Genetics Concepts

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Chi Squared Function

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- Used to determine whether the difference between observed and expected frequency distribution is statistically significant

- If your chi-squared value is greater than the critical value, then we assume that the traits are linked (did not assort independently)

- If your chi-squared is less than c.v., then the trait appears to independently assort (we got 1.62, so ind. assort)

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Terms in this set (13)

Chi Squared Function

Punnet Grid

Recombinant Frequencies

(number of recombinants/total number) x100

Genetic Disorders

- Medical research has identified over 4000 genetic diseases!

- Most of them are due to recessive alleles and are very rare (it is rare to get the allele and even more rare to get from both parents!)

- Sequencing the genome of an individual is becoming more affordable, so we are learning more about how many recessive genetic alleles a typical human carries

Huntington's Disease

Cause-

Huntington's Disease (HD) is a brain disorder that affects a person's ability to think, talk, and move.

The disease destroys cells in the basal ganglia, the part of the brain that controls movement, emotion, and cognitive ability. HD is caused by a mutation in a gene on chromosome 4. The job of its protein product, huntingtin, is to direct the delivery of small packages (vesicles containing important molecules) to the outside of the cell. Normally, the coding region of this gene contains the DNA sequence "CAG" repeated again and again. The number of times this triplet is repeated varies from person to person, ranging from 10 to 26 times. People with HD have an abnormally high number of these CAG triplets, approximately 40 or more. This likely disrupts the function of the gene's protein product, but how the expansion of the CAG repeat causes disease is unknown. Somehow the brain cells of HD patients accumulate clumps of protein that become toxic, resulting in cell death. Some patients lose more than 25% of their brain cells before they die.

Symptoms-

Huntington's disease affects the part of the brain that controls thinking, emotion, and movement. Most people who have the disease start to see symptoms between the ages of 30 and 50 (but symptoms can appear earlier or later in life). The disease gets worse over time.

Symptoms include poor memory, depression and/or mood swings, lack of coordination, twitching or other uncontrolled movements, and difficulty walking, speaking, and/or swallowing. In the late stages of the disease, a person will need help doing even simple tasks, like getting dressed.

Treatment-

Treatments do not slow the progression of the disease, but they can help make the patient more comfortable. Medications ease feelings of depression and anxiety; others control involuntary movements. Physical or speech therapy helps HD patients lead more normal lives.

Other-

The disease was named for Dr. George Huntington, who first described it in 1872.

In the United States, about 1 in every 30,000 people has Huntington's disease.