Today’s Agenda: Questions from Chapter 1 Introduce key ideas in Chapter 2: Single Gene Inheritance

Single Gene Inheritance Identify if the phenotype is due to a single gene…..where do we begin?

Start with a look at mutants…. Is this forward or reverse genetics? What is the inheritance ratio?

Genes are part of chromosomes

Chromosomes have unique regions What is the function of each of these regions?

Genome of Muntjac How many chromosomes? Is this organism haploid or diploid?

Map of Genes and Chromosomes

Map of Genes and Chromosomes

Mendel was first to study single gene inheritance

What did Mendel find? ? ?

The F2 ratios are the same!

What did Mendel’s work establish?

Meiosis is key in the segregation of chromosomes

Synapsis increases variation FIGURE: Model of the synaptonemal complex (SC).  Lateral elements (light blue rods) of homologous chromosomes align and synapse together via a meshwork of transverse filaments (white lines) and longitudinal filaments (dark blue rods).  The longitudinal filaments are collectively referred to as the "central element" of the SC.  Ellipsoidal structures called recombination nodules (e.g., gray ellipsoid) are constructed on the central region of the SC.  (Image: Mississippi Genome Exploration Lab)

How are gametes formed in haploid organisms?

Single-Gene inheritance at DNA level

Map of Mutations

More about alleles…… Dominance Recessiveness Haplosufficient Haploinsufficient

What’s unusual about white-eyed fruit flies? Watch for new terms: What does it mean to be hemizygous? What’s a pseudoautosomal region?

Some genes are found on sex chromosomes

What is the inheritance pattern of genes on sex chromosomes?

Crosses of the F1

Pedigrees Analysis to represent inheritance

Summary Single gene inheritance patterns Perform a cross of organisms using wild type and mutant Confirm the genotype of the wild type by performing a testcross Look for phenotypic ratios of 3:1, 1:1 and genotypic ratios of 1:2:1 Sex-linked genes have different phenotypic ratios in the two sexes of progeny AND different ratios in reciprocal crosses