Cellular control Flashcards
what is transcriptional level control
when gene expression is controlled by altering the rate of transcription of genes
what are transcription factors
proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription
what are factors called that start transcription
activators
what are factors called that stop transcription
repressors
in prokaryotes control of gene expression often involves transcription factors binding to what
operons
what is an operon
a section of DNA that contains a cluster of structural genes that are all transcribed together as well as control elements and sometimes a regulatory gene
what do structural genes do
code for useful proteins such as enzymes
what do the controls meets contain
promoters (a DNA sequence located before the structural genes that RNA polymerase binds to and an operator (a DNA sequence that transcription factors bind to
what does the regulatory gene do
codes for an activator or repressor
how does the lac operon function when lactose is not present
regulatory gene produces lac repressor
this then binds to the operator site where no lactose is present
this blocks transcription as RNA polymerase can’t bind to the promoter
how does the lac operon function when lactose is present
lactose binds to the reposer, changing its shape so it can no longer bind to the operator site
RNA polymerase can then begin transcription in structural genes
what is the lac operon, where is it found and what does it do
where the genes are found that produce enzymes needed to respire lactose
found in E coli
what is post-transcriptional level control
when control of gene expression takes place after post-transcriptional level and mRNA is edited
what are the sections of DNA called that don’t code for amino acids
introns
what are the sections of DNA called that do code for amino acids
exons
what are mRNA strands called that contain introns and exons
primary mRNA transcripts
what happens during ‘splicing’ and where does it take place
introns are removed from the primary mRNA and exons are joined together to form mature mRNA
nucleus
some proteins have to be activated after they are made what is an example of this
cAMP (post-transcriptional level control)
what is the name for genes that control body plan development
Hox genes
what are homeobox sequences
regions on how genes which are highly conserved so have changed very little during the evolution of different organisms that possess them
mutations can be either
beneficial or harmful
what is substitution
one or more bases are swapped for another base
what is deletion
one or more bases are removed
what is insertion
one or more bass are added
what is a frameshift mutation
when insertion or deletion changes the way the rest of the base sequences is read
why may a mutation have a neutral effect on an organism
a base is changed in the triplet but the amino acid it codes for doesn’t change
the new triplet code codes for a different protein but it is chemical similar to the function of the original one
the mutated triplet code codes for something not involved in protein function
what is continuous variation
when individuals of a population vary within a range, no distinct categories
what is discontinuous variation
when individuals vary within distinct categories
how does variation in the phenotype occur
same genes but different alleles
crossing over and independent assortment
differences in environment
what is a polygenic characteristic
characteristic influenced by many genes, shows continuous variation
what is a monogenic characteristic
characteristics influenced by one gene, shows discontinuous variation
what is an allele
different versions of the same gene
what is a gene
a sequence of bases on a DNA molecule that codes for a protein
what is genotype
the alleles an organism has
what is a phenotype
the characteristics produced by an organisms alleles
what does homozygous mean
when an organism contains two copies of the same allele
what does heterozygous mean
if an organism contains two different alleles
what are codominant alleles
alleles that are both expressed in the phenotype cause neither one is recessive
what is a carrier
a person carrying an allele which is not expressed in phenotype but can be passed on to offspring
what phenotypic ratio would you expect for a monogenic genetic diagram
3:1
what are dihybrid crosses used for
used to show the likelihood of offspring inheriting certain combinations of the two characteristics from particular parents
what ratio do you expect from a dihybrid cross
9:3:3:1
what does it mean if a characteristic is sex linked
the alleles that code for that characteristic are found on the sex chromosome
what is epistasis
when the allele of one gene masks the expression of the alleles of other genes
what is an autosome
a chromosome that is not a sex chromosome
what ratio would you expect for a dominant epistatic allele cross diagram
12:3:1
