Fragile X Syndrome - Inheritance

Doctor Gul Dolen explains that Fragile X syndrome is not a mendelian disorder, because the inheritance pattern in slightly different.

Fragile X is a little bit different from a Mendelian disorder because when we say Mendelian genetics we mean usually that you have a mutation on one gene, and it’s passed directly down to the next generation and Fragile X is a little bit different. What’s passed down is the tendency for the gene to be methylated. So, every person has parts of their chromosome that have repeated areas. They are sequences that are called CG repeat areas, and those are found scattered throughout the genome in everybody. But parents of children with Fragile X, the mother, will have little islands where those repeats are more than is normal in the general population and those mothers are called premutation carriers. When you have an expansion of that repeat there is a tendency for it, in the next generation, to expand further. When that repeat-expansion goes beyond 200, then you get Fragile X. So it’s not a Mendelian disorder because there is a change in one generation, that means that the mother doesn’t have it but the child does and so strictly speaking it’s not a Mendelian inheritance pattern.

fragile x syndrome, inheritance pattern, mendelian inheritance, chromosome, genome, mutation, sequences, next generation, genetics, tendency, population, gul, dolen

Related Content

15945. What is Fragile X?

The FMR1 gene produces a protein involved in making cellular connections in the brain.

  • ID: 15945
  • Source: DNAi

2363. Fragile X Syndrome

Doctor Gul Dolen describes the key characteristics of Fragile X syndrome, which can include problems with language, mental retardation, and symptoms of autism.

  • ID: 2363
  • Source: G2C

15946. What causes Fragile X?

The FMR1 gene produces a protein involved in making cellular connections in the brain. If this gene carries many repeats of the nucleotides CGG at one end, it is deactivated. People with this mutation display mental impairments or retardation. Fragile X s

  • ID: 15946
  • Source: DNAi

2368. MGluRs and Treating Different Autisms?

Doctor Gul Dolen explains that there are many single-gene disorders on the autism spectrum, which may or may not respond to mGluR-related treatment.

  • ID: 2368
  • Source: G2C

2367. Biochemical Treatments for Autism?

Doctor Gul Dolen discusses how new biochemical treatments for Fragile X Syndrome may be used to treat autism.

  • ID: 2367
  • Source: G2C

15898. Fragile X syndrome

The FMR1 gene produces a protein involved in making cellular connections in the brain. If this gene carries many repeats of the nucleotides CGG at one end, it is deactivated. People with this mutation display mental impairments or retardation. Fragile X s

  • ID: 15898
  • Source: DNAi

2366. Biochemical Breakthrough - Fragile X Syndrome

Doctor Gul Dolen discusses the significance of finding a potential biochemical treatment for the neurological disorder, Fragile X syndrome.

  • ID: 2366
  • Source: G2C

15977. Maternal inheritance

Unlike nuclear DNA, mtDNA is  inherited solely from the mother. (Mitochondria are predominantly from the mother’s egg and not from the father’s sperm.) Therefore, mtDNA sequences or orders of nucleotides generally remain constant over many generation

  • ID: 15977
  • Source: DNAi

11507. Exhibit, "Color Inheritance in Guinea Pigs" (Mendelian pattern)

Exhibit, "Color Inheritance in Guinea Pigs" (Mendelian pattern)

  • ID: 11507
  • Source: EA

16263. Chromosomes carry genes.

DNAFTB Animation 10:Thomas Hunt Morgan describes his discoveries using fruit flies.

  • ID: 16263
  • Source: DNALC.DNAFTB