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4. What is quantitative trait loci (QTL) analysis and how does it help us understand the genetics of phenotypic traits? 5. Scientists use a variety of methods to construct phylogenetic trees. Name three of the five common methods/techniques and discuss how they are used to construct phylogenetic trees. 6. Describe two (of the four) ways mutations to a regulatory network may affect the development of an organism.

Answer 1

1. Quantitative trait locus (QTL) analysis is defined as a statistical analysis based on genetics to establishes link between phenotypic and phenotypic data to explain the variation in complex trait. In this test, strains of genetically different organisms for example size of egg in hen and ostrich. Now researcher require genetic marker detail that distinguishes the two set of parental genetic line. This is genotyping. Common markers used are –

a) Single nucleotide polymorphisms (SNPs)

b) Simple sequence repeats

c) Restriction fragment length polymorphisms (RFLPs) etc.

Linked markers will show association with phenotype while unlinked markers do not show any association with phenotypes.

2. The three methods are

a) Distance-matrix methods – In this method, the genetic distances between sequences is measured and on that basis proportion of mismatched positions is calculated. Then a matrix is prepared with genetic sequence distances.

b) Maximum parsimony – In this method, length of branch of tree is reduced by reducing the number of evolutionary changes required between sequences. However, the most optimal tree would be the one with fewest mutations or the shortest one.

c) Maximum likelihood – Probable location of nucleotide position is determined and then tree is constructed for ancestral sequences possessed by specific nucleotide

3. Two regulatory mutations are

a) Haploinsufficiency – As per this only one copy of gene is not enough

b) Antimorphic or dominant negative – In this the defective gene interferes with the functioning of wild type genes.