MCAT Basics (from MedSchoolCoach) Genetics: Gene Expression
Oct 3, 2025
Delve into the intricacies of genetics, exploring X-linked and autosomal trait inheritance with real-life examples like color blindness. Understand the impact of epigenetic changes, DNA methylation, and genomic imprinting on gene expression. Discover the complexity of transcriptional control in prokaryotes and eukaryotes, including operons and chromatin remodeling. Learn about essential genetic lab techniques like PCR and FISH that aid in gene analysis and diagnostics, crucial for aspiring medical students.
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Why X-Linked Traits Target Males
- X-linked recessive traits affect males more because males have only one X chromosome and express any recessive allele they inherit.
- Females require two copies to express the trait, so fathers with a functional X can protect daughters from X-linked recessive diseases.
Memorize Classic Cross Ratios
- Memorize the monohybrid 3:1 and dihybrid 9:3:3:1 phenotypic ratios to speed up Punnett square problems.
- Use these ratios to quickly calculate frequencies for heterozygous parent crosses on the MCAT.
Parent‑Of‑Origin Expression
- Genomic imprinting silences one parental allele so expression depends on parent of origin.
- Imprinted genes express only the active parental copy, making them vulnerable to mutations and parent-specific inheritance patterns.