
and is relatively resistant to digestion by nucleases.
Histone Octamer - ans-The complex of two copies each of the four different core
histones (H2A, H2B, H3, and H4); DNA wraps around this complex to form the
nucleosome.
Core Histones - ans-One of the four types of histone (H2A, H2B, H3, and H4 and
their variants) found in the core particle derived from the nucleosome. (This
excludes linker histones.)
Histone Fold - ans-A motif found in all four core histones in which three α-helices
are connected by two loops.
Chromatosomes - ans-Nucleosomes that contain linker histones.
Histone Code - ans-The hypothesis that combinations of specific modifications on
specific histone residues act cooperatively to define chromatin
function.
Bromodomain - ans-A domain of 110 amino acids that binds to acetylated lysines
(often in histones).
Chromodomain - ans-Domains of approximately 60 amino acids that recognize
various methylated states of lysines in histones and other proteins; some have
other functions, such as RNA binding.
Lewin's Genes XII Adv. Molecular Bio Lewin's
Genes XII Composite 011
sRNA - ans-A small bacterial RNA that functions as a regulator of gene expression.
CRISPRs - ans-Clusters of regularly interspersed short palindromic repeats in
prokaryotes that are transcribed and processed into short RNAs that function in
RNA interference.
microRNA (miRNA) - ans-Small (21 to 23 nucleotides), evolutionarily conserved
noncoding RNAs that function in RNA silencing and posttranscriptional regulation
of gene expression. Bind to complementary sequences within the 3′ untranslated
region (UTR) of their target mRNAs and negatively regulate protein expression by
accelerating mRNA degradation and inhibiting mRNA translation.
RNA interference (RNAi) - ans-A process by which short 21- to 23-nucleotide
antisense RNAs, derived from longer double-stranded RNAs, can modulate
expression of mRNA by translation inhibition or degradation.
stRNA - ans-Short temporal RNA, a form of miRNA in eukaryotes that modulates
mRNA expression during development.
piRNA - ans-Piwi RNA, a special form of miRNA found in germ cells.
siRNA - ans-Short interfering RNA, an miRNA that prevents gene express
, Page |2
Kinetochore - ans-A small organelle associated with the surface of the centromere
that attaches a chromosome to the microtubules of the mitotic spindle. Each
mitotic chromosome contains two "sisters" that are positioned on opposite sides
of its centromere and face in opposite directions.
Telomere - ans-The natural end of a chromosome; the DNA sequence consists of a
simple repeating unit with a protruding single-stranded end.
T-loop - ans-Structure characterized by a series of TTAGGG repeats that are
displaced to form a single-stranded region, and the tail of the telomere is paired
with the homologous strand.
Shelterin - ans-A complex of six telomeric proteins in mammals that function to
protect telomeres from DNA damage repair pathways and to regulate telomere
length control by telomerase.
Telomerase - ans-The ribonucleoprotein enzyme that creates repeating units of
one strand at the telomere by adding individual bases to the II II DNA 3′ end, as
directed by an RNA sequence in the RNA component of the enzyme.
Nucleosome - ans-The basic structural subunit of chromatin, consisting of
approximately 200 bp of DNA and an octamer of histone
proteins.
Histones - ans-Conserved DNA-binding proteins that form the basic subunit of
chromatin in eukaryotes. H2A, H2B, H3, and H4 form an
octameric core around which DNA coils to form a nucleosome.
, Page |3
Linker histones are external to the nucleosome
Histone Tails - ans-Flexible amino- or carboxy-terminal regions of the core
histones that extend beyond the surface of the nucleosome; they are sites of
extensive posttranslational modification.
10-nm fiber - ans-A linear array of nucleosomes generated by unfolding from the
natural condition of chromatin.
Linker Histones - ans-A family of histones (such as histone H1) that are not
components of the nucleosome core; linker histones bind nucleosomes and/or
linker DNA and promote 30-nm fiber formation.
30-nm fiber - ans-A coil of nucleosomes. It is the basic level of organization of
nucleosomes in chromatin.
Nonhistones - ans-Any structural protein found in a chromosome except one of
the
histones
Micrococcal Nuclease (MNase) - ans-An endonuclease that cleaves DNA; in
chromatin, DNA is cleaved preferentially between nucleosomes.
Linker DNA - ans-Nonnucleosomal DNA present between nucleosomes.
, Page |4
Core DNA - ans-Region of nucleosomal DNA that has an invariant length of 146
bp, the minimum length of DNA needed to form a stable monomeric nucleosome,
and is relatively resistant to digestion by nucleases.
Histone Octamer - ans-The complex of two copies each of the four different core
histones (H2A, H2B, H3, and H4); DNA wraps around this complex to form the
nucleosome.
Core Histones - ans-One of the four types of histone (H2A, H2B, H3, and H4 and
their variants) found in the core particle derived from the nucleosome. (This
excludes linker histones.)
Histone Fold - ans-A motif found in all four core histones in which three α-helices
are connected by two loops.
Chromatosomes - ans-Nucleosomes that contain linker histones.
Histone Code - ans-The hypothesis that combinations of specific modifications on
specific histone residues act cooperatively to define chromatin
function.
Bromodomain - ans-A domain of 110 amino acids that binds to acetylated lysines
(often in histones).
Chromodomain - ans-Domains of approximately 60 amino acids that recognize
various methylated states of lysines in histones and other proteins; some have
other functions, such as RNA binding.
