10) Exceptions to Mendelian genetics: Linkage, crossing over, uniparental inheritance

Question 1

Linkage

Answer 1

• Two genes/alleles present on the same chromosome
• Cannot assort independently → Linked together
• Chromosomes tend to stick together

Question 2

Crossing over

Answer 2

• During meiosis
• Intrachromosomal recombination
• Homologous chromosome pair make contact with each other
• Genetic information is exchanged

Question 3

Uniparental inheritance

Answer 3

• Transmission of genes to offspring from only one of the parents
• Genomic imprint
• Maternal inheritance: mtDNA

Question 4

Genomic imprint

Answer 4

1. Gene inactivation (maternal or paternal)
2. 3 allelic/genotype variants occur
3. Gene expressed in a parent-of-origin specific manner

Question 5

Maternal inheritance: mtDNA

Answer 5

• Mitochondrial diseases
• Involve replication and transmission of mtDNA
• Phenotypic differences controlled solely by cytoplasmic factors from the maternal parent