Club foot is one of the most common congenital skeletal abnormalities, with a world-wide incidence of about 1 in 1000 births. Both genetic and nongenetic factors are thought to be responsible for club foot. C. A. Gurnett et al. identified a family in which club foot was inherited as an autosomal dominant trait with reduced penetrance. They discovered a mutation in the PITXI gene that caused club foot in this family. Through DNA testing, they determined that 11 people in the family carried the PITXI mutation, but only 8 of these people had club foot. What is the penetrance of the PITXI mutation in this family

0.727

Explanation:

Penetrance can be defined as a measure of the association between a genotype and phenotype. In medical genetics, the penetrance of a mutation leading to the disease state is the proportion of individuals carrying the mutation and showing disease symptoms associated with such mutation. For example, if a mutation leading to the disease state has a 90% of penetrance, it is expected that 9 of each 10 individuals carrying the mutation will develop the disease, while the remaining 10% will not develop the disease. In this case, 8 of each 11 individuals carrying the PITXI mutation show symptoms compatible with the disease, and therefore the penetrance is 8/11 = 0.727 (73%).

the trilobite is used as an index fossil for various geologic time periods as specific types of the trilobites were present in different geological time periods. they are a group of marine arthropods belonging to the class of trilobita.

explanation:

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.