BIO U2 W16

36 flashcards · Biology · by Michael Katsikas

  1. Differentiation

    The process in which cells become specialized in structure and function

  2. Some genes that code for enzymes are expressed in all cells ("Housekeeping genes"). Suggest what proceses theses enzymes might be involved in?

    - respiration - transcription - translation

  3. State 2 main features of stem cells

    - undifferentiated but can differentiate into specialised cells - they can replace themselves

  4. Why can stem cells differentiate into different cells?

    Because they are capable of translating more of their DNA

  5. Cells that can divide and produce any type of body cell

    Totipotent cells

  6. What can totipotent cells do that results in cell specialisation?

    during development, they translate only part of their DNA

  7. When do totipotent cells occur in mammals?

    for a limited time, only as embryos

  8. Cells that can divide in unlimited numbers and can differentiate into almost any type of specialised cell

    pluripotent

  9. What can pluripotent cells not differenciate to?

    Placenta tissue

  10. What can pluripotent cells not differenciate to?

    found in mature adults, can divide to form only a limited number of different cell types

  11. Where are multipotent cells abundant?

    - bone marrow (blood cell) - umbilical cord and fetus

  12. Unipotent stem cells

    found in mature mammals and are derived from multipotent cells. They can only differentiate into one cell type

  13. adult stem cells

    uni and multipotent

  14. embryonic stem cells

    pluripotent and totipotent

  15. What can be used as an alternative instead of pluripotent cells in treating human disorders

    multipotent cells, sourced from adult tissue sucha as bone marro or umbilical cords

  16. Why is it better to use embryonic stem cells than adult stem cells?

    They are much easier to manipulate and aquire

  17. Ethical arguments for the use of embryonic stem cells

    - no resemblance to a human being (legally speaking, if an ambryo cannot be sistinguished as being that of a human, it is not a "person"). - wrong to allow human suffering to continue when there are ways of alleviating it - makes no sense to destroy spare embryos that otherwise would not be used

  18. Ethical arguments against the use of embryonic stem cells

    - undermines respect for human rights - potential life - wrong to use humans as a means to an end - embryos are unable to give consent, adult stem cells are given with consent

  19. cells that are produced from differienciated adult body cells that have been altered in a laboratory

    Induced pluripotent stem cells

  20. What does the inducing of pluripotent cells involve

    the use of specific protein transcriptional factors to reprogramme the cells causing them to take on the characteerisitics of pluripotent cells and self-renewal

  21. What is a transcription factor?

    Protein(s) that control the rate of protein synthesis by switching genes on/off

  22. What is a promoter region?

    A short sequence of DNA at the start of a gene ( the bit that RNA polymerase attaches to)

  23. How does an activator transcription factor function?

    Transcription factors move from cytoplasm into the nucleus. Binds to the promoter region Helps RNA polymerase bind to DNA Gene is transcribed.

  24. How does a repressor transcription factor function?

    Transcription factors move from cytoplasm into the nucleus. Binds to the promoter region Prevents RNA polymerase bind to DNA Gene is NOT transcribed.

  25. What is the mechanism of oestrogen controlling transcription factors?

    Oestrogen is a steroid hormone. Binds to receptor called oestrogen receptor Forms an oestrogen - oestrogen receptor complex. Enters cytoplasm via cell surface membrane Binds to receptor in cytoplasm Receptor-hormone complex passes through nuclear envelope and enters nucleus Complex binds to receptor bound to DNA Transcription activated at point of binding Protein synthesis, cell proliferation Oestrogen becomes dissociated from its receptor and leaves the nucleus/cell

  26. Explain the meaning of epigenetics

    Changes to the gene expression caused by environmental factors without changes to the DNA base sequence.

  27. Explain how methylation of DNA affects gene expression?

    More methylation terminates transcription Methyl group attaches to CpG sites Transcription factors prevented from attaching Gene prevented from transcription and not expressed.

  28. Explain how acetylation of DNA affects gene expression?

    Less acetylation terminates transcription Increased positive charge on histones Increased attraction to phosphate groups on DNA Stronger assosication of DNA and histones More tightly coiled Transcription factors prevented from attaching therefore gene is not expressed

  29. Explain how siRNA prevents gene expression

    Prevents translation Short double stranded RNA Combines with a protein to form a SiRNA- protein complex SiRNA becomes single stranded Has complementary base pairs to target mRNA so binds to it SiRNA- protein complex breaks down mRNA into pieces prevents translation

  30. Explain how microRNA prevents gene expression.

    Combines with a protein to form microRNA - protein complex Binds to mRNA by complementary base pairing Prevents ribosome attachment prevents translation

  31. Explain how hypermethylation causes uncontrollable cell division

    Tumour suppressor cells which normally slow down the rate of cell division cause uncontrollable cell division because the proteins are not transcribed and expressed due to increased methylation

  32. Explain how hypomethylation causes uncontrollable cell division.

    Proto- oncogenes which normally speed up the rate of cell division undergo decreased methylation which causes more proteins to be transcribed causing uncontrollable cell division.

  33. Explain the term proteome

    The complete set of proteins that an organism can make

  34. What is histone modification?

    Chemical groups can be added to amino acids in histone structure to alter chromatin folding Makes chromatin fold "tighter" which makes it harder to transcribe or "looser" to make it easier to transcribe

  35. Describe the acetylation process

    histone acetyl-transferase adds acetyl groups to the amino acid lysine which neutralises its positive charge resulting in less attraction of the histones to the negative charge of dna therefore chromatin decondenses. transcription factors have access to the dna and bind to the promotor region leading to expression of the gene.

  36. apoptosis

    process of programmed cell death.