Answer: B. DNA polymerase checks for errors in base pairing as it helps new DNA strands form.
Explanation: DNA polymerase is an enzyme that catalyzes the synthesis of a new DNA strand from a DNA template. This process is known as replication. During replication, DNA polymerase rejects incorrect bases before the phosphodiester bond is formed because it has a 3' -> 5' exonuclease activity that double checks every nucleotide that is added to the growing strand. This check allows the enzyme to remove a newly added mismatched base pair.
Answer:
In the first step of meiosis I, the chromosomes/genetic material of the cell condenses into a visible form, into a form called heterochromatin. The nucleolus also disappears.
In the second step, a process called synapsis occurs. This is when homologous chromosomes align themselves, gene by gene.
In the third step, crossing over occurs. Segments of corresponding DNA are cut and exchanged between non-sister chromatids of the formed tetrads.
In the fourth step, the nucleus fragments, the nuclear envelope fragments, the two centrosomes (if we're talking about an animal cell) separate from each other as their asters and mitotic spindles (mostly microtubules (kinetochore and non-kinetochore) lengthen. The microtubules extending from the centrosomes can now connect to chromosomes.
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