Genetics Exam 2 Vocab
chromatin
DNA and histones in eukaryotes
regulatory sequence
DNA sequence that can repress or promote the transcription of a gene
structural gene
DNA sequence that codes for a protein that will act in the metabolism of the cell
regulatory gene
DNA sequence that codes for a protein which function is to induce or prevent gene expression of other genes
acetylation
addition of acetyl groups to histones. it promotes gene expression
methylation
addition of methyl groups to histones or nucleotides. it represses gene expression when added to nucleotides. it either promotes or represses gene expression when added to histones
peptide bond
chemical link between two amino acids
correpressor
cofactor that binds to a repressor and activates it so the repressor can bind to the operator and prevent gene expression
inducer
cofactor that binds to the repressor and inactivates it so the repressor unbinds from the operator
TATA box
consensus sequence in the promoters of eukaryotes
gene regulation
control of the expression of genes
CpG islands
dinucleotides of Cytosines and Guanines where heavy methylation can occur
RNA polymerase
enzyme that uses a DNA template to copy a strand of RNA
reading frame
forms in which an mRNA molecule can be decoded by the ribosome
operon
group of prokaryotic genes that have one promoter and are expressed at the same time
basal transcription apparatus
group of the minimum transcription factors plus the RNA polymerase that are necessary to start transcription
5'cap
guanine added ti the mature mRNA
upstream
in the template strand, direction towards the promoter
downstream
in the template strand, the direction towards the terminator
euchromatin
loose arrange of DNA around histones. transcription can happen in this conformation
ribosome
machine composed of rRNA and proteins that carries out translation
RNA
molecule made up of (usually a single) strand of nucelotides (A, C, U, G)
DNA
molecule made up of a double strand of nucleotides (A,C,T,G)
cofactor
molecule that binds to an allosteric protein and alters its conformation/function
spliceosome
molecule that identifies consensus regions in introns and exons and removes the corresponding segments
amino acid
monomer of peptides and proteins
nucleotide
monomer that makes up nucleic acids. it is made of a nitrogenated base, a pentose and a phosphate group
repressible operon
operon that is on but can be turned off in the presence of a cofactor
inducible operon
operon that is turned off but can be turned on by the presence of a cofactor
peptidyl site
part of the ribosome where the first codon binds and where the peptide bonds between amino acids is carried out
aminoacyl site
part of the ribosome where the second and subsequent tRNAs arrive
exit site
part of the ribosome where the tRNA free of amino acid is removed
big ribosomal unit
part of the ribosome with higher weight, it is the part that catalyzes the peptide bond
small ribosomal unit
part of the ribosome with lower weight, it Is the part that decodes the triplets of nucleotides
allosteric protein
polypeptide with two binding sites. a primary one that binds to the main substrate and a secondary where a cofactor can bind and alter the function of the polypeptide
alternative splicing
process by which one gene can produce more than one transcript/protein
transcription factor
protein that can promote or repress the transcription of a gene
repressor
protein that prevents gene expression
negative control
repression of gene expression
promoter
section of a gene where the RNA polymerase binds. it is not transcribed
PolyA tail
section of a mature mRNA that is added in the 3' side and protects the molecule from degradation
promoter
section of a transcription unit that is required for the RNA polymerase to bind but is not transcribed
operator
segment of DNA that overlaps with promoter and coding sequence of a prokaryotic gene. This is where the repressor binds
insulator
segment of DNA that prevents an enhancer from promoting expression of a gene
enhancer
segment of DNA that promotes gene expression and is located far from the promoters it activates
terminator
segment of a gene that indicates the RNA polymerase to stop copying. it is transcribed
coding region
segment of a gene that is to be transcribed
core promoter
segment of a gene where the basal transcription apparatus binds
untranslated region (UTR)
segment of a transcript that is located before the start codon or after the stop codon and thus it is not translated
intron
segment of a transcript that is removed from the mature mRNA molecules
exon
segment of eukaryotic transcript that remains after the mRNA matures
consensus sequence
sequence that puts together the conserved nucleotides across many taxa
3' side
side of a nucleic acid that has an unbinded (free) pentose
5' side
side of a nucleic acid that has an unbinded (free) phosphate group
wobble theory
statement that explains how the structure of mRNA and tRNA prevents a perfect match, allowing the third position in the codons to be more flexible in the way it binds to different nucleotides. it helps in part to explain that the genetic code is degenerate
coding strand
strand of DNA that is not transcribed, but has the code of the RNA molecule that will be produced (except that Ts are exchanged by Us)
template strand
strand of DNA that is used by the RNA polymerase to produce the RNA molecule
isoaccepting tRNA
tRNAs with different anticodons but that carry the same amino acid
heterochromatin
tight arrange of DNA around histones. transcription cannot occur in this conformation
mediator
transcription factor that helps enhancers and promoters interact
genetic code
translation of all possible codons into amino-acids, start or stop signals
anticodon
triplet of nucleotides in tRNA that bind to the mRNA during the translation process
codon
triplet of nucleotides in the messenger RNA that codes for an amino acid or a stop message in the translation process
synonymous codon
triplet of nucleotides that code for the same amino acid in a mRNA sequence
start codon
triplets of nucleotides that signals the ribosome to begin translation (AUG)
stop codon
triplets of nucleotides that signals the ribosome to refrain from translating any more nucleotides
rRNA
type of RNA that forms part of ribosomes
tRNA
type of RNA that has the anticodon for each amino acid
mRNA
type of RNA that has the codons that will go in the ribosome to be the template for a protein
RNA interference
type of RNA that represses gene expression at different levels
positive control
when gene expression is promoted
attenuation
when transcription starts but finishes early due to the presence or absence of a factor. it reduces gene expression