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Biology 206- Genetics > Chapter 18- Unit 4 > Flashcards

Chapter 18- Unit 4 Flashcards

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1
Q

what is alternative splicing?

A

it is the ability to produce different proteins from the same mRNA by splicing together different combinations of exons

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2
Q

what kind kind of example is calcitonin/calcitonin gene-related peptide gene (CT/CGRP)

A

alternative splicing

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3
Q

what is the function of calcitonin in the thyroid gland

A

it reduces blood calcium levels

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4
Q

what is the function of calcitonin gene-related peptide gene (CT/CGRP) in neurons?

A

it dilates blood vessels

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5
Q

how many poly A tails are there in the primary transcript

A

there are 2 tails; 1st one b/w 4 and 5; 2nd one after 6

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6
Q

what is myotonic dystrophy (DM)

A

it is an autosomal Dominican condition characterized by myotonia, insulin resistance, cataracts, intellectual disability, and cardiac muscle problems

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7
Q

what kind of example is myotonic dystrophy (DM)

A

alternative splicing

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8
Q

what is DM1

A
  • a type of myotonic dystrophy

- the DMPK gene >150 copies of a CTG repeat (aka a tri-nucleotide repeat expansion disease)

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9
Q

what is DM2

A
  • a type of myotonic dystrophy

- the CNBP gene has >11,000 copies of a CCTG repeat ( a tetra-nucleotide repeat)

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10
Q

what is DM caused by

A

it is caused by the build-up of the RNAs in the nucleus, which interfere with alternative splicing regulators important in muscle and neuron function

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11
Q

In eukaryotic mRNA what happens if the 5’ cap or the 3’ poly-A tail are lost?

A

it would result in degradation

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12
Q

what are the two mechs of mRNA decay

A
  1. deadenylation -dependent decay

2. deadenylation-independent decay

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13
Q

what does deadenylation-dependent decay do?

A

degrading euk mRNA by removing 5’ cap and 3’ poly-A tail

  1. deadenylase shortens poly-A tail
  2. exoribonuclease shortens poly-A tail in 3’ to 5’ direction
    3decapping enzyme takes off the 5’ cap
  3. exoribonuclease (XRN1) degrades in the 5’ to 3’ direction
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14
Q

what does deadenylation independent decay do?

A

degrading euk mRNA by just taking off the 5’ cap

  1. decapping enzyme takes odd 5’ cap
  2. exoribonuclease (XRN1) degrades in the 5’ to 3’ direction
  3. endoribonuclease cuts mRNA into bits (interanlly)
  4. exoribonuclease starts to break up the unprotected fragments that are made from step 3
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15
Q

what is nonsense mediated decay?

A

a cellular response in which mRNA is degraded if it contains a premature termination codon (PTC)

  1. Exon junction complex ( EJC; in b/w exons; leave after translation) proteins promote the recruitment of Upf
  2. Upfs activate de-capping enzyme (removes 5’ cap)
  3. exonuclease/endonuclease degrade mRNA (make mRNA vulnerable)
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16
Q

what are small ncRNA (sncRNA; snickers)

A

the are double stranded RNA molecules with short 3’ overhangs (20-31 nt long)

17
Q

what are the two types of sncRNAs?

A
  1. microRNAs (miRNAs; endogenous)

2. small interfering RNAs (siRNAs; exogenous)

18
Q

wha are micro RNAs (miRNAs) and what do they do?

A

they are a type of RNA that is encoded in the genome and they regulate the expression of other genes

19
Q

what is RNA interference

A

it is a mech where sncRNA molecules tell the post-transcriptional silencing of mRNAs in a sequence-specific manner meaning they become slightly complementary to the messenger RNA (mRNA)

20
Q

what do both miRNA and siRNA result in after RNA interference

A

results in a gene knockdown= knocking down the expression of a gene
by……

  1. triggering mRNA degradation
  2. inhibiting mRNA translation
21
Q

what is the pathway for miRNA in rna interference

A
  1. miRNA genes are expressed to make primary miRNA (nucleus)
  2. drosha enzyme cuts primary mmiRNA to make pre-curose miRNA (and then enters cytoplasm) (nucleus)
  3. dicer cuts the pre-curseor miRNA to shorten miRNA
  4. RISC (rna induced silencing complex) binds to double stranded miRNA
    • AGO (silncer) removes 1 strand, and keeps the other
      1. strand=partially complementary= translation is inhibited
      2. strand= totally complementary= mRNA is degraded by RISC
22
Q

what is the pathway for siRNA in RNA interference

A
  1. dicer cuts the pre-curseor siRNA to shorten siRNA
  2. RISC (rna induced silencing complex) binds to double stranded siRNA
    • AGO (silncer) removes 1 strand, and keeps the other
      1. strand=partially complementary= translation is inhibited
      2. strand= totally complementary= mRNA is degraded by RISC
23
Q

what are long ncRNAs (lncRNAs; long nickers)

A

they are double stranded RNA molcuces (> 200 nt long)

24
Q

what is a function of lncRNAs

A

they function as competing endogenous RNAs (ceRNAs) and it is where they act as “sponges” and “soak up” miRNAs

25
Q

what is an example of a lncRNA functions as a ceRNA

A

duchenne muscular dystrohpy

  • linc-MD1 is low which allows for miR-133 and miR-135 to bind and to prevent the translation of these RTF
    • could add more linc-MD1 to cure this (maybe)
26
Q

what is an example of lncRNAs

A

the X inactivation by the lncRNA Xist

- causes the entire chromosome to be inactivated

27
Q

who were the people who showed one of the first examples of RNAi

A

Andrew Fire and Craig Mello

28
Q

what does mex-3 RNA do in c.elegan embryos

A

this RNA is expressed formally and when it does this it plays a role in development

29
Q

what is mex-3 antisense

A

it is the strand that is complementary to sense mex-3 mRNA

30
Q

what were the conditions of the cells in the RNAi experiment

A

have 4 cells

  1. normal
  2. endogenous mex-3 RNA
  3. injected with mex-3 antisense RNA
  4. injected with sense and antisense dsRNA
31
Q

what was the result from the RNAi exxperiment

A
  • when the cell is injected with antisense it losses expression for mex-3 RNA but not completely
  • when the cell is injected with sense and antisense dsRNA there is no expression of the mex-3 RNA
32
Q

once the cells are injected with stuff in the RNAi experiment what happens next

A
  1. the embryos are put into in situ hybridization
  2. a labeled probe is added that is complementary to mex-3 RNA
  3. if the cell expresses mex-3 RNA that mRNA in the cells will bind to the probe and become labeled
33
Q

how can the Xist cause the entire X chromosome to become inactivated

A

Xist can cover many regions on the X chromosome

34
Q

once the X chromosome is inactivated what happens to it

A

The X chromosome is coated by a stable Xist and it silences and condenses the X chromosome making it into a Barr body

Biology 206- Genetics (4 decks)

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