MMSC491 - EXAM 1 STUDY GUIDE
(CHAPTER 2) WITH CORRECT
ANSWERS 2026
1. structure of exons - ANSWER-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
2. function of exons - ANSWER-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
3. 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
4. structure of introns - ANSWER-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
5. function of introns - ANSWER-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.
6. define: transcriptional unit - ANSWER-the transcribed region of DNA
7. define: RNA splicing - ANSWER-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)
8. RNA splicing involves first cleaving the RNA transcript at the junction
between transcribed axons and introns
9. 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
10. RNA splicing is performed within the nucleus by spliceosomes,
complex assemblies of protein factors and small nuclear RNA (snRNA)
molecules
11. what is the role of RNA splicing in gene expression? - ANSWER-
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
, 12. define: splice donor site - ANSWER-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
13. define: splice acceptor site - ANSWER-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
14. describe the evolutionary value of RNA splicing - ANSWER-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
15. 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)
16. Summarize the process (i.e. the steps) of translation - ANSWER-
(1) The ribosome binds to mRNA at a specific area
17. (2) The ribosome starts matching tRNA anticodon sequences to
the mRNA codon sequence
(CHAPTER 2) WITH CORRECT
ANSWERS 2026
1. structure of exons - ANSWER-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
2. function of exons - ANSWER-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
3. 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
4. structure of introns - ANSWER-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
5. function of introns - ANSWER-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.
6. define: transcriptional unit - ANSWER-the transcribed region of DNA
7. define: RNA splicing - ANSWER-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)
8. RNA splicing involves first cleaving the RNA transcript at the junction
between transcribed axons and introns
9. 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
10. RNA splicing is performed within the nucleus by spliceosomes,
complex assemblies of protein factors and small nuclear RNA (snRNA)
molecules
11. what is the role of RNA splicing in gene expression? - ANSWER-
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
, 12. define: splice donor site - ANSWER-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
13. define: splice acceptor site - ANSWER-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
14. describe the evolutionary value of RNA splicing - ANSWER-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
15. 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)
16. Summarize the process (i.e. the steps) of translation - ANSWER-
(1) The ribosome binds to mRNA at a specific area
17. (2) The ribosome starts matching tRNA anticodon sequences to
the mRNA codon sequence
