MMSC 491 - EXAM 1 (CHAPTER 2) VERIFIED STUDY
GUIDE
structure of exons - Answers - exons are made up of stretches of DNA that will
ultimately be translated into amino acids and proteins. In the DNA of eukaryotic
organisms, exons can be together in a continuous gene or separated by introns in a
discontinuous gene. When the gene is transcribed into pre-mRNA the transcript
contains both introns and exons
function of exons - Answers - Exons are pieces of coding DNA that encode proteins.
Different exons code for different domains of a protein. The domains may be encoded
by a single exon or multiple exons spliced together. The presence of exons and introns
allows for greater molecular evolution through the process of exon shuffling. Exon
shuffling occurs when exons on sister chromosomes are exchanged during
recombination. This allows for the formation of new genes
Exons also allow for multiple proteins to be translated from the same gene through
alternative splicing. This process allows the exons to be arranged in different
combinations when the introns are removed
structure of introns - Answers - In general, introns are much longer than exons; they can
make up as much as 90% of a gene and can be over 10,000 nucleotides long
function of introns - Answers - While introns were initially - and to an extent still are -
considered "junk DNA", it has been shown that introns likely play an important role in
regulation and gene expression. As introns cause an increase in gene length, this
increases the likelihood of crossing over and recombination between sister
chromosomes. This increases genetic variation and can result in new gene variants
through duplications, deletions, and exon shuffling. Introns also allow for alternative
splicing. This allows a single gene to encode multiple proteins as the exons can be
assembled in multiple ways.
define: transcriptional unit - Answers - the transcribed region of DNA
define: RNA splicing - Answers - the process whereby some precursor RNA transcripts
are cleaved into sequences, some of which (exons) are retained and fused (spliced) to
give the mature RNA whereas others are discarded (intons)
RNA splicing involves first cleaving the RNA transcript at the junction between
transcribed axons and introns
, The individual transcribed intron sequences do not seem to have any useful function
and our degraded, but the transcribed exon sequences are then covalently linked
(spliced) intern to make maturity
RNA splicing is performed within the nucleus by spliceosomes, complex assemblies of
protein factors and small nuclear RNA (snRNA) molecules
what is the role of RNA splicing in gene expression? - Answers - RNA splicing is a
process in eukaryotic gene expression where that genetic information is altered while in
RNA form. In splicing, specific regions of the RNA transcript are cut out and the flanking
sequences are pasted together. Regulation of splicing therefore represents a critical
step of gene expression
define: splice donor site - Answers - the site that defines the junction between the end of
an exon in RNA and the start of the following intron. The junction sequence often
conforms to the consensus sequence (C/A) AGguragu, where r in the purine and capital
letters denote the end nucleotides of the exon
define: splice acceptor site - Answers - the site that defines the junction between the
end of an intron in RNA and the start of the following exon. The junction sequence often
conforms to the consensus sequence yyyyyyyyyyynyagR, where y is the pyrimidine, n is
any nucleotide, and R is a purine that is the first nucleotide of the exon
describe the evolutionary value of RNA splicing - Answers - Why do we need to split the
genetic information and genes into sometimes so many different little exons? - To
stimulate the formation of novel genes and novel gene products that can permit greater
functional complexity during evolution
The huge complexity of humans and other multicellular organisms has been driven by
genome evolution. In addition to periodic gene duplication, various genetic mechanisms
allow individual exons to be duplicated or swapped from one gene to another on an
evolution every time scale. That allows different ways of combining exons to produce
novel hybrid jeans. An additional source of complexity comes from using different
combinations of exons to make alternative transcripts from the same gene (alternative
splicing)
Summarize the process (i.e. the steps) of translation - Answers - (1) The ribosome
binds to mRNA at a specific area
(2) The ribosome starts matching tRNA anticodon sequences to the mRNA codon
sequence
(3) Each time a new tRNA comes into the ribosome, the amino acids that it was carrying
gets added to the elongating polypeptide chain
GUIDE
structure of exons - Answers - exons are made up of stretches of DNA that will
ultimately be translated into amino acids and proteins. In the DNA of eukaryotic
organisms, exons can be together in a continuous gene or separated by introns in a
discontinuous gene. When the gene is transcribed into pre-mRNA the transcript
contains both introns and exons
function of exons - Answers - Exons are pieces of coding DNA that encode proteins.
Different exons code for different domains of a protein. The domains may be encoded
by a single exon or multiple exons spliced together. The presence of exons and introns
allows for greater molecular evolution through the process of exon shuffling. Exon
shuffling occurs when exons on sister chromosomes are exchanged during
recombination. This allows for the formation of new genes
Exons also allow for multiple proteins to be translated from the same gene through
alternative splicing. This process allows the exons to be arranged in different
combinations when the introns are removed
structure of introns - Answers - In general, introns are much longer than exons; they can
make up as much as 90% of a gene and can be over 10,000 nucleotides long
function of introns - Answers - While introns were initially - and to an extent still are -
considered "junk DNA", it has been shown that introns likely play an important role in
regulation and gene expression. As introns cause an increase in gene length, this
increases the likelihood of crossing over and recombination between sister
chromosomes. This increases genetic variation and can result in new gene variants
through duplications, deletions, and exon shuffling. Introns also allow for alternative
splicing. This allows a single gene to encode multiple proteins as the exons can be
assembled in multiple ways.
define: transcriptional unit - Answers - the transcribed region of DNA
define: RNA splicing - Answers - the process whereby some precursor RNA transcripts
are cleaved into sequences, some of which (exons) are retained and fused (spliced) to
give the mature RNA whereas others are discarded (intons)
RNA splicing involves first cleaving the RNA transcript at the junction between
transcribed axons and introns
, The individual transcribed intron sequences do not seem to have any useful function
and our degraded, but the transcribed exon sequences are then covalently linked
(spliced) intern to make maturity
RNA splicing is performed within the nucleus by spliceosomes, complex assemblies of
protein factors and small nuclear RNA (snRNA) molecules
what is the role of RNA splicing in gene expression? - Answers - RNA splicing is a
process in eukaryotic gene expression where that genetic information is altered while in
RNA form. In splicing, specific regions of the RNA transcript are cut out and the flanking
sequences are pasted together. Regulation of splicing therefore represents a critical
step of gene expression
define: splice donor site - Answers - the site that defines the junction between the end of
an exon in RNA and the start of the following intron. The junction sequence often
conforms to the consensus sequence (C/A) AGguragu, where r in the purine and capital
letters denote the end nucleotides of the exon
define: splice acceptor site - Answers - the site that defines the junction between the
end of an intron in RNA and the start of the following exon. The junction sequence often
conforms to the consensus sequence yyyyyyyyyyynyagR, where y is the pyrimidine, n is
any nucleotide, and R is a purine that is the first nucleotide of the exon
describe the evolutionary value of RNA splicing - Answers - Why do we need to split the
genetic information and genes into sometimes so many different little exons? - To
stimulate the formation of novel genes and novel gene products that can permit greater
functional complexity during evolution
The huge complexity of humans and other multicellular organisms has been driven by
genome evolution. In addition to periodic gene duplication, various genetic mechanisms
allow individual exons to be duplicated or swapped from one gene to another on an
evolution every time scale. That allows different ways of combining exons to produce
novel hybrid jeans. An additional source of complexity comes from using different
combinations of exons to make alternative transcripts from the same gene (alternative
splicing)
Summarize the process (i.e. the steps) of translation - Answers - (1) The ribosome
binds to mRNA at a specific area
(2) The ribosome starts matching tRNA anticodon sequences to the mRNA codon
sequence
(3) Each time a new tRNA comes into the ribosome, the amino acids that it was carrying
gets added to the elongating polypeptide chain
