Test 50  (Genetics)

1. Chromosomal abnormalities are found in the following conditions:

a. achondroplasia

b. myeloid leukaemia

c. sickle cell disease

d. cri-du-chat disease

e. Patau syndrome

Answer
a.F   b.T   c.F   d.T   e.T
Myeloid leukaemia is associated with deletion of the long arm of chromosome 22 with translocation on to chromosome 9.
Cri-du-chat syndrome is caused by a partial deletion of the short arm of chromosome 5.
Trisomy 13 is a feature of Patau syndrome

2. Diseases associated with HLA-B8 include:

a. Sjogren's syndrome

b. multiple sclerosis

c. myasthenia gravis

d. insulin-dependent diabetes mellitus

e. Grave's disease

Answer
a.T   b.F   c.T   d.T   e.T
 

3. In Turner's syndrome:

a. premature cataract is common

b. the cells contains 45 chromosomes

c. the offsprings have 50% of inheriting the disease

d. there is an increased risk of hypertension

e. the patient is below the average height

Answer
a.F   b.T    c.F   d.T   e.T
In Turner's syndrome, the chromosomal make up is 46 XO. The patient is short but if growth hormone were given early, the final height may be normal. 
There is immature Mullerian structures resulting in infertility.
Hypertension is increased due to essential hypertension, renal abnormalities and coarctation of the aorta.

4. In Klinefelter's syndrome:

a. the karyotype is always 47XXY

b. the extra chromosome comes from the mother germ cells

c. there is an increased incidence of lens subluxation

d. the patient is infertile

e. there is an increased incidence of breast cancer

Answer
a.F   b.F   c.F   d.T   e.T
The karyotype may be 47XXY, XXXYY or XXYY.
The patient is tall and has bilateral gynaecomastia.
There is hypogonadism resulting in infertility.
The incidence of breast cancer is increased.

5. With regard to the DNA structures:

a. adenine (A) and guanine (G) are purine bases

b. guanine (G) always pairs with thymidine (T) and 
     adenine (A) with cytosine (C)

c. each DNA strands have a pentose-phosphate backbone 
    with projecting bases 

d. there are 64 possible codons

e. each amino acids may be coded by more than one codon.

Answer
a.T    b.F   c.T   d.T   e.T
Pyrimidine bases are thymidine (T) and cytosine (C)
G always pairs with C and T with A.