Exercise 2

Question 1

2. How do the chromosomes physically appear in between cell divisions.

Answer 1

2. In between cell divisions chromosomes appear as long, fine thread-like structures intertwined in a mass referred to as chromatin or chromatin net. These structures cannot be seen even with a light microscope.

Question 2

3. How do the chromosomes physically appear as cell division begins?

Answer 2

3. As cell division begins the chromatin changes its form, shortening, thickening and forming very compact and coiled rod-like structures. These structures are now referred to as chromosomes and can be seen with a light microscope.

Question 3

4. List the four steps involved in DNA replication.

Answer 3

4. The four steps involved in replication are:
   i) hydrogen bonds between the nitrogen containing bases of the two strands of DNA break and the double helix unwinds and unzips
   ii)new nucleotides fit into the place where the original ones were, using the base- pairing rule
   iii)the new nucleotides join together with the help of an enzyme
   iv)the end result is two complete DNA molecules identical to each other and to the original DNA molecule. Within each DNA molecule is one parental strand from the original DNA molecule and one daughter strand that is new.

Question 4

5. What is a mutation?

Answer 4

5. A mutation is an error during replication that is not corrected but persists becoming a permanent change.

Question 5

6. What is the function of RNA?

Answer 5

6. The function of RNA is to act as a helper to DNA, allowing protein synthesis to occur according to the genetic information that DNA provides.

Question 6

7. How many types of RNA are there and what is the name given to each?

Answer 6

7. There are three types of RNA: ribosomal RNA (rRNA), messenger RNA (mRNA) and transfer RNA (tRNA)

Question 7

8. Where is rRNA produced, and where and how does it function?

Answer 7

8. rRNA is produced in the nucleolus of the nucleus from a portion of the DNA molecule that acts as a template or blueprint. rRNA combines with protein to form the subunits that make up the organelles referred to as ribosomes. These subunits are made in the nucleus of the cell and then relocate to the cytoplasm where protein synthesis will occur at the ribosomal sites.

Question 8

9. Where are ribosomes found, and what happens at the ribosome?

Answer 8

9. Ribosomes are generally found along the endoplasmic reticulum, and this structure is then referred to as rough endoplasmic reticulum. Some ribosomes are found free within the cytoplasm or in clusters called polyribosomes. Protein synthesis occurs at the ribosome.

Question 9

10. Where is mRNA produced, and where and how does it function?

Answer 9

10. mRNA is produced in the nucleus. A short section (gene) of one strand of the DNA molecule is its blueprint, and this new molecule formed of codons then travels into the cytoplasm and locates at the ribosome.

Question 10

11. Where is tRNA produced, and where and how does it function?

Answer 10

11. tRNA is produced in the nucleus. The second strand of DNA is its blueprint forming triplets called anticodons. These new molecules then travel into the cytoplasm bonding with their corresponding amino acid. Each type of tRNA bonds with only one type of amino acid. The tRNA’s with their joined amino acid then travel to the ribosome. At the ribosome the nitrogen containing bases of the tRNA and mRNA will join together according to the base-pairing rule (codon to anticodon).

Question 11

Where is DNA found mostly?

Answer 11

1. DNA is mostly found within chromosomes which in turn are found within the nucleus of a cell.