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NYS Living Environment Regents June 2010
Living Environment Regents June 2010 Question 75 PDF Print E-mail
NYS Living Environment Regents June 2010

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Correct answer: (1) cut the DNA at a specific location

This enzyme that cuts the DNA at specific location is called a restriction enzyme. It is one of the tools used in recombinant DNA technology or genetic engineering. In this technology, restriction enzymes are used to cut the foreign DNA and the resulting restriction fragments are double-stranded DNA fragments containing single-stranded ends, called sticky ends. These sticky ends can be used to join DNA pieces originating from different sources.

Incorrect answers:

(2) move the DNA to a different organism

The process of moving the DNA or a portion of it (containing a gene of interest) into a different organism is called recombinant DNA technology. Recombinant DNA pertains to the combination of DNA from two sources. Enzymes are substances that increase or decrease the rate of reaction. Thus, enzymes cannot serve as transporters of DNA from one source to another.

(3) copy the DNA for protein synthesis

During replication or the process of copying the DNA, the DNA is not cut into pieces. Instead, two strands of the DNA are opened up by the help of specialized proteins

(4) alter the DNA sequence in the segment

Mutation or change in the DNA sequence cannot be caused by enzymes. Mutation may be brought about by chemicals or radiation.
 
Living Environment Regents June 2010 Question 71 PDF Print E-mail
NYS Living Environment Regents June 2010
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DNA analyses, such as gel electrophoresis, are more accurate because they supply information at the molecular level, which is more specific compared to merely inspecting the appearance of stem cross sections. Stem cross sections of various species may look the same but they may not be genetically associated. It is important to use genetic analyses because it is based on the DNA, which is unique to an organism, and similar only with the related organisms.
 
Living Environment Regents June 2010 Question 70 PDF Print E-mail
NYS Living Environment Regents June 2010
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Correct answer: (2) separation of DNA fragments on the basis of size

Gel electrophoresis is a laboratory technique used to separate DNA fragments according to size as they move through the gel matrix using electricity. The DNA fragments are attracted towards the other end of the matrix, and the smaller molecules move faster than the large ones. This technique is used in DNA profiling to identify possible genetic relationships of organisms.

Incorrect answers:

(1) Synthesis of new DNA strands from subunits

Prior to electrophoresis, DNA fragments could be amplified using polymerase chain reaction (PCR). It is important to make copies of the DNA to help the researcher in other different molecular biology laboratory techniques.

(3) production of genetically engineered DNA molecules

Gel electrophoresis is only a molecular biology technique that may be used to know the presence of genes to be used for genetic engineering. It is not the process used to produce genetically engineered DNA. Instead, genetic engineering can be carried out through recombinant DNA technology.

(4) removal of defective genes from DNA

Gel electrophoresis is a process of classifying DNA molecules according to their sizes. It is not used for deletion of unwanted genes from the DNA. Unwanted genes can be "turned off" using genetic engineering techniques.

 
Living Environment Regents June 2010 Question 69 PDF Print E-mail
NYS Living Environment Regents June 2010
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Diagram 3 is an example of a simplified cladogram. A cladogram is dichotomous phylogenetic tree that branches repeatedly, suggesting a classification of organisms based on the time sequence in which evolutionary branches. Each branch point is defined by synapomorphies or shared derived characters unique to the lineage that arises at that point. In Diagram 3, species A and B have shared characters which could be represented by the bands in Diagram 2 that appear on the same spot and with the similar thickness.

On the other hand, the ancestor of species A and B share a common character with species C but since it quite apart from the characteristics of  A and B, only few bands are common in the three species.
 
Living Environment Regents June 2010 Question 68 PDF Print E-mail
NYS Living Environment Regents June 2010
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Diagram 1 cannot be used to know on confirm the evolutionary relationships of organisms. By merely looking at the stem cross sections, they may look the same. Just like in humans, some people may look the same but in truth they are not genetically related to each other. Thus, scientists are using genetic techniques such as gel electrophoresis which produces DNA profiles of organisms. Diagram 2 is an example of a DNA profile.

 
Living Environment Regents June 2010 Question 55 PDF Print E-mail
NYS Living Environment Regents June 2010
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Type of gamete: ZW

In birds and some fishes, the variable that determines sex is the sex chromosome present in the ovum, not in the sperm. The males are ZZ and females are ZW. The female gamete ZW determines the sex of the offspring because it is composed of two different types of chromosomes.
 
Living Environment Regents June 2010 Question 34 PDF Print E-mail
NYS Living Environment Regents June 2010
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Correct answer: (1) deletion-substitution-insertion

Mutations are changes in the genetic makeup of a cell.Point mutation is a type of mutation caused by chemical changes that occurs in a single base nucleotide in a single gene. This type of mutation could be a deletion, insertion, or substitution of a nucleotide. Mutation A illustrates a deletion, wherein one nucleotide is lost. The normal sequence has 9 nucleotides, while the resulting sequence after mutation only contains 8 nucleotides.

Mutation B represents substitution, wherein one nucleotide is replaced with another nucleotide. The first nucleotide in the normal sequence is cytosine (C), and then it was substituted with guanine (G) after mutation occurred.

Mutation C shows an example of insertion because there was an additional nucleotide in the mutated sequence. The normal sequence contains only 9 nucleotides, while the mutated sequence already has 10 nucleotides.

Among these three types, deletion and insertion could be harmful to the organism.

Incorrect answers:

(2) insertion-substitution-deletion

Mutation A could not be considered as insertion because there is no additional nucleotide in the sequence, while mutation C is not an example of deletion because no nucleotide was added in the sequence.

(3) insertion-deletion-substitution

Mutation A is not an example of insertion because there was no addition of a nucleotide. Mutation B is not considered as deletion because the mutated sequence has the same number of nucleotides with the normal sequence. An additional nucleotide was exhibited in mutation C; thus it is insertion, not substitution.

(4) deletion-insertion-substitution

There is no additional nucleotide in mutation B that is why it is not considered as an insertion. There is an additional nucleotide in mutation C, thus it is insertion, not substitution.
 
Living Environment Regents June 2010 Question 21 PDF Print E-mail
NYS Living Environment Regents June 2010
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Correct answer: (1) genetically inherited from parents

If the young birds have been isolated from the other members of the species but still exhibit the same behavior with their kind, then that characteristic must be due to their genes. Behavior is controlled by complex traits and it is species-specific.

Incorrect answers:

(2) learned by watching members of their species

This cannot be true because the young birds have been isolated from their kind, thus, they cannot copy the behavior of the species in the original location.

(3) a disadvantage to the survival of the species

Since the behavior which has been tried and tested is still used, then the species would have high chance of continuing its kind. But if the species starts to change its behavior apart from its kind, then evolution could occur, and new species could arise making the old species extinct.

(4) a direct result of the type of food the bird eats

Food has no effect on the nest-building behavior of the birds. Behaviors are regulated by complex traits not by the food that the birds eat.

 
Living Environment Regents June 2010 Question 16 PDF Print E-mail
NYS Living Environment Regents June 2010
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Correct answer: (3) gene expression may be influenced by factors that switch genes on and off

Identical twins have exactly the same set of genetic information. However, they have different phenotypes or the physical and physiological expression of genes. Thus, identical twins may have differences when exposed to factors that may affect the expression of genes such as the environment.

Incorrect answers:

(1) each twin receives different chromosomes

Since identical twins have the same genetic information, then it also means that they have the same set of chromosomes.

(2) one twin may only have genes from the father

All offsprings have combined genes from the parents because during fertilization, haploid games are united to form a diploid offspring.

(4) gene mutation may have occurred before the zygote divided

Mutation is the rare change in the DNA of genes that ultimately creates genetic diversity. Mutation can be caused by exposure to chemicals or radiation. It is almost impossible for mutation to occur before the zygote divides because the zygote is very small and is inside the female reproductive system.
 
Living Environment Regents June 2010 Question 12 PDF Print E-mail
NYS Living Environment Regents June 2010
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Correct Answer: (4) genetic engineering

The illustration shows the process of genetic engineering or recombinant DNA technology. The first step in this technique is called DNA extraction. During this process, the DNA from the desired organism in extracted then treated with restriction enzymes which cuts the DNA into smaller portions with defined ends to so that it can be cloned into bacterial vectors. These vectors are transformed into bacterial cells and thousands of copies are produced. After gene cloning, the gene of interest will be linked to other DNA components that will regulate its expression in the cell. Then the gene will be inserted to the bacterial cell through the use of gene gun or Agrobacterium-mediated transformation.

Incorrect Answer:

(1) chromatography

Chromatography is a laboratory technique used to separate mixtures. The sample of the mixture is dissolved in a mobile phase. The mobile phase is then forced through a steady, immiscible stationary phase. The phases are selected so that the components of the sample have differing solubilities in each phase. The component that is soluble in the stationary phase will be slower in moving through it than the component that is not very soluble in the stationary phase but very soluble in the mobile phase. Since they have different rates of movement due to solubility, the components of the sample will be separated from each other as they move through the stationary phase. There are no DNA, plasmid vector, and bacterial cell involved in this process, thus the illustration does not pertain to chromatography.

(2) gel electrophoresis

Gel electrophoresis refers to the process of separating molecules on their differential mobility in an electric field. The smaller molecules move through the gel faster than the larger molecules. In genetic engineering, it is used to separate DNA fragments. Therefore, the illustration does not explain this process.

(3) direct harvesting

Direct harvesting is a technique used in molecular biology usually in collecting samples from the internal parts of the body for analysis. For instance, bone marrow sample is collected through direct harvesting for cancer studies.
 
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