Lecture cycle 8

• What is the difference between differential and temporal gene expression?

  - differential expression: different tissues express different genes

  - temporal expression: when expression changes according to time
• What are the various levels of regulation? (transcriptional, posttranscriptional, translational and posttranslational).


  -transcriptional: determines which genes are transcribed

  -posttranscriptional: determines types and availability of mRNAs to ribosomes

  -translational: determines rate at which proteins are made

  -posttranslational: determines availability of finished proteins
• How does the lac operon work?

  the lac repressor binds to the operator to stop the transcription when there is no lactose
• What are the functions of lacZ and lacY?

  -lacZ: codes for beta- glactosidase which converts lactose to galactose and glucose

  -lacY: codes for permease which is a membrane transport protein
• How are genes differentially expressed in different cell types?

  tissue specific transcription factors
• How do tissue-specific transcription factors in the cell lead to spatial and temporal gene expression?


  they determine where the specific gene will be transcribed and when the genes will be transcribed
• Where might the transcription factors be found in the cell?


  cytoplasm
• What enzyme splices pre-mRNA?

  spliceosomes (SNRPs)
• What is the 3' splice site that is recognized?

  NCAGG
• How might mutations in 5' and 3' splice site lead to mutation?

  - they may change the reading frame, resulting in the wrong areas being spliced
• How do mutations in the intron lead to beta-thalassemia?

  the G to A mutation leads to a mutated 3' splice site, resulting in splicing too early and abnormal formation of the beta-globin protein
• What does telomerase do?

  catalyzes the lengthening of telomeres in telomerase active cells
• Why is telomerase activated in cancer cells and why is it present in stem cells?

  -cancer cells: to prevent them from shortening and leading to cell death

  -stem cells: stablize the length of the genome so they don't senescence
• What is a hayflick limit?


  the number of times a somatic cell can divide before it reaches senescence
• What is cell senescence?

  when cells stop dividing, but can carry out functions
• What is temporal regulation?

  control of genes at different times
• What is spatial regulation?


  control of genes in different tissues
• How do mutations in the 5' and 3' splice sites lead to formation of mutated mRNA and proteins?

  -affect what sequences are transcribed [intronic sequence interpreted as exonic sequences]

  -can lead to premature termination of translation resulting in a shorter protein
• How does splicing error lead to abnormal production of the beta-globin protein in beta-thalassemia.

  a point mutation lead to a premature 3' splice site recognition sequence, resulting in splicing too early
• How are ApoB100 and ApoB48 formed during RNA-editing? What is this a type of?

  -ApoB48 mRNA gets edited resulting in a shorter protein [deamination] as a result of a new stop codon, this leads to ApoB48 being synthesized in the small intestine
• How can we develop from a one cell zygote?

  pluripotent stem cells
• What are stem cells? What are the different types and their properties?

  -stem cells have the ability to differentiate into different cell types

  -embryonic

  -somatic: regenerate tissues

  -induced pluripotent: somatic cells induced into stem cells

  -umbillical cord
• What are the makes different types of stem cells?

  varying potency

  -totipotent: differentiate into embroyonic and extra embryonic cell types

  -pluripotent: descendants of totipotent, can differentiate into nearly all cells

  -multipotent: differentiate into closely related family of cells

  -unipotent: produce one cell type but can self renew
• What is an adult stem cell? What are examples of them and their properties?

  -somatic stem cells

  -stored in the niche

  -have self-renewal properties

  -ex. bone marrow stem cells
• What are ways that a stem cell could divide?

  -symmetric self-renewal: two stem cells are produced

  -assymmetric self-renewal: one stem cell and one pregenitor is produced

  -symmetric differentiation: two progenitors are produced
• What is the difference between stem cells and progenitor cells?

  -progenitor cells are committed to differentiating

  -stem cells can replicate indefinetly
• What is the difference between a multipotent progenitor and committed progenitor?

  multipotent: from bone marrow stem cells, have large potency

  committed: develop into specific cell type
• What is the role of epidermal stem cells in the skin

  then move from the basal layer to wherever they are needed
• How are cells regenerated in the small intestine?

  stem cells stored in niche are activated by the release of transcription factors
• What phase of the cell cycle are stem cells resting in? How do they reenter the cell cycle?

  -resting in G0

  -activated by transcription factors
• How do you test for potency of stem cells?
• How are iPS cells are made?

  -take an adult fibroblast cell, reprogram using transcription factors to create iPS cells, these cells then go to differentiate
• how are iPS cells used in therapy?

  take stem cells from the patient and turn them into iPS cells, these then differentiate into the specific cells needed to combat the illness
• What were two major things that iPS cells were used to treat?

  - Macular degeneration

  - burn victims
• How are iPS cells used to treat sickle cell and beta thalassemia? How is this process connected to personalized medicine and application of pharmacogenetics?

  - CRISPR edit the stem cells

  - mutate the enhancer that BC11A cannot bind

  - put into bone marrow so we can produce red blood cells with fetal hemoglobin
• What are the key ideas in the "New England Journal of Medicine" study we covered in class?

  that you can use CRISPR Cas9 edited stem cells to treat sickle cell and beta thalassemia