Chapter 11 Flashcards
transcription factors
regulatory proteins that control whether or not a gene is active
repressor
binds to a specific site to prevent transcription
activator
stimulates transcription
how do prokaryotes conserve energy and resources
make certain proteins only when they are needed
beta-galactoside permease
carrier protein in the bacterial cell membrane that moves the sugar into the cell
beta-galactosidase
an enzyme that hydrolyses actose to glucose and galaactose
beta-galactoside transacetylase
transfers acetyl groups from acetyl CoA to certain beta-galactosides
inducers
stimulate the transcription of specific genes
inducible genes
genes that can be activated by inducers
constitutive genes
genes expressed most of the time at a constant rate
operon
a cluster of genes with a single promoter
operator
repressor-binding site that can bind very tightly wiht a repressor protein
inducible operon
turned off unless needed
repressible operon
turned on unless needed
regulatory gene
any gene that encodes a regulatory protein (a transcription factor)
structural gene
any gene that encodes a protein not directly involved in gene regulation
corepressor
a molecule that binds to the repressor, causing it to change shape and bind to the operator, thereby inhibiting transcription
what type of pathways do inducible systems generally control?
catabolic pathways
what type of pathways do repressible systems generally control?
anabolic pathways
sigma factors
proteins in prokaryotes that can bind to RNA polymerase and direct the polymerase to specific promoters
virus
injects genetic material into a host cell
lytic
viral genome takes over host cell, host cell begins to produces new viral particles, cell breaks open and releases these virions
lysogenic
dormant phase, where viral genome is incorporated into the host cell genome
what happens in the early stage of the lytic cycle?
viral genes near the promoter are transcribed, and encode proteins that shut down expression of host genes
what happens in the late stage of the lytic cycle?
viral late genes are transcribed to encode enzymes that will lyse the host cell and release the new virions
constitutive genes
expressed most of the time
inducible genes
expressed only when needed
TATA box
a core promoter that is rich in A-T base pairs
general transcription factors
bind to most promoters and allow RNA polymerase II to transcribe the protein-coding genes
how is transcription initiated?
by a combination of factors
NFATs
nuclear factors of activated T cells that control the expression of genes essential for the immune response
how are DNA-protein interactions determined?
base sequence of a binding site on DNA
what are the two ways for prokaryotes to coordinate the regulation of several genes?
arranging them in an operon, or using sigma factors
how can the expression of genes be coordinated?
if they share regulatory sequences that bind the same transcription factors
what are some life cycle strategies of viruses?
efficient, faster life cycles than the host cell and can thus release more new virions
HIV
infective agent that causes AIDS in humans
reverse transcriptase
makes a DNA strand complementary to the RNA, and degrades the RNA
provirus
integrated viral DNA
Tat
protein that binds to the 5’ end of viral RNA, increasing the production of full length viral RNA
epigenetic changes
alterations in either DNA or chromosomal proteins that can then be passed on to daughter cells after mitosis or meiosis
chromatin remodeling
alteration of chromatin structure
histone proteins
positively charged proteins around which DNA is wound
histone acetyltransferases
add acetyl groups to positively charged amino acids and neutralise them
histone deacetylases
remove the acetyl groups from histones and repress transcription
histone methylation
can contribute to activation or repression of gene expression
DNA methyltransferase
catalyses the covalent addition of a methyl group to the cytosines in DNA
CpG islands
transcriptionally active promoters containing regions of DNA rich in CpG
maintenance methyltransferase
catalyses the formation of 5-methylcytosine in the new DNA strands
demethylase
enzyme that catalyses the removal of the methyl group
euchromatin
contains the DNA that is transcribed into mRNA
heterochromatin
contains genes that are generally not transcribed
what is an important factor in epigenetic modifications?
environment
genomic imprinting
offspring would inherit a maternal gene that is transcriptionally inactive and a paternal gene that is transcriptionally active
alternative splicing
generates a family of different proteins with different activities and functions from a single gene
miRNA
noncoding regions are transcribed into these tiny RNA molecules, can silence genes
how an the translation of mRNA be regulated?
inhibition of translation with miRNAs, modification of the 5’ cap, translational repressor proteins
ubiquitin
76-amino acid protein that gets attached to a lysine residue
proteasome
a huge protein complex
how are cyclins broken down at just the right time
by proteasomes
