topic 8 mutations Flashcards
what is a mutation?
change to the base sequence of DNA
what is a substituion?
one or more bases are swapped for another
what is a deletion?
one or more bases are removed
what is an addition?
one or more bases are added
what is a duplication?
one or more bases are repeated
what is an inversion?
sequence of bases is reverse
what is a translocation?
sequence of bases is moved from one location in the genome to another
what does the order of DNA bases in a gene determine?
the sequence of amino acids in a particular polypeptide
what can a change in the amino acid sequence result in?
a change to the tertiary structure
what is a hereditary mutation?
mutation occurs in a gamete so is present in the new foetus
what does degenerate mean?
some amino acids are coded for by more than one DNA triplet
why do not all mutations affect the order of amino acids?
genetic code is degenerate
what is a silent mutation?
where a mutation doesn’t cause a change in the amino acid order
what happens in frameshift?
mutation caused by a deletion or insertion sequence that shifts the way the sequence is read
what do mutagenic agents do?
increase the rate of mutation
what are examples of mutagenic agents?
UV radiation
ionising radiation
some chemicals
some viruses
how can mutagenic agents increase the rate of mutation?
acting as a base
altering bases
changing the structure of DNA
what are stem cells?
unspecialised cells that can develop into other types of cell and become specialised
where are stem cells found?
in the embryo and in some adult tissues
what are totipotent cells?
stem cells that can mature into any type of body cell in an organism
when are totipotent stem cells present in mammals?
in the first few cell divisions of an embryo
what are pluripotent cells?
cells that can specialise to become any cell in the body except the placenta
what are the two types of stem cells present in adult mammals?
multipotent and unipotent
what is a multipotent stem cell?
cell that can differentiate into a few different types of cell
what is a unipotent stem cell?
cell that can only differentiate into one type of cell
how do stem cells become specialised?
stem cells all contain the same genes but in development not all are expressed
mNRA only transcribed from specific genes
the mRNA from these genes is translated into proteins
these modify the cell which leads the cell to become specialised
what are cardiomyocytes?
heart muscle cells that make up a lot of the tissue in our hearts
how can cardiomyocytes be made from unipotent stem cells?
thought that they couldn’t replicate by themselves
some scientists now think old/damaged cardiomyocytes can be replaced by new cardiomyocytes from a small supply of unipotent stem cells in the heart
either slow- some never replaced in a lifetime, or fast- every cardiomyocyte replaced several times
what is an example of how stem cells could be used?
bone marrow has stem cells that can become specialised to form any type of blood cell eg) to treat leukaemia (cancer of blood/bone marrow)
what are the benefits of using stem cells in medicine?
could save many lives
could improve the quality of life for people
what are the three main sources of human stem cells?
adult stem cells
embryonic stem cells
induced pluripotent stem cells
how are adult stem cells obtained?
from the body tissues of an adult
obtained in an operation
can only specialise into a limited range of cells
how are embryonic stem cells obtained?
from embryos in an early stage of development
created in a laboratory using IVF
once embryos approx 4 to 5 days old, stem cells removed, rest of embryo destroyed
can divide an unlimited number of times into all types of body cells
how are induced pluripotent stem cells obtained?
created by scientists in the lab
reprogramme specialised adult body cells so they become pluripotent
express a series of transcription factors that are associated with pluripotent cells- cuase the adult body to express genes associated with pluripotency
what are the ethical issues for stem cell use?
destruction of embryos that could become a foetus
