Genetic Selection: Definition, Pros & Cons

Genetic Selection: Definition, Pros & Cons
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  • 0:00 Genetic Selection Definition
  • 3:05 Artificial Selection In Humans
  • 4:05 Genetic Selection And…
  • 5:13 Gender Selection
  • 5:34 Designer Babies
  • 6:20 Lesson Summary
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Lesson Transcript
Instructor: Erika Steele

Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.

When it comes to the genetic traits of a population, 'selection' is the process that chooses those traits. Artificial genetic selection is controversial, especially when it comes to human beings. This lesson defines genetic selection and discusses the pros and cons of artificial genetic selection.

Genetic Selection Definition

You may have noticed that squirrels in one location may be grey while in another location they are brown, even though they are the same species. Many male birds tend to be more brightly colored than female birds, despite the fact that bright colors make it hard to hide from predators. All domestic dogs are the same species even though there is a huge variation in the way they look. Each of these is an example of genetic selection.

All species of living things have physical traits that are inherent to that species. Genetic selection is the process by which certain traits become more prevalent in a species than other traits. These traits seen in an organism are due to the genes found on their chromosomes. The genes code for the traits that we are able to observe.

Figure 1: Alleles for genes are inherited and come in various forms.
Alleles come in multiple forms

Genes have more than one version or allele. We inherit one allele for every gene from each of our parents as shown in Figure 1 here. Some alleles are seen more frequently in a population because there are factors that select those genes.

Figure 2: There are two types of selection: 1) Natural and 2) Artificial.
Types of Selection

In natural selection, natural forces determine the traits seen in an organism. A variation or allele of a trait makes some individuals more suited to survive in the environment. Mating behavior that leads to a sexual preference for a trait is also natural selection.

Figure 3: The fur color of the pocket mouse is influenced by the color of the terrain.
Natural selection

As shown in Figure 3 here, if you are a mouse and you can blend in with the environment you are likely to live long enough to pass on your genes for coat color to baby mice. Your friend who could not blend in gets eaten and does not pass on the genes for their coat color. Over time, the mice in dark areas will have dark fur and the mice in light areas will have light fur. Natural selection by the environment eliminates the weakest individuals from the gene pool. If the mice did not have a gene for coat color that allowed them to hide from predators, that species of mouse would be eliminated from the environment.

Figure 3: Some traits are prevalent in a population due to sexual preferences.
Sexual selection

Natural selection also occurs when a species has a preference for certain traits for sexual reasons. Male peafowl (peacocks) have elaborate tail feathers because female peacocks are attracted to really nice tails. This is called sexual selection since traits are being selected for sexual reasons.

Figure 4: Apple variety and variety in traits seen in dogs are a result of artificial selection.
Artificial Selection

Artificial selection involves human interference in natural selection. Humans have been selecting various traits in other organisms for thousands of years. It is how we have developed a huge variety in the colors and flavors of apples. It's also the reason we have little tiny dogs and extremely large dogs. We select traits in plants and animals to use them to our advantage. Artificial selection in plants and animals is not seen as being as controversial, as it is with humans. Genetic selection in humans raises ethical questions, such as who gets to live and who is asked for permission to make certain selections.

Artificial Selection in Humans

Figure 4: Human genetic selection involves taking DNA samples from an embryo and screening it for disease. Parents are then given the option to continue or terminate the pregnancy.
Genetic Selection of Embryos

Human genetic selection (screening procedures) are done on embryos that have not yet been implanted or on a fetus in the first or second trimester of pregnancy. Fetuses are often screened for the presence of genetic diseases, such as Down's Syndrome, Sickle Cell Anemia, Cystic Fibrosis, and Tay-Sachs disease, especially in cases where the mother is at risk.

Genetic screening of embryos is done before implantation in the uterus. Samples of the embryo's DNA are taken and then screened for genetic disease. The DNA sample can be taken before implantation (as shown in the figure here) or after the embryo has been implanted in the uterus. After genetic testing, the parents are given the chance to make a decision about implanting the embryo, continuing with a pregnancy, or terminating it. Because a decision as to whether or not a human pregnancy is to continue, genetic screening in humans is seen as controversial.

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