GENETICS AND EVOLUTION
GENETIC BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The conditions within the uterus can be different for each, affecting phenotype.
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They may have different alleles.
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One twin may have more dominant alleles than the other.
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Two eggs may have been fertilized at the same time.
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Detailed explanation-1: -While identical twins form with the same set of genes, human development is not just genetic. The environment also has an impact. 1 So, beginning in the early environment of the womb, external influences can change the appearance of twins. For example, some monozygotic twins share a placenta.
Detailed explanation-2: -Some identical twins can have different heights and weights. This is because height and weight are controlled by what you eat as well your DNA. Differences in diet can start earlier than you might imagine. When the twins are growing inside the uterus, there can be differences in how well they connect to the placenta.
Detailed explanation-3: -As a result of the environment, chemicals called “epigenetic marks” attach to the chromosomes and can turn specific genes on or off. So identical twins with identical DNA may have different genes turned on, causing them to look and act differently, and even to develop different diseases such as cancer.
Detailed explanation-4: -That’s because so-called identical twins pick up genetic mutations in the womb, as their cells weave new strands of DNA and then split into more and more cells. On average, pairs of twins have genomes that differ by an average of 5.2 mutations that occur early in development, according to a new study.
Detailed explanation-5: -Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar.