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