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The word zygosity may also be used to describe the genetic similarity or dissimilarity of twins. [6] Identical twins are monozygotic, meaning that they develop from one zygote that splits and forms two embryos. Fraternal twins are dizygotic because they develop from two separate oocytes (egg cells) that are fertilized by two separate sperm.
Even monozygotic twins (who develop from one zygote) have infrequent genetic differences due to mutations occurring during development and gene copy-number variation. [1] Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting .
Monozygotic twins carry identical genomic information. Therefore, if they are discordant for a particular disease or phenotype it is likely a result of epigenetic differences. However, unless the twins are studied longitudinally it is impossible to determine if epigenetic variation is the cause of or consequence of disease.
Minisatellites are a type of DNA tandem repeat sequence, meaning that the sequences repeat one after another without other sequences or nucleotides in between them. Minisatellites are characterized by a repeat sequence of about ten to one hundred nucleotides, and the number of times the sequence repeats varies from about five to fifty times.
The missing part is the mapping between the genotype and phenotype space. This leads to a "sleight of hand" (as Lewontin terms it) whereby variables in the equations of one domain, are considered parameters or constants , where, in a full-treatment, they would be transformed themselves by the evolutionary process and are functions of the state ...
Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
Unless the twins live eerily similar lives, those bonds will snap at different temperature points and quickly identify who's who. Police can spot differences between identical twins by melting DNA ...
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.