Genetics III

Mendel’s Second Law

the Law of Independent Assortment, states that genes for different traits segregate independently during gamete formation. This occurs in meiosis I, where homologous chromosome pairs align randomly at the metaphase plate, leading to genetic variation

two-factor (dihybrid) Punnett square

used to predict the genotypes of offspring for a two-factor cross, involving two genes, each with two alleles. The parental gametes are placed along the axes, and all possible allele combinations are filled in the squares. The resulting 16-box grid shows possible offspring genotypes and their probabilities

determining sex of the fruit fly, Drosophila melanogaster

Sex determination is based on the X-to-autosome ratio. A ratio of 1.0 (XX) results in a female, while a ratio of 0.5 (XY) results in a male

sex-linkage

refers to genes located on sex chromosomes (X or Y). In humans and Drosophila, X-linked traits (e.g., color blindness) are more commonly expressed in males since they have only one X chromosome and cannot mask recessive alleles

What are the segregation patterns of alleles from two physically linked genetic loci

Linked genes tend to be inherited together unless recombination occurs. The closer the loci, the less likely they are to be separated by crossing over

How do meiosis and chromosomal behavior influence allele segregation in linked genes?

During meiosis, linked genes on the same chromosome do not assort independently. Their segregation depends on recombination frequency, which is influenced by the distance between loci.

What role does meiotic recombination play in altering segregation patterns of linked alleles?

Meiotic recombination (crossing over) exchanges genetic material between homologous chromosomes, creating new allele combinations and altering expected inheritance patterns of linked genes.