Sunday, May 16, 2021
Mitochondrial Health

Genetic Inheritance, Autosomal Dominant, X-linked Recessive, Mitochondrial Disease Polygenic mtDNA

Autosomal Dominant Inheritance is when one allele, on any chromosome other than X or Y, is expressed over another allele of the same gene. This allele determines the phenotype (observable characteristics) and is referred to as dominant. The allele that is does not affect the phenotype is referred to as recessive. The dominant allele is often given the capital letter for a character while the recessive allele is given the lower case. Therefore, a heterozygous individual who is a carrier for the recessive gene would be represented as Aa. Usually on a pedigree nearly every generation has an affected individual.

Autosomal Recessive Inheritance is basically the opposite of autosomal dominant. Recessive alleles only change the phenotype when there is no dominant allele present. Heterozygous individuals do not show the phenotype of the recessive allele, but can pass this allele on to their offspring. These heterozygous individuals are called carriers. Usually on a pedigree few individuals are affected.

X Linked Recessive Inheritance is a type of recessive inheritance for genes on the X chromosome. Males express the phenotype when they inherit 1 effected allele, while females need to inherit 2 effected alleles. This is because the gene lies on the X chromosome, and males only receive a single X while females receive 2. Males cannot pass the effected X allele onto sons, because a son must receive a Y from the father to be male. Males are affected far more often than females. Women are very rarely affected by these disorders, and are primarily heterozygous carriers when they have the gene.

Mitochondria have DNA (mtDNA) that is circular and separate from the chromosomes in the nucleus. Mitochondrial Inheritance is only through the mothers and the fathers mitochondrial DNA is not passed onto children. Heterosplasmy is when a single individual has more than 1 type of mitochondrial DNA in their body due to mutations. The most common disease with this type of inheritance is Mitochondrial Myopathy which presents with “Ragged Red” muscle fibers on biopsy

Polygenic or Multifactorial Inheritance is when the phenotype is not dictated by a single gene locus. These types of diseases are determined by an interaction between many contributing genetic and environmental factors.
Variable Expressivity = same genetic defect presents differently in different patients. Neurofibromatosis is an example
Mosaicism = when populations of cells within a single individual have different genotypes due to post-fertilization changes. Often in reference to chromosomal abnormalities caused by improper mitosis. Germline Mosacism is when only gametes (sperm and eggs) are affected by the genetic defect. Therefore, the individual would not show signs of the disease, but they could pass it on to their offspring
Pleiotrophy = a single genetic defect has multiple effects (same gene is expressed in many different tissues)
Incomplete Penetrance = not everyone with genetic defect gets the disease. Low penetrance means many people with the genotype do not show the phenotype

Pictures Used (In order of appearance)
• “Autosomal Dominant” by Domaina available at ttp:// via Creative Commons 3.0 Attribution Share Alike
• “XlinkedRecessive” by US National Library of Medicine available at via Public Domain
• “Mitochondrial” By US National Library of Medicine available at by Public Domain


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17 thoughts on “Genetic Inheritance, Autosomal Dominant, X-linked Recessive, Mitochondrial Disease Polygenic mtDNA
  1. If you liked this video and want me to make more please let me know by commenting, liking this video or by subscribing to my Youtube channel. If you have a question, please don’t hesitate to ask and I’ll try to answer it ASAP. 

  2. Thanks, this video was helpful , but one suggestion do it a bit more comprehensive .
    Please can you do a detail videos along with clinical scenarios on genetic mapping and diagnosis   

  3. Well now Britains trying to stop genetic diseases from passing from mother child, with that new three person babies breakthrough, I think they're starting to play God alittle now.

  4. Hey man! If you're trying to use a great mnemonic to remember the inheritance pattern of the actual diseases, I have a song on my channel that teaches you how to sing them out to the tune of a famous lullaby. I would appreciate it if you could check it out! Love your stuff. Keep it up

  5. hello! great videos! extremely helpful and easy to understand. I take step 1 in the next couple of months. i am reviewing first aid and watching your videos as i follow along. im also doing u world questions. would you say this is suffice? also- do you have a video where you share your step 1 experience and how well you did? thank you so much!! 🙂

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