Biology and DNA mutations?

Question

Cells proofread and repair errors in the genetic information encoded in DNA. But some lasting mistakes, or mutations, still happen. The most error-prone stage in DNA replication occurs after parent DNA strands have seperated but before new complementary strands are in place. Why might permanent errors be more likely then?

Answer 1

I actually went over this recently, in my AP Bio class. My book actually explained that because there are so many genes that need to be replicated, either of the enzymes, DNA Polymerase, or ligase that combines the okazaki fragments, can miss out a gene, and put a different one.

As we all know, according to Chargaff rule, he said that the amount of Guanine= to cytosine, and the amount of Thymine=to adenine. Although these composition is always consistent, they have different patterns, and during replication there could happen a mistake, that is extremely rare though. One in a billionth of probability that this could happen if the enzymes are working properly. If the enzymes aren't then 1/10,000 can happen a mistake, which is unfortunate. That only could happen if the woman who is pregnant is drinking, smoking, and doing all those unhealthy stuff.

Anyway, for example, say that the proper sequence for a DNA of the parent strand is GCC. That means that the other strand has to complement these genes. There's suppose to be one cytosine, and two Guanine combined. However, instead the sequence of GCC, the enzymes can rearange the genes differently. Instead of having the "G" first, they are puting the "G" second, making CGC, making a different meaning, which could be lethal or harmful, or a very mild mistake depending on what the three genes would transcripe into to make a mRNA and create nucleotides through translation, which make up chains of polypeptides.

By the way, the straight forward answer to your question is because of the amount of genes that suppose to be replicated, and because of the speed of replication, which is very fast. The enzymes even if they check for errors, they still can make an error. Fortunately enough, this happens very rarely.

Answer 2

Permanent errors could be like a glitch in the system, say, for example, the parent have some type of ailment that could possibly affect the process happening. Another aspect is that the codes could have an error to begin with, like a mother/father host only giving off 23 chromosomes instead of 24, making the match a bit uneven (usually 24 to 24) but in reality these "mutations" might be an advantage, take, the Mule for example. Its a mixture between the Horse and the Donkey and it is created because they have different numbers of chromosomes. The final aspect is that nothing is perfect. The DNA strands only proofread to repair the errors once or twice, but it still might have missed a discreet error, causing such changes to happen and last.

Answer 3

Because the DNA proofreading works on double stranded DNA only.

Answer 4

Well, the cell would have a different DNA makeup, so, the cell will change accordingly to the DNA because the DNA is what tells the cells what to do. The typical cell would be mutated.