Use These Notes to Study for Your C13 &14 Test Chapters 13 & 14 Test Use These Notes to Study for Your C13 &14 Test

Mutations are useful in selective breeding because they are occasionally beneficial. Breeders induce mutations in organisms to increase diversity in populations. The crossing of buffalo and cattle to produce beefalo is an example of hybridization.

Luther Burbank produced over 800 varieties of plants by selective breeding. http://www.joytoyou.com

Horse, dog, and cat breeds have all been produced by selective breeding. Selective breeding produces desired traits in offspring. Allowing dogs to mate only once a year is not an example of selective breeding. Inbreeding is most likely to bring together two recessive alleles for a genetic defect. The ultimate source of genetic variability is mutation.

Polyploidy instantly results in a new plant species because it changes a species’ number of chromosomes. One function of gel electrophoresis is to separate DNA fragments. The process of making changes in the DNA code of a living organism is called genetic engineering. On an electrophoresis gel, band B is closer to the positive end of the gel than is band A. The DNA fragments in band B must then be smaller than those in band A. Knowing the sequence of an organism’s DNA allows researchers to study specific genes.

The diagram above shows a restriction enzyme producing a DNA fragment

Genetic engineering involves reading a DNA sequence, editing a DNA sequence, and reinserting DNA into living organisms. Suppose a restriction enzyme recognizes the six-base sequence in a double strand of DNA. CAATTG GTTAAC If the cut creates two sticky ends that are four bases long, what will one of the exposed sequences (sticky ends) be? AATT A DNA molecule produced by combining DNA from different sources is known as recombinant DNA.

If two DNA samples showed an identical pattern and thickness of bands produced by gel electrophoresis, the samples contained the same amount of DNA, the same DNA molecules, and DNA fragments of the same size. During transformation a cell takes in DNA from outside the cell. Scientists can transform plant cells by using the bacterium Agrobacterium tumefaciens, removing the plant cell walls and then mixing the cells with DNA, or injecting DNA into the plant cells. A recombinant plasmid gets inside a bacterial cell by transformation.

In order to produce recombinant DNA, it is essential to cut out a piece of DNA from a DNA molecule, splice a piece of DNA into DNA from another organism, or use a restriction enzyme to cut DNA into fragments. Plasmid is a form of bacterial DNA. A gene that makes it possible to distinguish bacteria that carry a plasmid (and a foreign DNA) from those that don’t is called a genetic marker. A gene for antibiotic resistance is often used as a genetic marker. The transformation of a plant cell is successful if the foreign DNA is integrated into one of the cell’s chromosomes.

A defective gene in a cell being replaced with a normal gene is an example of successful transformation. Suppose a bacterial culture were mixed with recombinant plasmids containing a gene for resistance to penicillin. The bacterial culture was then treated with penicillin. Those bacteria that contain the plasmid will survive. The gene for antibiotic resistance is expressed in the bacteria that survive. Those bacteria that are successfully transformed will survive. Genetic engineering is the technique scientists use to make transgenic organisms. Increasing the food supply has been an advantage of producing transgenic plants. The Scottish scientist Ian Wilmut cloned a sheep.