Topic: Genetics
Aim: Describe some methods that can be used to develop organisms with desirable traits.
Directions: Read the text below. Use textual evidence to answer questions 1-14.
Genetic engineering involves biological and chemical methods to change the arrangement of a gene’s DNA. One
method of genetic engineering is gene splicing, or recombinant DNA which involves bringing together genetic material from
multiple organisms. Recombinant DNA can be made by inserting a gene from one organism into the DNA of a bacterium.
For example, the human gene that controls the production of insulin can be inserted into a bacterial cell. The bacterial cell
with this new recombinant DNA will begin producing insulin. Other uses include the production of growth hormone and
chemicals to treat cancer.
Genetic engineering can produce improvements in crop plants such as corn, wheat and rice. Scientists have recently
made genetically modified tomatoes with a gene that allows tomatoes to be picked green and transported great distances
before they ripen completely. This results in ripe, firm tomatoes available in local markets. However, the long-term effects of
consuming genetically modified plants are unknown.
Gene therapy involves adding or deleting segments of genes to correct or get rid of genetic disorders. Gene therapy
can be used to treat diseases such as cystic fibrosis, sickle cell anemia and muscular dystrophy. Viruses are often used in gene
therapy because they naturally bind to their hosts and introduce their genetic material. By removing the virus’ DNA, the virus
can be used as a vehicle to deliver beneficial DNA.
Cloning is when a new organism is made that has the exact same genes as the organism from which it was produced.
In 1996, cloning was revolutionized when scientists at the Roslin-Institute in Edinburgh, Scotland, successfully cloned a
sheep named Dolly. Cloning can occur through a process known as nuclear transplant. A nuclear transplant takes a nucleus
out of a somatic cell of the organism you desire to replicate. The nucleus is then placed inside an “empty” egg cell, or
enucleated egg, similar to the one to be cloned. The clone embryo is then placed inside the uterus of a surrogate mother so it
may fully develop into the cloned organism. Dolly was the first successfully cloned mammal. However, it took 276 attempts
before the experiment was successful. Dolly has since grown and reproduced several offspring of her own through normal
sexual means. Cloning could be used to bring back extinct species using DNA found in fossils, save endangered species, or
even clone a dead pet so you can enjoy their company again.
Sometimes we can genetically alter organisms without touching their DNA. For example, horse breeders will breed
their two “fastest” horses in order to get more horses that produce the same or faster results in racing. Selective breeding is
when we select two organisms with desired traits to serve as parents of the next generation.
Two forms of selective breeding are hybridization and inbreeding, which are opposites on the spectrum of genetic
diversity. Hybridization is when we cross two genetically different organisms, resulting in an organism that is said to have
the best traits from both parents. The offspring, or hybrid, are very different from either parent genetically because the alleles
from each parent are likely to be very different. This can be used in dog breeding. The production of designer dogs occurs
when, for example, breeders cross two purebred parents such as a such as Schnauzer and a poodle to produce a Schnoodle.
Inbreeding, on the other hand, occurs when two organisms that are very similar or have the same characteristics are
mated. Unfortunately, inbreeding increases the chances of recessive genetic disorders. This is because those disorders get
passed down in a population with no new genes being introduced. One example of inbreeding occurring naturally in the wild
involves the Cheetah. About 20,000 years ago, cheetahs almost became extinct due to climate change caused by the Ice Age.
Numbers have dwindled, and as a result, today’s cheetahs inherit from a small gene pool, so they have similar genes and lack
genetic diversity, something which is key to survival in an ever changing world. Male cheetahs often produce deformed
sperm cells, causing 75% of the baby cheetah population to not live past three months.
Questions:
1. Define genetic engineering. __________________________________________________________________________
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2. Identify what recombinant DNA consists of.
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3. How can recombinant DNA in bacteria be used to produce insulin?
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4. Identify other chemicals that can be produced using recombinant DNA. _______________________________________
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5. Describe the possible disadvantage of eating genetically modified plants.
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6. Describe gene therapy. _____________________________________________________________________________
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7. Identify some diseases that can be treated using gene therapy. ______________________________________________
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8. Describe the process of cloning. ______________________________________________________________________
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9. Identify the two cells used to produce Dolly. ____________________________________________________________
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10. Describe what was done with the two cells to produce a new cell. ____________________________________________
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11. Where was the new cell placed? _______________________________________________________________________
12. Describe what cloning can be used for. _________________________________________________________________
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13. Describe the process of selective breeding.
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14. Identify the two forms of selective breeding, ________________________________________________________________
15. Identify the type of selective breeding that creates offspring that are very different from either parent genetically.
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16. Identify the offspring of hybridization. _______________________________________
17. Identify the type of selective breeding that creates offspring that will be very similar to both parents. ___________________
18. Describe the disadvantage of inbreeding. _________________________________________________________________
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Review Questions:
1. Combining DNA from two different organisms results in
a. selective breeding
b. cloning
c. recombinant DNA
2. The deliberate changes made to an organism’s DNA is known as
a. inbreeding
b. genetic engineering
c. cloning
d. inbreeding
d. selective breeding
3. Cloning an individual usually produces organisms that
a. contain dangerous mutations
b. contain identical genes
c. are identical in appearance and behavior
d. produce enzymes different from the parent
4. Which process is most similar to the process of cloning?
a. Fertilization
b. Vegetative propagation
c. Meiosis
d. Gamete formation
5. Combining the desirable qualities of 2 different organisms into one is referred to as
a. genetic engineering
b. cloning
c. selective breeding
d. bacterial transformation
6. When humans first domesticated dogs, there was relatively little diversity in the species. Today, there are many variations
such as the German shepherd and the dalmation. This increase in diversity is most closely associated with
a. cloning
b. selective breeding
c. meiosis
d. recombinant DNA
7. White short-homed cattle and Black Angus cattle have been crossed to produce offspring with superior beef and rapid
growth qualities. This process of choosing organisms with the most desirable traits for mating is known as
a. cloning
b. inbreeding
c. genetic engineering
d. hybridization