What must occur before replication can begin?

The two DNA strands must separate

Explanation:

This separation is mediated by DNA helicases enzymes. Using ATP energy, they breakdown the hydrogen bonds between the two strands of the double helices giving access of DNA polymerase to single-stranded DNA required for replication. The DNA polymerase can only bind to single-stranded DNA.

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

no u