New Rules For Heredity (Non-Mendelian Inheritance of Epigenetics) (EP 44)

Hosted by Lester Nare and Krishna Choudhary, this episode marks Krishna’s return to the studio after paternity leave — and the timing could not be more fitting. Today’s deep dive is about inheritance: not just the classic Mendelian rules most of us learned in biology class, but the stranger, more dynamic world of non-Mendelian epigenetic inheritance. Starting from Gregor Mendel and his pea plants, Lester and Krishna rebuild the foundations of genetics from first principles: dominant and recessive alleles, Punnett squares, chromosomes, fruit flies, DNA, and the physical mechanism behind inherited traits. Then they move into the “software layer” of biology: epigenetics, DNA methylation, chromatin packaging, RNA interference, and paramutation — cases where the genetic code is present, but the cell’s machinery silences or rewrites how that code is used. The episode centers on a new Nature Genetics paper, “Non-Mendelian inheritance of DNA methylation patterns in mice,” which suggests that non-Mendelian epigenetic inheritance may be more widespread in mammals than previously understood. The conversation also covers why Oxford Nanopore sequencing made this kind of analysis possible, why methylation patterns can be hard to trace across generations, and what all of this could mean for disease risk, drug response, sex differences, evolution, and the long-running nature-versus-nurture debate. Support the show Donate: FFPod.com/donate Follow: @FFPod on X / Instagram / TikTok / Facebook Comment prompts: What books should we add to the FFP bookshelf? Chapters 00:00 Intro 00:59 Krishna returns from paternity leave 01:59 Today’s topic: non-Mendelian epigenetic inheritance 02:15 Questions of inheritance and fatherhood 03:24 DNA hardware vs. epigenetic software 05:23 Why epigenetics matters for disease and inheritance 05:54 The 7% finding and the quiet revolution in heredity 06:58 Generational trauma, epigenetics, and why now 09:00 Gregor Mendel and the birth of genetics 10:34 Why Mendel chose pea plants 12:45 Controlled breeding and true-breeding lines 15:26 Mendel’s purple and white flower experiment 17:26 Dominant and recessive traits 18:31 The law of segregation 21:15 Why the 3:1 ratio appears 21:53 Independent assortment 24:06 Mendel is ignored, then rediscovered 25:17 From mathematical rules to biological mechanisms 26:36 Chromosomes and the physical basis of heredity 27:08 Thomas Hunt Morgan and fruit flies 29:22 Sex-linked inheritance 31:29 Linked genes and the first major crack in Mendel 33:37 Why fruit flies became a foundational model organism 34:18 Caltech, Morgan, and the genetics lineage 36:34 DNA, Watson, Crick, and Rosalind Franklin 37:33 How DNA stores genetic information 40:52 Eye color and dominant vs. recessive alleles 42:15 Housekeeping, studio updates, and support 44:11 Paramutation and maize 47:11 When the expected dominant trait disappears 48:28 The purple gene gets silenced 51:33 DNA methylation explained 52:41 Chromatin, histones, and gene packaging 55:04 RNA interference as a mobile silencer 57:40 Why this is non-Mendelian epigenetic inheritance 1:00:15 Why mammals were hard to prove 1:01:44 Bisulfite sequencing and methylation detection 1:03:35 The problem with short reads 1:05:02 Allelic phasing: which parent did it come from? 1:06:59 The Oxford Nanopore revolution 1:09:31 Ultra-long reads and methylated cytosines 1:11:15 Portable sequencing and the MinION 1:13:28 The Nature Genetics mouse paper 1:15:09 Collaborative cross mice 1:16:03 The experimental design 1:17:39 Building a pseudo-hybrid reference genome 1:19:41 The Mendelian methylation baseline 1:21:47 Non-Mendelian methylation anomalies 1:23:21 CAPN11 and paramutation in mammals 1:25:28 Emergent epigenetic patterns 1:27:42 Organ- and sex-specific methylation 1:29:27 Clinical genetics and evolutionary implications 1:31:45 Nature versus nurture becomes nature and nurture 1:32:50 Disease risk and silenced healthy alleles 1:34:33 Looking for paramutation in humans 1:35:21 Final thoughts 1:36:16 Comment prompts 1:36:51 Outro Show Notes • Primary paper: “Non-Mendelian inheritance of DNA methylation patterns in mice,” Nature Genetics https://www.nature.com/articles/s4158... Oxford Nanopore: How nanopore sequencing works https://nanoporetech.com/platform/tec... Thomas H. Morgan — Nobel Prize facts https://www.nobelprize.org/prizes/med... Mendel’s “Experiments in Plant Hybridization” http://www.esp.org/foundations/geneti... Prior FFP episode on DNA, Watson, Crick, and Rosalind Franklin    • The Race to the Double Helix — Watson, Cri...