SIngle Gene disorders

Question 1

2 autosomal Dominant types?

Answer 1

Loss of function- defects in structural proteins

Gain of function- normal proteins with toxic properties. (gain of function bad e.g. huntington disease)

Question 2

What is a disease that is autosomal dominant and has spots on the eye?

Answer 2

Neurofibromatosis Type 1

Question 3

This is a diagnostic tool in the clinical setting for Neurofibromatosis type 1. (know it)

Answer 3

Lisch Nodules

Question 4

Important genetic concept that is epitomized by Neurofibromatosis Type 1.

Answer 4

variable expression- even within the same family

Question 5

What is a disease that is autosomal dominant that involves pleiotropy?

Answer 5

Marfan syndrome

Question 6

When a single mutation affects multiple organ systems a common feature of many genetic diseases.

Answer 6

Pleiotropy

Question 7

What are some disorders involved with marfan syndrome?

Answer 7

Hypermobile joints
Cardiovascular disease
Skeletal abnormalities (thin long limbs and fingers)

Question 8

What is the most common single gene disorder in the world and is autosomal recessive?

Answer 8

Thalassemia (‘thalassa’ means sea)

Question 9

Thalassemia causes premature death of cells destined to become red blood cells- results in ______________.

Answer 9

Hemolytic anemia

Question 10

What disease makes you resistant to malaria?

Answer 10

Thalassemias

Question 11

Males need only one copy of a defective ________ gene whereas females would need 2 copies of a defective __________ gene to show symptoms.

Answer 11

X-linked gene

Therefore phenotype issues are much more common in males.

Question 12

Bleeding into the joints, causes swelling and loss of joint mobility

Answer 12

Hemarthosis

Question 13

Most frequent cause of death with someone that has hemophilia A and B is what?

Answer 13

AIDS

Question 14

Why is AIDS the most common cause of death with Hemophilia? (IMPORTANT)

Answer 14

The way we treat hemophilia is blood transfusion, in order to maintain blood clotting factor, you can’t treat the blood, so it may still contain diseases like AIDS.

Question 15

Females have 2 copies of x chromosome, if no transcription control mechanism there would be a 2 fold excess of genes. What is the control mechanism?

Answer 15

X inactivation also called LYONIZATION (important)

Question 16

What can explain why some female heterozygotes with one mutant X chromosome can show symptoms of an X-linked recessive disease.

Answer 16

X inactivation

Question 17

What are some diseases that are rare cases of gene disorders that do not manifest until later in life?

Answer 17

Huntington disease (onset age 30 or 40s in first symptomatic generation)
Myotonic Dystrophy- same as above

Question 18

When the same disease phenotype can be caused by mutations in different loci (i.e. in different genes)

Answer 18

Locus Heterogeneity

Question 19

All genetic disease begins with a __________.

Answer 19

New mutation

Question 20

True/False: In cases with high mortality or low fertility it is often due to a new mutation. The disease will spread easily within the population.

Answer 20

False! people dying= hard to keep the mutation alive

new mutation typically get weeded out

Question 21

This refers to diseases where the most recent generations of affected individuals have an earlier onset and more severe symptoms than previous generations.

Answer 21

Anticipation

Question 22

Anticipation is most often associated with diseases caused by ___________________. (i.e. fragile X syndrome, myotonic dystrophy, Huntington disease)

Answer 22

Trinucleotide repeat expnsions

Question 23

With anticipation, eventually (even though considered an adult disease) later generations symptoms may first appear in childhood, due to what?

Answer 23

Expansion of the trinucleotide repeat

Question 24

What are the assumptions of HWE?

Answer 24

Large Population
Random Mating
Constant and predictable relationship between genotype frequencies and gene frequencies.

Question 25

p+ q=1

If p=0.4 then what does q=?

Answer 25

q=

1-0.4=0.6

Question 26

What is HWE equation?

Answer 26

p^2 + 2pq + q^2 = 1

Question 27

If p= 0.99 and q=0.01

what is the likelihood of a person being a carrier?

Answer 27

(pp)= 0.99^2= 0.98
pq= 2pq= 2x0.01x0.99 = 0.02
or 1/50 (thus number of carriers for PKU is about 1 in 50)

Question 28

Ultimately what is the primary source of all new genetic variation in populations.

Answer 28

Mutation

Question 29

True/False: In general mutation rates change pretty often.

Answer 29

False, stable and slow

Question 30

Heterozygotes for the sickle cell mutation have some resistance from ________… This is a good example of what?

Answer 30

malaria

Heterozygote advantage

Question 31

Heterozygotes for the cystic fibrosis mutation are protected against what?

Answer 31

typhoid fever

Question 32

This influences gene frequencies by selecting for genes that promote survival or fertility (referred to as fitness)

Answer 32

Nat selection

Question 33

Very rare autosomal recessive disorder that has symptoms of polydactyly and short-limbed dwarfism.
Caused by defective EVC gene, unknown function

Answer 33

Ellis van Creveld disease