BIO 208 Midterm exam with correct responses
Post-transcriptional |control |- |correct |answer |-1) |Splicing |RNA |in |various |ways
2) |Modifying |the |life |span |of |mRNAs
3) |alternating |the |rate |at |which |translation |is |initated
4) |activating |or |inactivating |proteins |after |translation |has |occured
Splicesomes |- |correct |answer |-macromolecular |machines |that |splice |primary |transcripts
Alternative |splicing |- |correct |answer |-Means |splicing |the |same |primary |RNA |transcript |in |different
|ways |to |produce |different |mature |mRNAs |and |thus |different |proteins
During |splicing, |gene |expression |is |regulated |with |selected |exons |being |removed |from |the |primary
|transcript |along |with |the |introns. |As |a |result, |the |same |primary |RNA |transcript |can |yield |more
|than |one |kind |of |mature, |processed |mRNA, |consisting |of |different |combinations |of |exons
How |is |alternative |splicing |controlled? |- |correct |answer |-Alternative |splicing |is |controlled |by
|proteins |that |bind |to |RNAs |in |teh |nucleus |and |interact |with |splicesomes |to |influence |which
|sequences |are |used |for |splicing
Importance |of |alternative |splicing |- |correct |answer |-a |gene |used |to |be |considered |a |nucleotide
|sequence |that |encodes |one |specific |protein |or |RNA |along |with |its |regulatory |sequences. |Based |on
|this |view, |estimates |for |number |of |genes |in |the |human |genome |were |typically |in |the |range |of
|60,000 |to |100,000. |However, |once |the |complete |human |genome |sequence |became |available,
|reserachers |have |realized |that |we |may |have |as |few |as |20,000 |sequences |for |primary |mRNA
|transcripts
RNA |interference |- |correct |answer |-RNA |interference |occurs |when |a |tiny |single |stranded |RNA |held
|by |a |protein |complex |binds |to |a |complementary |sequence |in |an |mRNA. |This |event |unleashes
|either |the |destruction |of |mRNA |or |a |block |of |the |mRNA's |translation
How |does |RNA |interference |work? |- |correct |answer |-1) |RNA |polymerase |transcribes |genes |that
|code |for |RNAs |that |double |back |on |themselves |to |form |hairpin
2) |Some |of |the |RNA |is |trimmed |by |enzymes |in |the |nucleus, |then |the |double |stranded |hairpin |that
|remains |is |exported |to |the |cytoplasm
, 3) |in |the |cytoplasm, |another |enzyme |(dicer) |cuts |out |the |hairpin |loop |to |form |double |stranded |RNA
|molecules
4) |One |of |the |strands |from |this |short |RNA |is |taken |up |by |a |group |of |proteins |called |the |RNA
|induced |silencing |complex, |or |RISC. |The |RNA |strand |held |by |RISC |is |a |miRNA
5) |Once |it |is |part |of |a |RISC, |the |miRNA |binds |to |its |complementary |sequences |in |target |mRNA
6) |If |the |match |between |an |miRNA |and |an |mRNA |is |perfect, |an |enzyme |in |RISC |destroys |the |mRNA
|by |cutting |it |in |two
Post-translational |control |- |correct |answer |-Instead |of |waiting |for |transcription, |RNA |processing,
|and |translation |to |occur, |the |cell |can |keep |an |existing |but |inactive |protein |waiting |in |the |wings
|and |then |quickly |activate |it |in |response |to |altered |conditions
Very |fast, |but |energetically |expensive
Targeted |destruction |of |proteins |- |correct |answer |-enzymes |mark |proteins |for |destruction |by
|adding |a |small |polypeptide |called |ubiquitin
Ubiquitin |- |correct |answer |-Ubiquitous |in |cells
Marks |certain |proteins |for |destruction
A |macro |molecular |machine |called |the |proteasome |recognizes |proteins |that |have |a |ubiquitin |tag
|and |cuts |them |into |short |segments
DNA |packaging, |Eukaryotes |vs. |prokaryotes |- |correct |answer |-The |chromatin |of |eukaryotic |DNA
|must |be |decondensed |for |basal |and |regulatory |transcription |factors |to |gain |access |to |genes |and |for
|RNA |polymerase |to |initiate |transcription. |The |tight |packaging |of |eukaryotic |DNA |means |that |the
|default |state |of |transcription |in |eukaryotes |if |"off". |In |contrast, |the |default |state |of |transcription |in
|bacteria, |which |lack |histone |proteins |and |have |freely |accessible |promoters |is |"on"
Complexity |of |transcription; |Eukaryotes |vs. |prokaryotes |- |correct |answer |-Transcriptional |control |is
|much |more |complex |in |euaryotes |than |in |bacteria. |The |sheer |number |of |eukaryotic |proteins
|invovled |in |regulating |transcription |dwarfs |that |in |bacteria, |as |does |the |complexity |of |their
|interactions
Coordinated |transcription, |Eukaryotes |vs. |prokaryotes |- |correct |answer |-in |bacteria, |genes |that |take
|part |in |the |same |cellular |response |are |often |organized |into |operons |and |transcribed |together |from
|a |single |promoter. |In |contrast, |operons |are |rare |in |eukaryotes. |Instead, |for |coordinated |gene
|expression, |eukaryotes |rely |on |the |strategy |used |in |bacterial |regulons |(physically |scattered |genes
Post-transcriptional |control |- |correct |answer |-1) |Splicing |RNA |in |various |ways
2) |Modifying |the |life |span |of |mRNAs
3) |alternating |the |rate |at |which |translation |is |initated
4) |activating |or |inactivating |proteins |after |translation |has |occured
Splicesomes |- |correct |answer |-macromolecular |machines |that |splice |primary |transcripts
Alternative |splicing |- |correct |answer |-Means |splicing |the |same |primary |RNA |transcript |in |different
|ways |to |produce |different |mature |mRNAs |and |thus |different |proteins
During |splicing, |gene |expression |is |regulated |with |selected |exons |being |removed |from |the |primary
|transcript |along |with |the |introns. |As |a |result, |the |same |primary |RNA |transcript |can |yield |more
|than |one |kind |of |mature, |processed |mRNA, |consisting |of |different |combinations |of |exons
How |is |alternative |splicing |controlled? |- |correct |answer |-Alternative |splicing |is |controlled |by
|proteins |that |bind |to |RNAs |in |teh |nucleus |and |interact |with |splicesomes |to |influence |which
|sequences |are |used |for |splicing
Importance |of |alternative |splicing |- |correct |answer |-a |gene |used |to |be |considered |a |nucleotide
|sequence |that |encodes |one |specific |protein |or |RNA |along |with |its |regulatory |sequences. |Based |on
|this |view, |estimates |for |number |of |genes |in |the |human |genome |were |typically |in |the |range |of
|60,000 |to |100,000. |However, |once |the |complete |human |genome |sequence |became |available,
|reserachers |have |realized |that |we |may |have |as |few |as |20,000 |sequences |for |primary |mRNA
|transcripts
RNA |interference |- |correct |answer |-RNA |interference |occurs |when |a |tiny |single |stranded |RNA |held
|by |a |protein |complex |binds |to |a |complementary |sequence |in |an |mRNA. |This |event |unleashes
|either |the |destruction |of |mRNA |or |a |block |of |the |mRNA's |translation
How |does |RNA |interference |work? |- |correct |answer |-1) |RNA |polymerase |transcribes |genes |that
|code |for |RNAs |that |double |back |on |themselves |to |form |hairpin
2) |Some |of |the |RNA |is |trimmed |by |enzymes |in |the |nucleus, |then |the |double |stranded |hairpin |that
|remains |is |exported |to |the |cytoplasm
, 3) |in |the |cytoplasm, |another |enzyme |(dicer) |cuts |out |the |hairpin |loop |to |form |double |stranded |RNA
|molecules
4) |One |of |the |strands |from |this |short |RNA |is |taken |up |by |a |group |of |proteins |called |the |RNA
|induced |silencing |complex, |or |RISC. |The |RNA |strand |held |by |RISC |is |a |miRNA
5) |Once |it |is |part |of |a |RISC, |the |miRNA |binds |to |its |complementary |sequences |in |target |mRNA
6) |If |the |match |between |an |miRNA |and |an |mRNA |is |perfect, |an |enzyme |in |RISC |destroys |the |mRNA
|by |cutting |it |in |two
Post-translational |control |- |correct |answer |-Instead |of |waiting |for |transcription, |RNA |processing,
|and |translation |to |occur, |the |cell |can |keep |an |existing |but |inactive |protein |waiting |in |the |wings
|and |then |quickly |activate |it |in |response |to |altered |conditions
Very |fast, |but |energetically |expensive
Targeted |destruction |of |proteins |- |correct |answer |-enzymes |mark |proteins |for |destruction |by
|adding |a |small |polypeptide |called |ubiquitin
Ubiquitin |- |correct |answer |-Ubiquitous |in |cells
Marks |certain |proteins |for |destruction
A |macro |molecular |machine |called |the |proteasome |recognizes |proteins |that |have |a |ubiquitin |tag
|and |cuts |them |into |short |segments
DNA |packaging, |Eukaryotes |vs. |prokaryotes |- |correct |answer |-The |chromatin |of |eukaryotic |DNA
|must |be |decondensed |for |basal |and |regulatory |transcription |factors |to |gain |access |to |genes |and |for
|RNA |polymerase |to |initiate |transcription. |The |tight |packaging |of |eukaryotic |DNA |means |that |the
|default |state |of |transcription |in |eukaryotes |if |"off". |In |contrast, |the |default |state |of |transcription |in
|bacteria, |which |lack |histone |proteins |and |have |freely |accessible |promoters |is |"on"
Complexity |of |transcription; |Eukaryotes |vs. |prokaryotes |- |correct |answer |-Transcriptional |control |is
|much |more |complex |in |euaryotes |than |in |bacteria. |The |sheer |number |of |eukaryotic |proteins
|invovled |in |regulating |transcription |dwarfs |that |in |bacteria, |as |does |the |complexity |of |their
|interactions
Coordinated |transcription, |Eukaryotes |vs. |prokaryotes |- |correct |answer |-in |bacteria, |genes |that |take
|part |in |the |same |cellular |response |are |often |organized |into |operons |and |transcribed |together |from
|a |single |promoter. |In |contrast, |operons |are |rare |in |eukaryotes. |Instead, |for |coordinated |gene
|expression, |eukaryotes |rely |on |the |strategy |used |in |bacterial |regulons |(physically |scattered |genes
