Gene Expression Unit Test

gene expression

DNA directs the synthesis of proteins

transcription

synthesis of RNA using info in the DNA, happens in nucleus

translation

synthesis of a polypeptide using info in mRNA, happens in ribosomes

protein building in prokaryotes

dont have nuclei, nuclear membranes dont separate DNA and mRNA from ribosomes

protein building in eukaryotes

have nuclei, nuclear envelope separates transcription from translation

start codon

AUG or Met

DNA transcribing enzyme

RNA polymerase

template DNA strand

noncoding strand

initiation

RNA polymerase binds to promoter, DNA unwinds, polymerase initiates RNA synthesis at start point

elongation

polymerase unwinds DNA and elongates RNA transcript 5’ → 3’, DNA strands re-form double helix

termination

RNA transcripts released, polymerase detaches from DNA

promoter

binds to polymerase and initiates transcription

terminator

sequence that signals end of transcription

5’ cap and poly A tail advantages

facilitate export of mRNA from nucleus, protect mRNA from degradation by hydrolytic enzymes

introns

noncoding segments of nucleic acid that lie between coding regions

exons

sequences of RNA that exit the nucleus

ribozyme

RNA molecules that function as enzymes

rRNA

makes up ribosomes together with proteins

mRNA

carries genetic material from DNA to protein synthesizing machinery of cell

tRNA

transfers amino acids from cytoplasmic pool of amino acids to growing polypeptides in a ribosome

anticodon

base pairs with specific mRNA codon

ribosomes role in translation

contain RNA, assemble proteins

P site

holds tRNA carrying growing polypeptide chain

A site

holds tRNA carrying next amino acid to be added to the chain

E site

discharged tRNAs leave through it

mutation

change in nucleotide sequence of an organisms DNA or in the DNA or RNA of a virus

point mutation

changes in a single nucleotide pair of a gene

frameshift mutation

nucleotides are inserted/deleted from gene and number isnt a multiple of 3, resulting in improper grouping of nucleotides into codons

missense mutation

nucleotide pair substitution, results in a codon that codes for different amino acid

nonsense mutation

changes an amino acid codon to one of the three stop codons, resulting in shorter and non-functional protein

insertion or deletion mutation

adding or deleting one or more nucleotide pairs to/from a gene

silent mutation

nucleotide-pair substitution that has no observable effect on the phenotype

mutagens mutation

chemical/physical agent that interacts with DNA and can cause a mutation

nontemplate DNA strand

coding strand

codon

three based sequence found on mRNA

poly A tail

100-200 adenine nucleotides, increases stability, helps with exporting from nucleus

5’ GTP cap

modified guanine nucleotide, protects transcript, helps ribosome attach to mRNA

alternative splicing

process of splicing introns and connecting retained exons in mature mRNA transcript

retroviruses

introduce viral RNA, not DNA, into host cells

reverse transcriptase

copies viral RNA into viral DNA

abnormalities in gene expression

can lead to imbalances and diseases

operator

on/off switch that can control the whole group of genes, controls access of RNA polymerase to promoter

operon

promoter, operator, and genes they control

histone acetylation

acetyl groups are attached to positively charged lysines in histone tails, loosens chromatin structure, promotes initiation of transcription

DNA methylation

addition of methyl groups to certain bases in DNA, condenses chromatin and reduces transcription

epigenetic inheritance

inheritance of traits transmitted by mechanisms not directly involving nucleotide sequence

activator

transcription factor (protein) that binds to a switch and stimulates transcription of a gene

regulatory sequences

stretches of DNA that can be used to promote synthesis

regulatory proteins

used to assist with promotion/inhibition of protein synthesis

epigenetic changes

reversible modifications of DNA or histones

histones

proteins used to wrap DNA around

tissues

groups of cells that have same function

cell differentiation

cells in the same organism having different phenotypes

sequential gene expression

results in development from undifferentiated cell to differentiated

operons

closely linked genes that produce a single mRNA molecule during transcription

regulatory genes

can control expression of all genes at same time

inducers

molecules that can bind to regulatory protein and cause it to change shape

promoter

DNA sequences where RNA polymerase and transcription factors bind to initiate transcription

triploidy

having three copies of a particular chromosome

polyploidy

having multiple sets of homologous chromosomes

naked DNA

DNA not protected by proteins or other molecules

transduction

transmission of foreign DNA into a cell when a viral genome integrates with host genome

conjugation

cell-to-cell transfer of DNA

transposition

movement of DNA segments in and between DNA molecules

repressor protein

binds to operator and blocks RNA polymerase from attaching to promoter, prevents transcription

inducible operons

stimulated when molecule interacts with regulatory proteins

repressible operons

activated by a corepressor and can then bind to operator and block transcription

determination

point where an embryonic cell is irreversibly committed to becoming a particular cell type

stem cells

unspecialized cells that can reproduce themselves and differentiate into different tissues

induced pluripotent stem cells

can be returned to their undifferentiated state and then turn into any cell