Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mutations in humans

  1. Oct 23, 2006 #1
    On average, what percent of the human genecode changes each generation? I know there's somesort of mutation rate, but I haven't studied biology for several years and I'm not exactly sure how to calculate it.
  2. jcsd
  3. Oct 23, 2006 #2

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

    The mutation rate for a generation of cells is given as
    Where h is the number of mutation observed and N is the total number of cell divisions.

    If you tranlsate that to humans, you are interested in the rate as a function of the number of new mutations showing up in the next generation. However, there are lots of problems with this. A large number of spontaneous mutations are fatal to embryo development, for example. So unless you analyzed every premature birth for new defects, you'd miss them. This isn't practical or ethical.

    And I have no idea how you could find all mutations - we're diploid, so a recessive mutation has a large probability of not displaying a trait.
  4. Oct 23, 2006 #3

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

  5. Oct 24, 2006 #4
    "calculated that the per locus rate of mutation for hemophilia in humans is 10^-5 per generation"

    "Comparisons of pseudogenes and of synonymous sites between humans and chimpanzees have suggested mutation rates on the order of 10^-8"


    What do these numbers represent? Base pair substitutions, mutation events?
  6. Oct 24, 2006 #5

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

    Nucleotide changes - for a single allele (DNA sequence that codes for one enzyme). eg. a Thymine becomes an Adenine, for example.
  7. Oct 24, 2006 #6
    So this means there are 1/100000000 nucleotide changes per generation?
  8. Oct 25, 2006 #7

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

    For one allele, or "one gene". Humans have circa 100,000 genes with sometimes hundreds of alleles (possible gene variations for a given locus).

    [lousy assumption alert]

    So, multiply your number times 100,000 and you have a guesstimate of the mutation rate in humans per generation. Since 10^-5 times 10^5 =1
    then the mutation rate over all genes - based on the paper - in humans is about one point mutation (that's what a nucloetide change is) per generation somewhere in all of the human genome.

    [/lousy assumption alert]
    There are other types of mutations, crossovers, deletions, insertions etc.
    (a lot of which are fatal) so it's hard to know the true rate based on looking at only live born people. I do know that Thompson & Thompson Medical Genetics indicates that for 100 live male births there are ~130 conceptions. The spontaeous abortion rates for female fetuses is lower.
    (This is very old data)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Mutations in humans
  1. DNA mutation in humans (Replies: 1)

  2. P53 mutation (Replies: 1)

  3. Mutation balance (Replies: 2)

  4. Evolution and mutation (Replies: 21)