New York State Chemistry RegentsNew York State Earth Science Regents

Heredity and Genetics
Living Environment Regents August 2010 Question 07 PDF Print E-mail
Friday, 27 May 2011 12:15

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

Direct harvesting is not a form of natural selection because it involves bias from the growers. This is usually done in agriculture to choose the species with specific characters desired for breeding.
Living Environment Regents August 2010 Question 09 PDF Print E-mail
Friday, 27 May 2011 12:20

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

Species A and a fungus is not capable of producing an offspring because they belong to different kingdoms of classification, thus they have different ways of reproduction. Plants usually form offspring by the use of pollens while fungi reproduce by the use of spores.
Living Environment Regents August 2010 Question 10 PDF Print E-mail
Friday, 27 May 2011 12:22

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

Though crossing over of chromosomes contribute to the formation of new genetic information with genes that are similar with the parents, the illustration is not enough to explain this statement.
Living Environment Regents August 2010 Question 15 PDF Print E-mail
Friday, 27 May 2011 12:42

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

A nerve cell is an example of a body cell. When body cells are mutated, the changes are not passed on to the next generation because only the mutated gametes or sex cells are involved in the formation of offspring.
Living Environment Regents August 2010 Question 23 PDF Print E-mail
Friday, 27 May 2011 13:18

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

Mutation is the rare change in the DNA of genes that ultimately creates genetic diversity. Since both parents exhibit the same trait, mutation unlikely explains the presence of the trait.
Living Environment Regents August 2010 Question 33 PDF Print E-mail
Friday, 27 May 2011 14:02

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

Replication occurs during cell division when each strand of the DNA becomes a template for the formation of complementary strands. This process is not used to produce glucose.
Living Environment Regents August 2010 Question 63 PDF Print E-mail
Friday, 27 May 2011 17:59
This procedure is called gel electrophoresis. It is used to separate DNA fragments. Through an electric current, the molecules of various sizes move through the porous sponge-like gel. The small molecules move through the gel faster than the bigger ones.
Living Environment Regents August 2010 Question 64 PDF Print E-mail
Friday, 27 May 2011 18:01

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

The smallest fragment will be the fastest to travel because of its small size, which allows them to easily pass through the pores of the gel.
Living Environment Regents August 2010 Question 65 PDF Print E-mail
Friday, 27 May 2011 18:08

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.

Living Environment Regents August 2010 Question 66 PDF Print E-mail
Friday, 27 May 2011 18:10
Gel electrophoresis is used in genetic fingerprinting, specifically in parental testing, forensic science, and the genetic diagnosis of evolutionary relationships. For example, DNA profiles of organisms can be compared to analyze possible evolutionary relationships. Those with similar DNA profiles could be closely related.

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