In German cockroaches, bulging eyes (b u) are recessive to...

In German cockroaches, bulging eyes $(b u)$ are recessive to normal eyes $\left(b u^{+}\right)$ and curved wings $(c v)$ are recessive to straight wings $\left(c v^{+}\right) .$ Both traits are encoded by autosomal genes that are linked. A cockroach has genotype $b u^{+} b u c v^{+} c v,$ and the genes are in replusion. Which of the following sets of genes will be found in the most-common gametes produced by this cockroach? a. $b u^{+} c v^{+}$ b. bu c $v$ c. $b u^{+} b u$ d. $c v^{+} c v$ e. bu $c v^{+}$ Explain your answer.

In German cockroaches, bulging eyes $(b u)$ are recessive to normal eyes $\left(b u^{+}\right)$ and curved wings $(c v)$ are recessive to straight wings $\left(c v^{+}\right) .$ Both traits are encoded by autosomal genes that are linked. A cockroach has genotype $b u^{+} b u c v^{+} c v,$ and the genes are in replusion. Which of the following sets of genes will be found in the most-common gametes produced by this cockroach?
a. $b u^{+} c v^{+}$
b. bu c $v$
c. $b u^{+} b u$
d. $c v^{+} c v$
e. bu $c v^{+}$
Explain your answer.

Key Concepts

Genetic Linkage

Genetic linkage refers to the phenomenon where genes that are located close together on the same chromosome tend to be inherited together. Unlike independently assorting genes, linked genes do not normally follow the typical ratio of independent assortment predicted by Mendel's laws, unless crossing over occurs between them during meiosis.

Repulsion (or Coupling) Phase

The arrangement of alleles on homologous chromosomes can be classified as either coupling or repulsion. In repulsion, also known as the heterozygous configuration in which one chromosome carries one dominant trait allele and the other carries the alternate recessive trait allele, the most common gametes produced (parental gametes) reflect the original non-recombinant combinations. This concept is crucial when predicting gamete formation in traits encoded by linked genes.

Parental versus Recombinant Gametes

During gamete formation, the most frequent (parental) gametes are those that reflect the original arrangement of alleles on the chromosomes. When genes are linked and in repulsion, these parental gamete types will include one gamete with the dominant allele for one trait and the recessive allele for the linked trait, and the other gamete with the opposite combination. Recombinant gametes, resulting from crossing over, are less common and differ from the original allele configurations.

Autosomal Inheritance

Autosomal inheritance refers to genes located on non-sex chromosomes. Traits determined by autosomal genes are inherited equally by both sexes. Understanding autosomal inheritance is essential for analyzing how traits are passed to offspring, especially when considering phenomena like linkage and the formation of parental and recombinant gametes.

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