Genetics Exam test quiz and
answers graded A+
DSCAM - ANS✅✅-regulates neuron adhesion
-has 19,008 alternatively spliced forms which provide a signature for each neuron, and allow
neurons to correctly "wire up" the central nervous system
transcription and RNA processing - ANS✅✅are coupled processes
A. transcription initiation and elongation-in the exon, capping machinery is recruited early, when
length of pre-mRNA is only 20-40 nucleotides
-splicing machinery is recruited to each intron as the intron is being transcribed
B. termination-introns are not necessarily spliced in the same order in which they are transcribed
-splicing recruits proteins to the exon junction that function later to facilitate export of the mRNA
-polyadenylation machinery is recruited when transcription is terminated
C. release and export-a 5' cap is in place
-all introns are removed prior to the release of the mRNA from the transcription complex. The exon
junctions are marked with export proteins as well as proteins used in the first round of translation to
detect premature chain-termination codons
-a poly A tail has been added to the 3' end
coupled processes - ANS✅✅occurrence of one event initiates the next event
"splicing as they go"
characteristics of human genes - ANS✅✅median= 122 bp
number of exons= 7
number of aa= 367
major concepts- transcription and RNA processing - ANS✅✅-RNA similar chemically to DNA, but
composed of A,C,G, and U (instead of T), and contains ribose (not deoxyribose) sugars
-transcription proceeds 5' to 3' and produces an RNA transcript
-genes include 5' regulatory regions (including the promoter), the coding region, and 3' regulatory
regions
,-in eukaryotes, the primary transcript is modified with a 5' cap, a 3' poly A tail, and is spliced to
remove introns
-transcription and RNA processing are coordinate processes involving molecular machinery
consisting of protein and RNA molecules
splicing - ANS✅✅-the 2' OH group of an adenine (a) formed a bond with the phosphate group at
the 5' splice site, creating a loop in the RNA molecule
-the released free 3' OH end of the exon sequence then reacts with the start of the next exon
sequence, joining the 2 exons together
-the intron larait is release. The exons are joined together.
-splicing is usually controlled by a complex of proteins and RNAs called the spliceosome
-not mixing and matching splicing
-RNAS pairing with each other changes their activity
snRNPs - ANS✅✅-control the specificity of splicing (small nuclear ribonucleoprotein particles)
-U1 RNA binds to 5' and 3' ends of intron
-U2 RNA interacts with paired U4/U6
-U2 pairs with U6 and intron
-U5 comes in and facilitates splicing
self-splicing introns - ANS✅✅-self splicing introns fold into structures that bring the 2 nucleotides
that engage in the splicing reaction into proximity
-RNAs that fold up and have enzymatic activity on their own (catalyze reactions) are called ribozymes
ex. of ribozymes - ANS✅✅self splicing introns
primary transcipts of many genes are alternatively spliced to yield different products - ANS✅✅-the
same RNA transcript can be processed differently in different cell types, or in different conditions
-different proteins can be produced from the same gene transcipt by inclusion or exclusion of
specific exons
-alternative splicing is very common. Ca. 30,000 human gene may encode 64,000-90,000 different
proteins
-can produce multiple transcripts with different functions (alternative splicing)
,insulin receptor is alternatively spliced - ANS✅✅-in RNA processing in the liver, the exons 9-13 are
all included in the messenger RNA and the resulting protein has low affinity for insulin
-this form of the insulin receptor is expressed in tissues that are normally exposed to high levels of
insulin. It is not as sensitive as insulin.
-muscle- missing exon 11
-in RNA processing in skeletal muscle, the codons in exon 11 are excluded from the messenger RNA
and the resulting protein has high affinity for insulin
-this form of the insulin receptor is expressed in tissues that are normally exposed to LOW levels of
insulin. It is more sensitive to insulin (change function of receptor)
genes transcribed from both DNA strands as templates - ANS✅✅-direction of transcription is
determined by the promoter at the beginning of each gene
-genes transcribed from left to right use the bottom DNA strand as the template; those transcribed
from right to left use the top strand as the template
the transcribed RNA molecule - ANS✅✅-has a 5' untranslated region (5' UTR)
-open reading frame specifies the polypeptide chain
-3- untranslated region= 3' UTR
-in prokaryotes, the primary transcript= the messenger RNA (mRNA) (finished product in
prokaryotes)
-in eukaryotes, the primary transcript undergoes further modifications (RNA processing) before it
becomes mRNA
eukaryotic gene structure - ANS✅✅transcription: 5' end-> promoter (transcription start site)->
exons and introns-> stop codon -> termination region -> 3' end
then transcription: 5' exons and introns- 3' UTR
then RNA processing (mRNA transcript)
5'cap-> coding sequence-> stop-> 3' poly A tail (exons and introns get spliced)
RNA processing- 5' cap - ANS✅✅5- cap-> coding sequence-> stop
-5' RNA capped using a modified guanosine linked 5'-5'
-the 5' cap is necessary for the ribosome to bind the mRNA and begin protein synthesis
, -5' cap= modified methylated guanosine
-protects RNA end from degradation
RNA processing- poly A tail - ANS✅✅5' cap-> coding sequence- stop->poly a tail-> 3' OH
-3' end modified by the addition of a sequence called the poly A tail
-poly A tail can be up to 200 A residues long, and is thought to regulate RNA stability
-protects 5' end of RNA
-structure of RNa determines how ling it is
-poly A tail used to extract mRNA by adding poly A
RNA processing-splicing - ANS✅✅-exons and introns-> RNA processing
-mRNA transcript- coding sequence- stop-> poly A trail -> 3' OH
introns - ANS✅✅intervening sequences that are removed by RNA splicing (remember introns
interrupt)
exons - ANS✅✅the coding segments of the gene. Exons are joined to form the coding sequence.
(Exons are expressed)
introns - ANS✅✅interrupt
exons - ANS✅✅expressed
chain initiation and elongation - ANS✅✅-does not start with AUG because not translation
chain termination - ANS✅✅-inverted repeats are characteristic of many termination sites
-RNA polymerase makes RNA
-GC rich because 3H bonds=more stable bonding structure
-the inverted repeats can undergo base pairing and enable the RNA transcript to form a hairpin
structure
transcription does not have to - ANS✅✅be complete before a new transcript is initiated
answers graded A+
DSCAM - ANS✅✅-regulates neuron adhesion
-has 19,008 alternatively spliced forms which provide a signature for each neuron, and allow
neurons to correctly "wire up" the central nervous system
transcription and RNA processing - ANS✅✅are coupled processes
A. transcription initiation and elongation-in the exon, capping machinery is recruited early, when
length of pre-mRNA is only 20-40 nucleotides
-splicing machinery is recruited to each intron as the intron is being transcribed
B. termination-introns are not necessarily spliced in the same order in which they are transcribed
-splicing recruits proteins to the exon junction that function later to facilitate export of the mRNA
-polyadenylation machinery is recruited when transcription is terminated
C. release and export-a 5' cap is in place
-all introns are removed prior to the release of the mRNA from the transcription complex. The exon
junctions are marked with export proteins as well as proteins used in the first round of translation to
detect premature chain-termination codons
-a poly A tail has been added to the 3' end
coupled processes - ANS✅✅occurrence of one event initiates the next event
"splicing as they go"
characteristics of human genes - ANS✅✅median= 122 bp
number of exons= 7
number of aa= 367
major concepts- transcription and RNA processing - ANS✅✅-RNA similar chemically to DNA, but
composed of A,C,G, and U (instead of T), and contains ribose (not deoxyribose) sugars
-transcription proceeds 5' to 3' and produces an RNA transcript
-genes include 5' regulatory regions (including the promoter), the coding region, and 3' regulatory
regions
,-in eukaryotes, the primary transcript is modified with a 5' cap, a 3' poly A tail, and is spliced to
remove introns
-transcription and RNA processing are coordinate processes involving molecular machinery
consisting of protein and RNA molecules
splicing - ANS✅✅-the 2' OH group of an adenine (a) formed a bond with the phosphate group at
the 5' splice site, creating a loop in the RNA molecule
-the released free 3' OH end of the exon sequence then reacts with the start of the next exon
sequence, joining the 2 exons together
-the intron larait is release. The exons are joined together.
-splicing is usually controlled by a complex of proteins and RNAs called the spliceosome
-not mixing and matching splicing
-RNAS pairing with each other changes their activity
snRNPs - ANS✅✅-control the specificity of splicing (small nuclear ribonucleoprotein particles)
-U1 RNA binds to 5' and 3' ends of intron
-U2 RNA interacts with paired U4/U6
-U2 pairs with U6 and intron
-U5 comes in and facilitates splicing
self-splicing introns - ANS✅✅-self splicing introns fold into structures that bring the 2 nucleotides
that engage in the splicing reaction into proximity
-RNAs that fold up and have enzymatic activity on their own (catalyze reactions) are called ribozymes
ex. of ribozymes - ANS✅✅self splicing introns
primary transcipts of many genes are alternatively spliced to yield different products - ANS✅✅-the
same RNA transcript can be processed differently in different cell types, or in different conditions
-different proteins can be produced from the same gene transcipt by inclusion or exclusion of
specific exons
-alternative splicing is very common. Ca. 30,000 human gene may encode 64,000-90,000 different
proteins
-can produce multiple transcripts with different functions (alternative splicing)
,insulin receptor is alternatively spliced - ANS✅✅-in RNA processing in the liver, the exons 9-13 are
all included in the messenger RNA and the resulting protein has low affinity for insulin
-this form of the insulin receptor is expressed in tissues that are normally exposed to high levels of
insulin. It is not as sensitive as insulin.
-muscle- missing exon 11
-in RNA processing in skeletal muscle, the codons in exon 11 are excluded from the messenger RNA
and the resulting protein has high affinity for insulin
-this form of the insulin receptor is expressed in tissues that are normally exposed to LOW levels of
insulin. It is more sensitive to insulin (change function of receptor)
genes transcribed from both DNA strands as templates - ANS✅✅-direction of transcription is
determined by the promoter at the beginning of each gene
-genes transcribed from left to right use the bottom DNA strand as the template; those transcribed
from right to left use the top strand as the template
the transcribed RNA molecule - ANS✅✅-has a 5' untranslated region (5' UTR)
-open reading frame specifies the polypeptide chain
-3- untranslated region= 3' UTR
-in prokaryotes, the primary transcript= the messenger RNA (mRNA) (finished product in
prokaryotes)
-in eukaryotes, the primary transcript undergoes further modifications (RNA processing) before it
becomes mRNA
eukaryotic gene structure - ANS✅✅transcription: 5' end-> promoter (transcription start site)->
exons and introns-> stop codon -> termination region -> 3' end
then transcription: 5' exons and introns- 3' UTR
then RNA processing (mRNA transcript)
5'cap-> coding sequence-> stop-> 3' poly A tail (exons and introns get spliced)
RNA processing- 5' cap - ANS✅✅5- cap-> coding sequence-> stop
-5' RNA capped using a modified guanosine linked 5'-5'
-the 5' cap is necessary for the ribosome to bind the mRNA and begin protein synthesis
, -5' cap= modified methylated guanosine
-protects RNA end from degradation
RNA processing- poly A tail - ANS✅✅5' cap-> coding sequence- stop->poly a tail-> 3' OH
-3' end modified by the addition of a sequence called the poly A tail
-poly A tail can be up to 200 A residues long, and is thought to regulate RNA stability
-protects 5' end of RNA
-structure of RNa determines how ling it is
-poly A tail used to extract mRNA by adding poly A
RNA processing-splicing - ANS✅✅-exons and introns-> RNA processing
-mRNA transcript- coding sequence- stop-> poly A trail -> 3' OH
introns - ANS✅✅intervening sequences that are removed by RNA splicing (remember introns
interrupt)
exons - ANS✅✅the coding segments of the gene. Exons are joined to form the coding sequence.
(Exons are expressed)
introns - ANS✅✅interrupt
exons - ANS✅✅expressed
chain initiation and elongation - ANS✅✅-does not start with AUG because not translation
chain termination - ANS✅✅-inverted repeats are characteristic of many termination sites
-RNA polymerase makes RNA
-GC rich because 3H bonds=more stable bonding structure
-the inverted repeats can undergo base pairing and enable the RNA transcript to form a hairpin
structure
transcription does not have to - ANS✅✅be complete before a new transcript is initiated
