Ch. 3 The Interrupted Gene (Exam 1) Flashcards
Define exon.
Sequence in DNA that codes for amino acid sequences
Define intron.
Sequence in DNA that does not translate into protein
How are interrupted genes expressed?
Via pre-mRNA
Why are interrupted genes longer than mature mRNA?
Introns are spread throughout interrupted genes
What is the basis of RNA splicing?
Removing introns and splicing the remaining exons together
What does alternative splicing produce?
Variant proteins from one gene in a eukaryotic cell
What regulates alternative splicing?
Introns
What regulates gene expression and DNA initiation?
Introns
Why is the correspondence between gene and polypeptide maintained after splicing?
The exon order does not change between DNA and RNA
What defines the length of a gene?
The pre-mRNA, which contains introns
How do mutations in exons directly affect polypeptides?
Exons code for polypeptides, and a change in the exon will lead to some sort of mutation
How do mutations in introns indirectly affect polypeptide production?
They affect mRNA production by halting exon splicing, which is typically deleterious
What is the most common outcome of an intron mutation?
A shortened polypeptide sequence
Define complementary DNA (cDNA).
DNA corresponding to the OG sequence, with the restriction sites on exons included
Why is it that exon similarity is conserved but intron similarity isn’t?
Introns are not bound by any selective pressure to produce useful polypeptide sequences
Exons and introns mutate at the same rate, but exons…
Are selectively eliminated more often
Where is intron position conserved?
Homologous genes compared across different organisms
Overall gene length is determined by…
Introns
What do alternate initiation & termination codons allow?
Multiple variants of a polypeptide chain
What happens when mRNA is read from different reading frames?
Different polypeptide sequences are produced from the same DNA sequence
Having 2 alternate start codons in a single sequences can produce…
A short or full-length polypeptide
Under what condition can a sequence successfully translate a polypeptide?
As long as the gene section being translated is functional
Define overlapping gene (HINT: include reading frame).
A gene that uses more than one reading frame, which means that part of a nucleotide sequence overlaps with another
Overlapping genes encode 2 { } proteins.
Nonhomologous
What splicing mechanism creates homologous proteins?
Alternative splicing
How do homologous proteins differ?
By presence or absence of certain regions
What two ways does alternative splicing do its job?
1) Including/excluding individual exons
2) Choosing between alternate exons
The gene sequence that makes a specific protein is based on how many potential reading frames?
3
How does alternate splicing affect protein?
The translated amino acid sequence and overall function will differ
How does alternative splicing benefit eukaryotes?
Increasing protein biodiversity
What type of mutations do introns accumulate over time?
Point substitutions
Define protein domain.
Distinct functional and/or structural unit of protein
How are exons associated with protein domains?
Because they encode polypeptide sequences with certain functions
The exons of some genes appearing to be homologous to the exons of others is indicative of…
Common ancestry of the functional domain
What does a common feature in a set of genes identify?
Some shared property proceeding their evolutionary separation
Define gene family.
Gene group encoding related or identical products resulting from gene duplication events (e.g. globin genes having similar organization)
The exon structure of globin genes corresponds to…
Protein function
