A hereditary disease is inherited as an autosomal recessive trait1. The wild-type allele of the disease gene produces a mature mRNA that is 1250 nucleotides (nt) long. Molecular analysis shows that the mature mRNA consists of four exons that measure 400 nt (exon 1), 320 nt (exon 2), 230 nt (exon 3), and 300 nt (exon 4). A mother and father with two healthy children and two children with the disease have northern blot analysis performed in a medical genetics laboratory. The results of the northern blot for each family member are shown here. Identify the genotype of each family member, using the sizes of mRNAs to indicate each allele. (For example, a person who is homozygous wild type is indicated as '1250/1250.')

What advantages do cDNA libraries provide over genomic DNA libraries? Describe cloning applications where the use of a genomic library is necessary to provide information that a cDNA library cannot.

The bacteriophage lambda genome can exist in either a linear form or a circular form.

Diagram the resulting fragments as they would appear on an agarose gel after electrophoresis.

To create a cDNA library, cDNA can be inserted into vectors and cloned. In the analysis of cDNA clones, it is often difficult to find clones that are full length—that is, many clones are shorter than the mature mRNA molecules from which they are derived. Why is this so?

A hereditary disease is inherited as an autosomal recessive trait1. The wild-type allele of the disease gene produces a mature mRNA that is 1250 nucleotides (nt) long. Molecular analysis shows that the mature mRNA consists of four exons that measure 400 nt (exon 1), 320 nt (exon 2), 230 nt (exon 3), and 300 nt (exon 4). A mother and father with two healthy children and two children with the disease have northern blot analysis performed in a medical genetics laboratory. The results of the northern blot for each family member are shown here. Based on your analysis, what is the most likely molecular abnormality causing the disease allele?

A 2-kb fragment of E. coli DNA contains the complete sequence of a gene for which transcription is terminated by the rho protein. The fragment contains the complete promoter sequence as well as the terminator region of the gene. The cloned fragment is examined by band shift assay. Each lane of a single electrophoresis gel contains the 2-kb cloned fragment under the following conditions:

Lane 1: 2-kb fragment alone

Lane 2: 2-kb fragment plus the core enzyme

Lane 3: 2-kb fragment plus the RNA polymerase holoenzyme

Lane 4: 2-kb fragment plus rho protein

Diagram the relative positions expected for the DNA fragments in this gel electrophoresis analysis.

A 2-kb fragment of E. coli DNA contains the complete sequence of a gene for which transcription is terminated by the rho protein. The fragment contains the complete promoter sequence as well as the terminator region of the gene. The cloned fragment is examined by band shift assay. Each lane of a single electrophoresis gel contains the 2-kb cloned fragment under the following conditions:

Lane 1: 2-kb fragment alone

Lane 2: 2-kb fragment plus the core enzyme

Lane 3: 2-kb fragment plus the RNA polymerase holoenzyme

Lane 4: 2-kb fragment plus rho protein

Explain the relative positions of bands in lanes 1 and 3.

Variable number tandem repeats (VNTRs) are repeating DNA sequences of about 15–100 bp in length, found both within and between genes. Why are they commonly used in forensics?

Although the capture and trading of great apes has been banned in 112 countries since 1973, it is estimated that about 1000 chimpanzees are removed annually from Africa and smuggled into Europe, the United States, and Japan. This illegal trade is often disguised by simulating births in captivity. Until recently, genetic identity tests to uncover these illegal activities were not used because of the lack of highly polymorphic markers (markers that vary from one individual to the next) and the difficulties of obtaining chimpanzee blood samples. A study was reported in which DNA samples were extracted from freshly plucked chimpanzee hair roots and used as templates for PCR. The primers used in these studies flank highly polymorphic sites in human DNA that result from variable numbers of tandem nucleotide repeats. Several offspring and their putative parents were tested to determine whether the offspring were 'legitimate' or the product of illegal trading. The data are shown in the following Southern blot.

Examine the data carefully and choose the best conclusion.

a. None of the offspring is legitimate.

b. Offspring B and C are not the products of these parents and were probably purchased on the illegal market. The data are consistent with offspring A being legitimate.

c. Offspring A and B are products of the parents shown, but C is not and was therefore probably purchased on the illegal market.

d. There are not enough data to draw any conclusions. Additional polymorphic sites should be examined.

e. No conclusion can be drawn because 'human' primers were used.