Children B and D have similar DNA profiles. All the bands are located at the same sites, meaning the smallest fragments of both samples have the same molecular sizes. This goes the same with the other bands.

Correct answer: (2) smallest fragment of DNA that traveled the fastest

Band X, which is the band farthest from the wells, represents the smallest fragment that passed through the sponge-like matrix of the gel. It is easier for the smaller molecules to move through the pores of the gel because of their sizes.

Incorrect answers:

(1) largest fragment of DNA that traveled the fastest

It will take a longer time for the largest molecules to travel through the gel because of their sizes.

(3) largest fragment of the DNA that traveled the slowest

Though it is true that the larger fragments move the slowest, it is not true that Band X represents the largest fragment. If the large fragment moves slowly, then it would be the nearest band from the well where the DNA sample was placed.

(4) smallest fragment of DNA that traveled the slowest

Correct answer: (3) genetic engineering-insulin

The diagram illustrates the process of producing insulin through the recombinant DNA technology or genetic engineering. First, a plastid is taken from a bacterial cell. Using a special enzyme, the plastid is opened. DNA from human coding for the synthesis of insulin is inserted into the plasmid. The plasmid and the inserted DNA are closed using another enzyme. The recombined plasmid is then inserted to Escherichia coli, a common bacterium. E. coli divides into new cells with the same genetic makeup as the original. These newly formed cells now produce insulin.

Incorrect answer:

(1) selective-breeding-growth hormone

Selective breeding is a method used in choosing individuals for breeding. It cannot be used to produce growth hormones in bacteria.

(2) cloning-antibiotics

Cloning is the process of producing populations with the same genetic makeup. This is not used to make antibiotics. Mutation is used in the production of antibiotics.

(4) replicating-glucose

Correct answer: (3) selective breeding

It is possible that the Seattle Slew was bred to be fast by selective breeding. Since both parents carry the genes for being fast, then there is high probability that the offspring also exhibit the same trait.

Incorrect answers:

(1) environmental selection

Natural or environmental selection refers to the differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. This kind of selection is usually random, driven by survival of species.  This could lead to evolution or speciation; however, both would take a long time to be evident.

(2) alteration of DNA molecules

The alteration of DNA molecules is also known as genetic engineering, usually done by inserting one or more desirable traits into an organism through the recombinant DNA technology. The genes that confer the desired trait usually come from a different species that cannot interbreed with the transgenic organism. Seattle Slew is not genetically altered to be fast because both parents already exhibit the desired trait.

(4) a sudden mutation

Correct answer: (2) the gametes of either parent

Mutation can only cause a change in the next generations if it occurs in the sex cells or gametes of either parent and alters their genetic information. Mutation that occurs in the body cells, such as skin cells and nerve cells, will not affect the offspring because these cells would not be involved in the fertilization of new offsprings.

Incorrect answers:

(1) the skin cells of the mother

Mutations that occurr in the skin cells will not affect the DNA of the offspring because body cells are not involved in fertilization of the formation of offsprings.

(3) all the body cells of both parents

The mutation of body cells will not cause an alteration in the DNA because they do not contribute during fertilization. Only mutated sex cells or gametes may cause a transformation in the genetic information of the offspring.

(4) only the nerve cells of the father

Correct answer: (4) the origin of new combinations of traits in offspring

The X-shaped region (in the second stage of the illustration) is called the chiasma (plural, chiasmata) which is a physical manifestation of a process called chromosomal cross over. Through this process that is a characteristic of meiosis, genetic rearrangement occurs.

Incorrect answers:

(1) why some offspring are genetically identical to their parents

Based on the illustration, the resulting chromosomes (Bb and Bb) are different from the original ones (BB and bb). Thus, genetic rearrangement occurred through the process of crossing over of chromosome, leading to the formation of a new set of chromosomes, different of the parents.

(2) the process of differentiation in offspring

Differentiation is the structural and functional divergence of cells as they become specialized during a multicellular organism's development. This occurs in the later part of development of body cells. The diagram illustrates what occurs in the gametes or sex cells.

(3) why some offspring physically resemble their parents

Correct answer: (3) insert the gene for the protein from species B into a chromosome in species A

Genetic engineering is the processes of altering the genetic makeup of an organism through recombinant DNA technology which involves laboratory tools and enzymes that cut out, insert, and alter species of DNA that contain one or more genes of interest.

Incorrect answers:

(1) mutate fungal DNA and introduce the mutated DNA into species B using a virus

Mutagenesis can be done to improve traits. However, a virus cannot be used to introduce the mutated DNA. Genes can be inserted by particle bombardment using a gene gun, or through the use of Agrobacterium tumefaciens, which is a bacterium, not a virus. The statement is also incorrect because it is not species B that needs transformation because it already produces the protein that provides resistance to the fungal infection.

(2) add DNA from species B into the soil around species A

Adding DNA into the soil is useless because it does not function like nutrients that can sip through the soil then to the plant. The gene from the DNA that code for resistance must be inserted directly to the DNA of species A through particle bombardment or Agrobacterium tumefaciens-mediated transformation.

(4) cross species A and a fungus to stimulate the synthesis of this protein

Correct answer: (3) natural selection

Natural selection refers to the differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Natural selection can bring about adaptive evolution which is a blend of chance and sorting-chance in the origin of new genetic variation and sexual recombination, and sorting in the workings of selection as it favors the propagation of some chance variations over others. From the range of variations available to it, natural selection increases the frequencies of certain genotypes and fits organisms in their environments.

Incorrect answers:

(1) ecosystem stability

Ecosystem stability refers to the unity of organisms on Earth. Unity and diversity are the two main factors that characterize life on Earth.

(2) homeostasis

Homeostasis refers to the steady-state physiological condition of the body.

(4) direct harvesting