Alkaptonuria is a human autosomal recessive disorder caused by...

Question

Alkaptonuria is a human autosomal recessive disorder caused by mutation of the HAO gene that encodes the enzyme homogentisic acid oxidase. A map of the HAO gene region reveals four BamHI restriction sites (B1 to B4) in the wild-type allele and three BamHI restriction sites in the mutant allele. BamHI utilizes the restriction sequence 5′-GGATCC-3′. The BamHI restriction sequence identified as B3 is altered to 5′-GGAACC-3′ in the mutant allele. The mutation results in a Ser-to-Thr missense mutation. Restriction maps of the two alleles are shown below, and the binding sites of two molecular probes (probe A and probe B) are identified.
Restriction maps of wild-type and mutant alleles with BamHI sites and molecular probes A and B indicated.

Restriction maps of wild-type and mutant alleles with BamHI sites and molecular probes A and B indicated.

DNA samples taken from a mother (M), father (F), and two children (C1 and C2) are analyzed by Southern blotting of BamHI-digested DNA. The gel electrophoresis results are illustrated.
Southern blot results showing DNA bands for mother (M), father (F), and children (C1, C2) with sizes in kilobases.

Southern blot results showing DNA bands for mother (M), father (F), and children (C1, C2) with sizes in kilobases.

Using A to represent the wild-type allele and a for the mutant allele, identify the genotype of each family member. Identify any family member who is alkaptonuric.

Restriction maps of wild-type and mutant alleles with BamHI sites and molecular probes A and B indicated.

DNA samples taken from a mother (M), father (F), and two children (C1 and C2) are analyzed by Southern blotting of BamHI-digested DNA. The gel electrophoresis results are illustrated.

Southern blot results showing DNA bands for mother (M), father (F), and children (C1, C2) with sizes in kilobases.

Using A to represent the wild-type allele and a for the mutant allele, identify the genotype of each family member. Identify any family member who is alkaptonuric.

Accepted Answer

Hey, everyone. Let's take a look at this question together. Al CAPP auria is a genetic disorder caused by a mutated gene that affects the homogenic acid oxidase enzyme. The mutant gene has a different bam H one restriction site than the normal gene resulting in a serene torian mis sense mutation. If a heterozygous mother or the mutant gene and a homozygous father or the mutant gene have Children, what is the expected genotypic ratio of the offspring? Is it answer choice? A 1 to 2 to one answer, choice B 1 to 1 answer choice C 3 to 1 or answer choice D 2 to 1. Let's work this problem out together to try to figure out which of the following answer choices is the expected genotypic ratio of the offspring. So we can see that we have a heterozygous mother with that heterozygous genotype. And we have a homozygous father that is homozygous recessive. And we are trying to determine an expected genotypic ratio, which means that we have to set up a punt square. So here we have our puit square where we have our mother on the top and the father on the left. So we can go ahead and do our puit square cross to determine the genotypic ratio of their offspring. And we are able to determine that 50% of their offspring will have that heterozygous genotype and 50% of their offspring will be homozygous recessive, which means that we have a 1 to 1 ratio, meaning that we have a 1 to 1 ratio of heterozygous two homozygous recessive. Since we have 50% percent of the offspring heterozygous and 50% of the offspring are homozygous recessive. So answer choice B is the correct answer based on our puna square cross of our heterozygous mother and our homozygous recessive father where we can see that we have 50% are heterozygous and 50% are homozygous recessive. Giving us that 1 to 1 ratio. Making answer choice B the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

Key Concepts

Autosomal Recessive Inheritance

Restriction Enzymes and Restriction Mapping

Missense Mutation

Watch next