Genetic Conditions

Question 1

What gene is affected in CF?

Answer 1

CFTR gene on chromosome 7

Question 2

How does the genetic fault cause the symptoms seen in CF?

Answer 2

CFTR gene codes for a faulty chloride ion channel, the reduced functionality of the channel causes a build up of mucus in the airways.

Question 3

Haemophilia A is linked to which chromosome, and what does this mean for its presentation in genders?

Answer 3

X, meaning women are mostly unaffected because they would have another version of the X chromosome with a “normal” gene.

Question 4

What gene does Haemophilia A affect?

Answer 4

Factor VIII gene

Question 5

People with Haemophilia A should avoid which common drug class?

Answer 5

NSAIDs

Question 6

What is the current estimate of the incidence of CF in Western Europe?

Answer 6

1/4500

Question 7

Which ethnicity is CF more prevalent in?

Answer 7

Caucasian

Question 8

Phenylketonuria is an autosomal “what” disorder?

Answer 8

recessive

Question 9

Name a Y-linked disorder?

Answer 9

Webbed toes

Question 10

Name two X-linked disorders

Answer 10

Haemophilia A and Red-Green colour blindness

Question 11

Sickle cell anaemia affects what structure, and what effect does this have on the function of this structure?

Answer 11

The shape of haemoglobin creates “sickle shaped” red blood cells, this reduces their ability to carry oxygen and can also cause them to get stuck in capillaries.

Question 12

Familial hypercholesterolemia is autosomal “what”?

Answer 12

Dominant

Question 13

What gene is affected in familial hypercholesterolemia?

Answer 13

Low Density lipoprotein receptor (LDLR)

Question 14

What does phenylalanine hydroxylase do, and why is it important?

Answer 14

Converts phenylalanine from our digested food into tyrosine. Tyrosine is important in thyroid hormone production and overall metabolism in the body. This affects development and cognitive function.

Question 15

PKU is an autosomal recessive disorder, what probability is there of affected offspring if their parents are both carriers?

Answer 15

25%

Question 16

What is aneuploidy?

Answer 16

Higher or lower numbers of chromosomes

Question 17

What are the most common chromosomal abnormalities?

Answer 17

Deletion, translocation, inversion and duplication

Question 18

The genetic disorder PKU affects the production of what enzyme?

Answer 18

Phenylalanine hydroxylase

Question 19

How common is PKU in the UK?

Answer 19

1/10,000

Question 20

Roughly how many inborn errors of metabolism are there?

Answer 20

Over 200

Question 21

Without treatment, what is the life expectancy of homozygous familial hypercholesterolemia?

Answer 21

Less than 20 years

Question 22

Familial hypercholesterolemia occurs in how many people in the UK?

Answer 22

1 in 250

Question 23

What type of congenital genetic disease is Down’s Syndrome?

Answer 23

Spontaneous

Question 24

What genetic error is Down Syndrome (trisomy) caused by?

Answer 24

An extra copy of chromosome 21

Question 25

95% of Down Syndrome cases are caused by what, and what is it?

Answer 25

Nondisjunction, the spindle fibres fail to separate the sister chromatids in either step one or two of meiosis, creating some gametes with a missing chromosome and some cells with an extra chromosome.

Question 26

Apart from nondisjunction, what are the other two genetic error processes that can cause Down Syndrome?

Answer 26

Robertsonian translocation where parts of two chromosomes switch, creating lost or copied genetic material (4%) and mosaic where an error in mitosis creates a mixture of cells with normal amount of chromosomes and some with an extra chromosome (1%)

Question 27

What effects can Down Syndrome have on the heart?

Answer 27

Increased risk of septal defects

Question 28

What is the most common risk factor for down syndrome?

Answer 28

Maternal age