Studied by 11 people
Class 12
Promoters
DNA sequences near the beginning of genes that signal RNA polymerase to begin TRANSCRIPTION
Terminators
sequences in RNA products that tell RNA polymerase to stop TRANSCRIPTION
Poly-A tail
3’ end mRNA consisting of 100-200 As
Exon
sequences found in both a genes DNA and the mature mRNA
expressed regions
Intron
sequences found in the DNA of a gene BUT NOT in the mature mRNA
intervening regions
5’ and 3’ Untranslated regions (UTRs)
5’ and 3’ ends in mRNAs that aren’t translated but are needed for the efficiency of TRANSLATION
located just after the methylated cap and just before he poly-A tail
transcribed from a gene’s exons
RNA splicing
the process that deletes intron and joins together successive exons to form mature mRNA
Alternate splicing
RNA splicing regulated so that at certain times or in certain tissues, some splicing signals may be ignored
produces different mRNA molecules that may encode related proteins with different (partially overlapping) amino acid sequences and functions
can basically allow a nucleotide sequence of a primary transcript to make more than one kind of polypeptide
Missense mutations (general infomation)
changing a codon into a mutant codon that specifies a different amino acid
conservative substitution = amino acid changed to another, but have similar properties
nonconservative substitution = amino acid changed into something with very different properties
effect on phenotype depends on how an amino acid substitution changes a protein’s structure and function
think about a change in the residual group (R group)
LOF example
Enhancers
located before promoters
are essentially a binding site for proteins that allow the proteins on promoters to stay for longer
makes mRNA TRANSCRIPTION last longer, meaning more proteins
Nonsense mutation
changes codon that specifies amino acid into one that doesn’t (stop codon)
result in the production of truncated proteins that lack all animo acids between the mutant codon and the C-terminus of the normal polypeptide
mutant polypeptide cannot function if it requires the missing amino acids for its activities
LOF example
Frameshift mutation
result from the insertion or deletion of nucleotides within the coding sequences
number of extra or missing nucleotide has to be divisible by three to NOT mess up the reading frame downstream of the mutation
usually result in truncated proteins (premature stop codons) with incorrect amino acids at the C-terminus
LOF example
Loss-of-function mutation (LOF)
any mutation that inside or outside a coding region that reduces or destroys protein activity
tend to be recessive
note: overall cannot predict if mutant allele will be dominant or recessive to wild-type
depends on how drastically a mutation influences protein production or activity and throughly phenotype depends on the wild-type level of protein
Null/amorphic mutation
a type of LOF mutation
LOF alleles that block the function of a protein completely
example: Mendel’s alleles that were recessive to the wild-type
Hypomorphic mutation
a type of LOF mutation
LOF allele that produces either less of the wild-type protein or a mutant protein that functions less efficiently
usually recessive to amorphic
Gain-of-function mutation (GOF)
rare mutations that either enhances a protein’s function, add new activity on a protein, or express a protein at the wrong time or place
almost always dominant to wild-type since a single allele can usually produce a protein that can alter phenotype, even in the presence of the normal protein (heterozygotes)
can be lethal when homozygous
pleiotropic, if there is absolutely no normal protein function, or if two doses of altered protein leads to inviability
note: overall cannot predict if mutant allele will be dominant or recessive to wild-type
depends on how drastically a mutation influences protein production or activity and throughly phenotype depends on the wild-type level of protein
Hypermorphic mutation
generates either more normal protein product than the wild-type or a more efficient mutant protein (a protein that does what it does better than normal)
Ex: FGFR3 gene, which inhibits bone growth, the most common form of dwarfism
GOF example
Neomorphic mutation
“new function”
creates a rare class of dominant GOF alleles that generate novel characteristics
some produce mutant proteins with a new function
some cause genes to produce normal protein, but at an inappropriate time or place (ectopic)
Ex: Huntington’s
Antimorphic/dominant-negative alleles
dominant mutant alleles of genes that encode proteins that not only fail to provide wild-type protein activity, but also prevent the normal protein from functioning
total activity in heterozygotes is far less than seen in wild-type homozygotes
Haploinsufficiency
LOF alleles dominant to normal alleles because normal alleles don’t produce enough product for wild-type phenotype
demonstrated in heterozygotes
