Question

What features of DNA replication cause each new DNA molecule to be exactly like the original? (1pt)

    

C. Why is replication an important cell process? (1pt)

    

Point Mutation

A. How does the point mutation that you made change the DNA code on your molecule? (2pts)

B. Referring to your textbook, explain how mutations can occur in cells and how such changes might affect an organism with the mutation. (2pts)

Answer 1

1) DNA replication in a cell is semi-conservative. Each new strand is synthesized anti-parallel and complementary to the original DNA strand. This complementary base pairing of Adenine with thymine and Guanine with Cytosine is responsible for the identical nature of newly synthesized DNA with the original, since the old strands of DNA act as template for complementary synthesis of the new DNA strand which is synthesized in a 5'-->3' direction, antiparallel to the original DNA strand.

2) DNA replication is important for the continuation of species. If replication did not take place, then with every cell division consisting of meiosis or mitosis, the DNA in the cell will go on reducing which will lead to loss of genetic information in the cell. The genetic makeup of an organism resides in it's DNA, DNA directs the growth and development of any organism. Thus, any loss of DNA will lead to a loss of information that is pertinent to the survival and continuation of the species. DNA replication is thus a very procedure that maintains the integrity of genetic information stored in DNA and ensures the continuation of species.

3) Point mutations refer to change in a single base of DNA. This change can affect the entire DNA sequence. Point mutation leading to changing of a purine base with a pyrimidine base in DNA can affect transcription of the mutated gene which will ultimately affect translation of the gene in popypeptide. A point mutation may lead to premature stop in transcription of the gene, or it may change the amino acid sequence of the polypeptide leading to formation of a faulty protein. Genetic codons are triplet in nature. A point mutation is any of the base of the triplet codon will lead to changing of said codon. For example, a point mutation in codon TGT to change it to TGA will lead to change in the complete genetic sequence, since TGT codes for cysteine amino acid while TGA codes for stop codon. Similarly, mutation of TGT to TGG will lead to chnage iamino acid since, TGG codes for tryptophan amino acid. Thus, a simple point mutation can change the complete getic sequence.

4) Mutations can occur spontaneously in cells or due to exposure of any muatgen such as UV-rays or X-rays or any chemicals such as ethidium bromide etc. Mutations can also be obtained when there is a mutation in the genetic information contributed from the sperm or egg. Majority of the mutations in a cell occur in non-coding region of the DNA which do not really affect the organism, however, if the mistake is in the coding region, protein synthesis could be altered, which can affect many processes if certain proteins aren’t being produced.