Genetics Chapter 7: Linked Genes

Linkage and Recombination

• Linked genes do not assort independently and are inherited together due to their proximity on the same chromosome.
• Recombination frequency, influenced by gene distance, helps predict inheritance patterns between linked genes.

Principles of Genetics

• Principle of Segregation: Each diploid organism has two alleles for a locus that separate during meiosis; one allele goes to each gamete.
• Principle of Independent Assortment: Alleles at different loci segregate independently during gamete formation.

Key Concepts in Linkage

• Locus refers to the specific position of a gene or mutation on a chromosome.
• Linked genes are situated close on the same chromosome, while linkage groups refer to sets of genes that travel together during meiosis.

Types of Progeny

• Non-recombinant progeny (parentals) consist of original allele combinations.
• Recombinant gametes have new combinations of alleles due to crossing over.

Genetic Testing

• A testcross involving linked genes results in two progeny types reflecting the P generation traits, unlike independent assortment, which yields a 1:1:1:1 ratio of progeny types.
• Chi-square tests can determine gene linkage.

Recombination Dynamics

• Recombination frequency is calculated as (#recombinants/ total # progeny) x 100, indicating the extent of genetic mixing.
• Interchromosomal recombination occurs between genes on different chromosomes, whereas intrachromosomal recombination happens among genes on the same chromosome.

Gene Configuration

• Coupling (cis) configuration places wild-type alleles on one chromosome and mutant alleles on the homologous chromosome.
• Repulsion (trans) configuration has each chromosome carry one wild-type and one mutant allele.

Mapping Genetics

• Genetic maps illustrate the relative distances between genetic loci based on recombination rates, expressed in map units or centiMorgans.
• Physical maps depict actual distances, measured in base pairs.

Two-Point Testcross Considerations

• Distinguishing genes on different chromosomes from those far apart on the same chromosome can be challenging when recombination is at 50%.
• Testcrosses for distantly located genes can underestimate their physical distance due to unobserved double crossovers.

Double Crossovers

• Double crossover events involve two separate crossover occurrences between two loci, complicating genetic predictions and inheritance patterns.

Explore the concepts of linked genes and their inheritance patterns in this flashcard quiz. Learn how recombination affects gene linkage and the principle of segregation. Test your understanding of genetic linkage and the distance-dependent frequency of recombination.