Clark Larsen Answers Students FAQs

1. Question: What are the different types of genes?

Response: Structural genes are those that are responsible for the physical structures of the body. For example, hair, skin color, blood type, and eye shape are all due to the function of structural genes. Regulatory genes are those that are responsible for turning on and off other genes. They regulate the timing of gene activities. For example, regulatory genes determine when large amounts of testosterone and estrogen should be produced, initiating the process of puberty. A special type of regulatory gene is the homeotic or Hox genes. These genes are essential in embryological development, determining where the regions of the body should be. Scientists have studied these genes in fruit flies. By purposely mutating the Hox genes, they have produced flies with legs or eyes in the place of antennae.

See Figure 3.21 Homeotic (Hox) Genes

 

2. Question: How does protein synthesis work?

Response: Protein synthesis begins with the replication in the nucleus. A segment of DNA is used as a template to form messenger RNA. This segment codes for a particular protein. Once complete, the messenger RNA leaves the nucleus and goes to the ribosomes. At the ribosomes, the messenger RNA is read in groups of three nitrogen bases, known as codons. Read one codon at a time, a transfer RNA inserts the amino acid it’s carrying into the protein chain if it has the complementary anticodon. As the next codon is read, a transfer RNA with the complementary anticodon adds the next amino acid to the chain. When a “stop” codon is reached, the protein is completed and released from the ribosomes.

See Figure 3.19 Protein Synthesis, part 1

See Figure 3.19 Protein Synthesis, part 2

 

3. Question: What is the difference between mitosis and meiosis?

Response: Mitosis is cell division that creates identical somatic cells, each with two sets of chromosomes (paired). Mitosis occurs throughout life, as it is used in growth and to replace dead cells. Meiosis is cell division that creates gametes, each with only one set of chromosomes (unpaired). Mitosis involves one DNA duplication followed by one cell division. Two daughter cells are produced from the mitotic division of one parent cell. Meiosis involves one DNA duplication, followed by two cell divisions. Four gametic cells are produced from the meiotic division of one parent cell. In males, all four of these gametic cells eventually become sperm; in females, however, only one of the four gametic cells will become a functional ovum.

See Figure 3.14 Mitosis

See Figure 3.15 Meiosis

 

4. Question: What are the law of independent assortment and the law of segregation?

Response: Mendel’s Law of Independent Assortment states that each genetic trait is inherited separately. For example, hair color is inherited separately from eye shape. However, this only applies to genes located on different chromosomes. Those genes located on the same chromosome are said to be “linked” because chromosomes are inherited as a unit. You inherit one chromosome from each of your mother’s pairs and one chromosome from each of your father’s pairs.

See Figure 3.23 Law of Segregation

 

5. Question: What are prokaryotes and eukaryotes and what is their basic structure?

Response: Prokaryotes are organisms that do not have a membrane-bound nucleus containing DNA or other membrane-bound organelles. Its DNA is not organized into chromosomes. Most prokaryotes are unicellular, but some are multicellular. Prokaryotes include bacteria and blue-green algae. Eukaryotes are unicellular and multicellular organisms with a distinct, membrane-bound nucleus containing DNA, packaged as chromosomes. Eukaryotes are typically larger than prokaryotes and contain membrane-bound organelles, such as mitochondria. Eukaryotes include all plants, animals, and fungi.

See Figure 3.2 Prokaryotes and Eukaryotes