An individual who is homozygous has

The expected genotype frequencies. The number of heterozygous individuals that you would predict to be in this population. Answer: That would be 0. The expected phenotype frequencies.

Conditions happen to be really good this year for breeding and next year there are 1, young "potential" Biology instructors. Assuming that all of the Hardy-Weinberg conditions are met, how many of these would you expect to be red-sided and how many tan-sided?

White coloring is caused by the double recessive genotype, "aa". Calculate allelic and genotypic frequencies for this population. The square root of 0. Now that we know the frequency of each allele, we can calculate the frequency of the remaining genotypes in the population AA and Aa individuals. If you add up all these genotype frequencies, they should equal 1. After graduation, you and 19 of your closest friends lets say 10 males and 10 females charter a plane to go on a round-the-world tour.

Unfortunately, you all crash land safely on a deserted island. No one finds you and you start a new population totally isolated from the rest of the world.

Two of your friends carry i. Assuming that the frequency of this allele does not change as the population grows, what will be the incidence of cystic fibrosis on your island? Answer: There are 40 total alleles in the 20 people of which 2 alleles are for cystic fibrous. That represents p. You sample 1, individuals from a large population for the MN blood group, which can easily be measured since co-dominance is involved i.

Supposing the matings are random, the frequencies of the matings. Answer: This is a little harder to figure out. Try setting up a "Punnett square" type arrangement using the 3 genotypes and multiplying the numbers in a manner something like this: MM 0. Thus, three of the possibilities must be doubled.

Cystic fibrosis is a recessive condition that affects about 1 in 2, babies in the Caucasian population of the United States. Please calculate the following. The frequency of the recessive allele in the population. Therefore, q is the square root, or 0. Why is it important for you to know about Punnett squares? The answer is that they can be used as predictive tools when considering having children. Let us assume, for instance, that both you and your mate are carriers for a particularly unpleasant genetically inherited disease such as cystic fibrosis.

Of course, you are worried about whether your children will be healthy and normal. For this example, let us define "A" as being the dominant normal allele and "a" as the recessive abnormal one that is responsible for cystic fibrosis.

As carriers, you and your mate are both heterozygous Aa. This disease only afflicts those who are homozygous recessive aa. If a carrier Aa for such a recessive disease mates with someone who has it aa , the likelihood of their children also inheriting the condition is far greater as shown below.

On average, half of the children will be heterozygous Aa and, therefore, carriers. The remaining half will inherit 2 recessive alleles aa and develop the disease. It is likely that every one of us is a carrier for a large number of recessive alleles.

Some of these alleles can cause life-threatening defects if they are inherited from both parents. In addition to cystic fibrosis, albinism, and beta-thalassemia are recessive disorders. Some disorders are caused by dominant alleles for genes. Inheriting just one copy of such a dominant allele will cause the disorder. This is the case with Huntington disease, achondroplastic dwarfism, and polydactyly. People who are heterozygous Aa are not healthy carriers.

They inherit two different sex chromosomes: X and Y. You may have heard of sex-linked diseases, like Duchenne muscular dystrophy. These display a different inheritance pattern than standard recessive or dominant diseases inherited through the other chromosomes called autosomes.

For some disease genes, it is possible that being a heterozygote gives a person certain advantages. When two people have a child, there are several possibilities:. The study of genetics is complex. Alleles are different forms or variations of a gene. They help determine the traits that are inherited from our parents, such as eye color, skin pigmentation, blood type, height, and more. Heterozygous is when different forms of a specific gene are inherited from each parent.

Homozygous is when a gene inherited from each parent is identical. Basically, heterozygous means different while homozygous means the same. Genotype is a term used to define an individual's entire collection of genes.

Humans share mostly similar DNA, but there are variations in certain sequences. These varieties are what separate us from one another. Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life.

Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management. Scientific World Journal. Mahalingam S, Levy LM.

Genetics of Huntington disease. American Journal of Neuroradiology. The importance of genetic diagnosis for Duchenne muscular dystrophy. J Med Genet. National Human Genome Research Institute. Genetics in Medicine 7th ed. Philadelphia, PA: Sauders Elsevier; Your Privacy Rights. To change or withdraw your consent choices for VerywellHealth. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.

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I Accept Show Purposes. Table of Contents View All. Table of Contents. Gene Variation. Disease Mutations. Genetic Diseases. Sex Chromosomes. Heterozygote Advantage.

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