Inheritance of Genetic Disorders (11c Group 4) by Heather Murray https://padlet.com/hglenville/a0if16vw6edgab9h en-us 2021-02-21 16:16:50 UTC 2021-02-23 14:19:05 UTC hello@padlet.com Autosomal Dominant Disorders https://padlet.com/hglenville/a0if16vw6edgab9h/wish/1228778527 What are they and how do they occur? 
  • Occurs when a child inherits an abnormal gene from one of their parents and the abnormal gene is the dominant one
    • The child only needs 1 of the abnormal genes in order to have the disease because the dominant, abnormal one overpowers any recessive, normal genes. 
  • Mutations are found on 1 of the 22 autosomal chromosomes (not an X or Y). 
  • A person with an autosomal dominant disorder has a 50% chance of giving the disease to their child (when they have 1 mutated gene themselves). 

Huntington's Disease: 
  • Causes progressive breakdown of nerve cells in the brain. 
  • Symptoms usually appear in 30s-40s (before age 20 it’s called juvenile Huntington’s disease). 
  • Leads to many difficulties with slow or uncontrollable movement; difficulties with creating thoughts and learning new information; and many mental illnesses. 
  • Is caused by a mutation in the dominant huntingtin gene where they have an abnormally long list of CAG codons in their DNA. 
    • Normally it’s ≤ 20 & codes for a protein that’s thought to be important for nerve cells to work properly. 
    • Mutated it’s ≥ 36 & codes for a mutated huntingtin protein that has a long tail of glutamine. 
      • This protein is toxic and thought to be killing nerve cells in the brain. 
  • The sticky tails of the mutated huntingtin protein cause multiple proteins to stick together. 
  • While it is still in the process of being researched, scientists know that when these proteins enter the nucleus of nerve cells, they cause problems and cause the cells to break down. 
  • Is autosomal dominant, meaning that it occurs on 1 of the 22 autosomal chromosomes and only 1 mutated gene is needed to have the disease. 
  • A person with 1 mutated gene has a 50% chance of giving their child the disease. 
  • Time from disease emergence to death of person is 10-30 years (for juvenile Huntington's disease death usually happens within 10 years). 
  • First people need help with all their daily living & care activities, then they will be confined to a bed and unable to speak by the end. 
  • There is no cure available yet since scientists still don’t know how the proteins cause nerve cells to break down. 

Marfan Syndrome: 
  • Caused by a gene defect in the dominant, fibrillin-1 gene. This gene plays a role as a building block for connective tissues in the body. 
  • Causes bones to grow very long (people with Marfan syndrome usually have really long arms & legs). 
  • Also affects the lungs, aorta (heart), eyes, and skin. 
  • When Marfan affects the heart, the person’s lifespan is much shorter than normal. However, people with this who do not have as many heart problems usually live well into their 60s. 
  • Symptoms are a chest that sticks in/out, flat feet, nearsightedness, scoliosis (curved spine), and chronic muscle/joint pain. 
]]> 2021-02-22 21:10:16 UTC https://padlet.com/hglenville/a0if16vw6edgab9h/wish/1228778527 Sex Linked Inheritance https://padlet.com/hglenville/a0if16vw6edgab9h/wish/1229355139 Sex linked diseases are passed down threw the X and Y chromosomes, but most often the term sex-linked is referring to X-linked, and the term is used interchangeably.

Dominant inheritance happens when only one of the X or Y chromosomes with an abnormality is needed for the child to inherit the disease.

Recessive inheritance is when both matching genes must be abnormal to cause the disease, if only one is abnormal either the disease won’t occur or the symptoms are mild.  These people are called carriers, and can pass the gene to their children. Recessive Sex-linked traits are more abundant than dominant. Men are most vulnerable to these diseases because they have only one X-chromosome, if that chromosome has the abnormality it will be expressed. In women there is a second X-chromosome, and it can be used to express proteins that the abnormal chromosome can’t. This means that women are more likely to be carriers, while men can’t be carriers and are more likely to inherit the disease. This also means men can’t pass the diseases onto their sons

Y-linked disease are very rare and can only be passed from father to son.

Colour Blindness
Males are significantly more likely to inherit red-green colourblindness because it is a sex-linked (X-linked) recessive trait. In girls two abnormal X-chromosomes are needed to express colourblindness, while in men only one is needed. 

Haemophilia
Haemophilia is a rare condition that limits the body’s ability to clot. People affected bleed longer when cut, bruise easily, and are more affected by minor internal bleeding (causing stiff joints). 
It's recessive and X-linked, meaning it's significantly more common in males. Carriers (always female) have enough clotting factors for a normal amount of clotting, however about 10% have less than the normal amount and are at risk for abnormal bleeding (ie after a tooth extraction, surgery or injury).

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