Mechanisms Of Human Disease

Question 0

Give examples of intrinsic factors.

Answer 0

Genetic, metabolic, cellular, structural.

Question 1

Give examples of extrinsic factors.

Answer 1

Physical, chemical, biological, nutritional.

Question 2

Microscopically detectable numeric or structural chromosomal changes is termed what?

Answer 2

Cytogenetics.

Question 3

Sub-microscopic changes involving one or more nucleotides is termed what?

Answer 3

Molecular genetics.

Question 4

What causes genetic mutations?

Answer 4

DNA damage from environmental or chemical agents (e.g. UV, ionising radiation, alkylating agents). 
Genetic events (e.g recombination - exchange of DNA between chromosomal segments).

Question 5

Give examples of chromosomal abnormalities.

Answer 5

Deletion, translocation (reciprocal, two chromatids exchange DNA segments) inversion (non-reciprocal, one chromatid donates DNA to another), ring formation.

Question 6

Name two monogenic diseases.

Answer 6

Cystic fibrosis, sickle cell anemia.

Question 7

Name two polygenic diseases.

Answer 7

Diabetes, bronchial asthma.

Question 8

What is nondisjunction?

Answer 8

The failure of chromosome pairs to separate properly during cell division in gametogenesis.

Question 9

What are structural abnormalities?

Answer 9

Deletion, translocation.

Question 10

What do karyotypes show?

Answer 10

The number of chromosomes and what they look like under a light microscope. Attention is paid to their length, the position of the centromeres, any differences between the sex chromosomes and any other physical characteristics. The preparation and study of karyotypes is part of Cytogenetics.

Question 11

Define haploid.

Answer 11

23 chromosomes, e.g in a sperm or ovum.

Question 12

Define diploid.

Answer 12

46 chromosomes, e.g in a somatic cell.

Question 13

Define polyploidy.

Answer 13

3 or more times the haploid number of chromosomes.

Question 14

Define aneuploidy.

Answer 14

Chromosome number that is not multiple of 23.

Question 15

Define autosomal dominant.

Answer 15

Only one abnormal copy of the paired gene is necessary to manifest the disease.

Question 16

Give four examples of autosomal dominant diseases.

Answer 16

Neurofibromatosis: defective gene on Ch. 17, multiple nerve sheath tumour.

Polycystic kidney disease: mutations in PKD-1 gene on Ch. 16.

Familial hypercholestremia.

Marfan syndrome: fibrillin-1 gene mutation on Ch. 15. It is disorder of connective tissue, long limbs, long figures, defect in heart and aorta.

Question 17

Define autosomal recessive disease.

Answer 17

Both copies of the paired gene are required to be abnormal to manifest the disease.

Question 18

Define X-linked recessive.

Answer 18

X-linked diseases usually occur in males as they have only one X chromosome. Females can get an X-linked recessive disorder, but this is very rare. An abnormal gene on the X chromosome from each parent would be required, since a female has two X chromosomes.

Question 19

Give examples of X-linked recessive disorders.

Answer 19

Haemophilia A - it is a rare bleeding disorder in which the blood doesn’t clot normally.

Duchenne muscular dystrophy.

Question 20

Give examples of multifactorial (polygenic) inherited diseases which are the outcome of genes and environmental factors.

Answer 20

Diabetes, hypertension, asthma, atherosclerosis, cleft lip and palate.

Question 21

How many chromosomes are present for Turner syndrome?

Answer 21

45X. (Women that are not fully developed).

Question 22

How many chromosomes are present for klinefleter’s syndrome?

Answer 22

47XXY (men with womanly features such as boobs).

Question 23

What is Down syndrome?

Answer 23

Most common cause of intellectual disability (I.Q. ranges 25-70). Most individuals have an extra copy of a segment from chromosome 21.

Question 24

What are the signs and symptoms?

Answer 24

A shortening of all parts of the body.
A wide and flat face with a small nose.
Associations with congenital heart disease.
Increased risk for specific leukaemia and immunological deficiencies.
Mental retardation (similar to Alzheimer’s disease).
Protruding, big and wrinkled tongue.
Slanted eyes.

Question 25

How does bacteria cause illness through producing coagulase and streptokinase?

Answer 25

coagulase: clots blood, protects the bacteria from the immune system; but also prevents spread of the bacteria.
streptokinase: bacterial enzyme that dissolves blood cots, allowing bacteria to spread.

Question 26

What are the indications of someone having klinefleter’s syndrome?

Answer 26

Tall males, hypogonadism, infertility and impulsive behaviour.

Question 27

What are the symptoms for turners syndrome?

Answer 27

Tall girls, below average intelligence, gonadal function is normal but may have premature ovarian failure. Affected males have reduced IQ, prominent jaw and forehead.

Question 28

How does polyploidy arise?

Answer 28

From fertilisation by two sperm (dispermy) or fertilisation of diploid sperm and ovum because of an abnormality in their maturation divisions.

Question 29

Describe the structure of viruses.

Answer 29

Viral genome codes for important enzymes required for replication. Have a protein coat called a capsid made up of numerous capsomers. Some viruses contain a lipid outer envelope derived from the plasma membrane of the host cells acquired through budding. Protein spikes.

Question 30

Give an example of DNA viruses that are enveloped and naked.

Answer 30

Herpesvirus (enveloped)

Adenovirus (naked)

Question 31

Give an example of RNA viruses that are enveloped and naked.

Answer 31

Retroviruses (enveloped)

Picornaviruses (naked)

Question 32

How do viruses cause disease?

Answer 32

Cell lysis: shutting down synthesis of macromolecules, particularly polypeptides by the host cell, e.g. Adenoviruses.

Cell fusion: Virus-specified fusion proteins mediate the entry of certain viruses through the plasma membrane of the cell; they also cause the formation of multinucleated giant cells, e.g paramyxoviruses.

Transformation: incorporation of viral genes, e.g EBV.

Question 33

What is the TORCH complex?

Answer 33

Infection of a developing fetus or newborn by any of a group of infectious agents including toxoplasma, rubella virus, cytomegalovirus, herpes simplex virus.