altering sequence of dna bases Flashcards
duplication
Duplication A sequence of DNA bases / nucleotides is repeated / copied
inversion
A sequence of bases detaches from the DNA sequence,
then rejoins at the same position in the reverse order
translocation
A sequence of DNA bases detaches and is inserted at a
different location within the same or a different chromosome
frameshift
occurs when gene mutations (eg. addition, deletion,
change the number of nucleotides by any number not divisible by 3
This shifts the way the genetic code is read, so all the DNA triplets downstream from the mutation change
The sequence of amino acids encoded changes accordingly
the effects on the encoded polypeptide are significant
stem cells
Undifferentiated unspecialised cells capable of:
1. Dividing (by mitosis) to replace themselves indefinitely
2. Differentiating into other types of (specialised) cells
how do stem cells become specialised
● Stimuli lead to activation of some genes
● So mRNA is transcribed only from these genes and then translated to form proteins
● These proteins modify cells permanently and determine cell structure / function
totipotent
Occur for a limited time in early mammalian embryos
● Can divide AND differentiate into any type of body cell
pluripotent
● Found in mammalian embryos (after first few cell divisions)
● Can divide AND differentiate into most cell types (every cell type in the body but not placental cells)
multipotent
● Found in mature mammals
● Can divide AND differentiate into a
limited number of cell types
unipotent
mature mammal
divide differentiate one type of cell
how’s stem cell used to treat human disorder
transplant into paitent
divided into unlimited numbers
then differentiate into required healthy cells
how are Ips produced
Obtain adult somatic cells from patient
Add specific protein transcription factors associated with pluripotency to cells so they express
genes associated with pluripotency
Transcription factors attach to promoter regions of DNA, stimulating or inhibiting transcription
Culture cells to allow them to divide by mitosis
use of stem cells for against
✓ Can divide and differentiate into required healthy cells, so could relieve human suffering by saving lives and improving quality of life
✓ Embryos are often left over from IVF and so would otherwise be destroyed
✓ iPS cells unlikely to be rejected by patient’s immune system as made with patient’s own cells
✓ iPS cells can be made without destruction of embryo and adult can give permission
X Ethical issues with embryonic stem cells as obtaining them requires destruction of an embryo and potential life
X Immune system could reject cells and immunosuppressant drugs are required
X Cells could divide out of control, leading to formation of tumours / cancer
