<span>A photon of UV light causes mutations in the double-stranded DNA via a photochemical reaction. The product of such photochemical reaction in DNA is a cyclobutane pyrimidine dimer. Dimers may be repaired by mechanisms of photoreactivation or nucleotide excision repair (NER), but if the repair doesn’t occur dimers are mutagenic.
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UV light is absorbed by a double bond in pyrimidine bases (thymine and cytosine in DNA). The bond is opened and UV-modified base can now react with neighbouring molecules. If neighbouring molecule is another pyrimidine base, the UV-modified base forms direct covalent bonds with it. A cyclic ring (cyclobutane), not normally found in DNA, is formed (links the two pyrimidines). Next step is forming a single bond between two carbon atoms on the rings.The product of this reaction is a 6-4 molecule pyrimidine-pyrimidone which is more mutagenic than cyclobutane pyrimidine dimers.</span>
<span>Large changes in allele frequencies can occur in a short time.
I'm taking the test now and that's what I know.</span>
An exosystem is a system or environment that surrounds a child and has a high influence on the child's development; however, the child is not directly involved with with the environment. In order to examine exosystems more closely, one may visit places such as medical centers or religious institutions because both of these affect the development of a child's thinking process.
The answer is C
Because it would be that the plants would be resistant over time but that is not a choice
Answer:
a. all tall
Explanation:
If genotypically one of the parents is homozygous dominant and another one is heterozygous for plant height then phenotypically all their progeny will be tall.
Let us suppose, 'T' represents dominant allele and 't' represents recessive allele. Then the genotype of one parent who is homozygous dominant will be TT and genotype of another parent who is heterozygous will be Tt.
The cross is depicted in the attachment.
Here it may also be noted that genotypically two of the progeny will be homozygous dominant while two of the progeny will be heterozygous but phenotypically all the progeny will be 'tall'.
