The concept of genomic imprinting is important in human genetics. In genomic imprinting, a certain region of DNA is only expressed by one of the two chromosomes that make up a typical homologous pair. In healthy individuals, genomic imprinting results in the silencing of genes in a certain section of the maternal chromosome 15. The DNA in this part of the chromosome is "turned off" by the addition of methyl groups to the DNA molecule. Healthy people will thus only have expression of this section of chromosome 15 from paternally-derived DNA.

The two classic human diseases that illustrate defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of paternal chromosome 15 that is usually expressed is disrupted, such as by a chromosomal deletion. In Angelman Syndrome, maternal genes in this section are deleted, while paternal genes are silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, while Angelman Syndrome is linked to maternal inheritance.

Figure 1 shows the chromosome 15 homologous pair for a child with Prader-Willi Syndrome. The parental chromosomes are also shown. The genes on the mother’s chromosomes are silenced normally, as represented by the black boxes. At once, there is also a chromosomal deletion on one of the paternal chromosomes. The result is that the child does not have any genes expressed that are normally found on that region of this chromosome.

A scientist discovers another genetic disease that has similar symptoms to Prader-Willi Syndrome. He discovers that this disease is recessive, and caused not by changes to chromosome 15, but by a point mutation on chromosome 3. He calculates the recessive allele frequency in a population to be .

Assuming the that normal allele, , and recessive allele, , are the only two alleles in this population, what is the percentage of the population that has the disease?

A rare recessive mutation causes rabbits that are normally white to be pink. If one in a hundred rabbits is pink, what is the frequency of the pink allele?

The concept of genomic imprinting is important in human genetics. In genomic imprinting, a certain region of DNA is only expressed by one of the two chromosomes that make up a typical homologous pair. In healthy individuals, genomic imprinting results in the silencing of genes in a certain section of the maternal chromosome 15. The DNA in this part of the chromosome is "turned off" by the addition of methyl groups to the DNA molecule. Healthy people will thus only have expression of this section of chromosome 15 from paternally-derived DNA.

The two classic human diseases that illustrate defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of paternal chromosome 15 that is usually expressed is disrupted, such as by a chromosomal deletion. In Angelman Syndrome, maternal genes in this section are deleted, while paternal genes are silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, while Angelman Syndrome is linked to maternal inheritance.

Figure 1 shows the chromosome 15 homologous pair for a child with Prader-Willi Syndrome. The parental chromosomes are also shown. The genes on the mother’s chromosomes are silenced normally, as represented by the black boxes. At once, there is also a chromosomal deletion on one of the paternal chromosomes. The result is that the child does not have any genes expressed that are normally found on that region of this chromosome.

A child is diagnosed with a genetic disease, and two years later his parents have another child. The second child also inherited the gene mutation, but does not express the disease. Which of the following is reduced in the second child?

Researchers are studying a disease that causes neurological deficits in humans. They have identified the disorder as autosomal dominant, but notice that about 20% of people with the dominant disease allele do not express any of the associated neurological impairment. What genetics term explains this phenomenon?

If forty percent of a Hardy-Weinberg population is phenotypic for an autosomal recessive trait, approximately what percent of the population will be heterozygous?

The Hardy-Weinberg principle is a tool used to predict the allele and disease frequencies in a given population. If we know the proportion of either the recessive or dominant allele, we can calculate the proportion of population with homozygous dominant, heterozygous, and recessive genotypes using Hardy-Weinberg principles. For example, let’s assume the frequency of the dominant allele for a particular gene is  and that for recessive allele is . Hardy-Weinberg principle states the following:

This principle also allows us to calculate the proportion of genotypes by squaring both sides of the above equation.

Where  is the proportion of homozygous dominant,  is proportion of heterozygous individuals, and  is proportion of recessive individuals. These equations can only be used for populations in Hardy-Weinberg equilibrium.

A researcher is analyzing a group of indigenous people on a remote island. He observes that a rare, autosomal recessive allele is found in 25% of the population. How many people on this island are unaffected by this disease? There are 100 people living on this island.

The Hardy-Weinberg principle is a tool used to predict the allele and disease frequencies in a given population. If we know the proportion of either the recessive or dominant allele, we can calculate the proportion of population with homozygous dominant, heterozygous, and recessive genotypes using Hardy-Weinberg principles. For example, let’s assume the frequency of the dominant allele for a particular gene is  and that for recessive allele is . Hardy-Weinberg principle states the following:

This principle also allows us to calculate the proportion of genotypes by squaring both sides of the above equation.

Where  is the proportion of homozygous dominant,  is proportion of heterozygous individuals, and  is proportion of recessive individuals. These equations can only be used for populations in Hardy-Weinberg equilibrium.

Which of the following is not an assumption of Hardy-Weinberg principle?

The Hardy-Weinberg principle is a tool used to predict the allele and disease frequencies in a given population. If we know the proportion of either the recessive or dominant allele, we can calculate the proportion of population with homozygous dominant, heterozygous, and recessive genotypes using Hardy-Weinberg principles. For example, let’s assume the frequency of the dominant allele for a particular gene is  and that for recessive allele is . Hardy-Weinberg principle states the following:

This principle also allows us to calculate the proportion of genotypes by squaring both sides of the above equation.

Where  is the proportion of homozygous dominant,  is proportion of heterozygous individuals, and  is proportion of recessive individuals. These equations can only be used for populations in Hardy-Weinberg equilibrium.

Which of the following is true regarding allele and disease frequency?

The Hardy-Weinberg principle is a tool used to predict the allele and disease frequencies in a given population. If we know the proportion of either the recessive or dominant allele, we can calculate the proportion of population with homozygous dominant, heterozygous, and recessive genotypes using Hardy-Weinberg principles. For example, let’s assume the frequency of the dominant allele for a particular gene is  and that for recessive allele is . Hardy-Weinberg principle states the following:

This principle also allows us to calculate the proportion of genotypes by squaring both sides of the above equation.

Where  is the proportion of homozygous dominant,  is proportion of heterozygous individuals, and  is proportion of recessive individuals. These equations can only be used for populations in Hardy-Weinberg equilibrium.

In a patient, it is observed that a gene on an autosomal chromosome is silenced whereas its homologous counterpart is active. The activated gene codes for a protein that causes a particular type of disease. It is found that 2 percent of the population have this activated gene. What is the incidence of this rare disease in the population?

The concept of genomic imprinting is important in human genetics. In genomic imprinting, a certain region of DNA is only expressed by one of the two chromosomes that make up a typical homologous pair. In healthy individuals, genomic imprinting results in the silencing of genes in a certain section of the maternal chromosome 15. The DNA in this part of the chromosome is "turned off" by the addition of methyl groups to the DNA molecule. Healthy people will thus only have expression of this section of chromosome 15 from paternally-derived DNA.

The two classic human diseases that illustrate defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of paternal chromosome 15 that is usually expressed is disrupted, such as by a chromosomal deletion. In Angelman Syndrome, maternal genes in this section are deleted, while paternal genes are silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, while Angelman Syndrome is linked to maternal inheritance.

Figure 1 shows the chromosome 15 homologous pair for a child with Prader-Willi Syndrome. The parental chromosomes are also shown. The genes on the mother’s chromosomes are silenced normally, as represented by the black boxes. At once, there is also a chromosomal deletion on one of the paternal chromosomes. The result is that the child does not have any genes expressed that are normally found on that region of this chromosome.

A scientist discovers another genetic disease that has similar symptoms to Prader-Willi Syndrome. He discovers that this disease is recessive, and caused not by changes to chromosome 15, but by a point mutation on chromosome 3. He calculates that  of the population is healthy. Assuming the normal allele, , and recessive allele, , are the only two alleles in this population, what is the allele frequency of ?