Lecture 1

Question 1

Genetic disorders account for ….. of all:

childhood blindness, childhood deafness, severe MR

Answer 1

50%

Question 2

Genetic disorders / CA account for…. of all childhood hospital admissions

Answer 2

30%

Question 3

Genetic disorders / CA account for … of all childhood deaths

Answer 3

40-50%

Question 4

….. of the population (by age 25 years) have a disorder

in which genetic factors play a role

Answer 4

5 - 8%

Question 5

….. of all malignancy is directly due to genetic factors

Answer 5

1 %

Question 6

….. of common cancers have a strong genetic component

Answer 6

10 %

Question 7

Chromosome disorders

Answer 7

Loss of tiny amount of
chromosome material molecular cytogenetics (FISH),
microarray CGH.

Question 8

Age of expression of chromosomal disorders

Answer 8

1st trimester

Question 9

Age of expression of single gene disorders

Answer 9

At delivery but also LATE ONSET (20s/30s)?

Question 10

Single gene disorders that increase in adulthood (late onset) are …

Answer 10

Huntingtonschorea

myotonic dystrophy

Question 11

Genome

Answer 11

the totality of an organism`s DNA

Question 12

Human Genome

Answer 12

a set of instructions for construction and

management of human body

Question 13

Euchromatin

Answer 13

forms the main body of the
chromosome and has a relatively high density
of coding regions or genes.

Question 14

Heterochromatin is

Answer 14

chromatin that is either

devoid of genes or has inactive genes

Question 15

Heterochromatin eg..

Answer 15

Constitutive

Facultative (Barr body)

Question 16

how much of our DNA actually encodes

proteins

Answer 16

< 2%

Question 17

Special features of chromosomes

Answer 17

Euchromatin
Heterochromatin
Centromere
Telomeres

Question 18

Centromere

Answer 18

facilitate separation

Question 19

Telomeres

Answer 19

facilitate DNA replication

process

Question 20

House keeping genes

Answer 20

20% of genes
Transcribed in ALL cells of the body
Encode products required for cell MAINTENANCE AND METABOLISM

Question 21

Tissue – specific

genes)

Answer 21

80% of the genes 
Transcribed only in SPECIFIC TISSUES AT SPECIFIC TIME
In most cells only
a small proportion of genes are actively
transcribed even though all have exactly
the same DNA sequence.

Question 22

gene

Answer 22

Fundamental unit of heredity

Question 23

“Structural” gene

Answer 23

gene that codes for a
protein product Sequence of DNA that can be
translated to protein

Question 24

Single copy DNA

Answer 24

45% of genome

Question 25

Repetitive DNA

Answer 25

55% of genome

Question 26

Divisions of Repetitive DNA

Answer 26

Satellite and Dispersed DNA

Question 27

Satellite DNA

Answer 27

Alpha- tandem repeats in centromeres
Minisatellite- tandem repeats
Microsatellite- “

Question 28

Dispersed DNA

Answer 28

SINEs- short interspersed repeated sequences

LINEs- long repeated sequences

Question 29

Variation

Answer 29

a change in genetic

material

Question 30

Mutation

Answer 30

disease –causing
variation of a single gene (DNA
sequence) or chromosomes

Question 31

Alleles

Answer 31

the differing DNA

sequences among individuals

Question 32

Polymorphism

Answer 32

> 2 alleles,
each having a frequency that
exceed 1% of the population.
They can be normal variations or
rarely disease-causing alleles

Question 33

Gene size effect on mutation rates

Answer 33

• large genes are more likely

mutation hotspots - methylated CG to TG

Question 34

Mutations in genes can occur

because of

Answer 34

• DELETIONS
• INSERTIONS
• DUPLICATIONS
• SUBSTITUTIONS
• GENE FUSION
• AMPLIFICATIONS

Question 35

DELETIONS

Answer 35

• uncommon
• indicated by the
absence / altered
size of a DNA
fragment

Question 36

examples of DELETIONS

Answer 36

Thalassemia
Cystic Fibrosis 
DMD/BMD
Growth hormone deficiency
Familial hypercholesterolemia

Question 37

Alpha Thalassemia

Answer 37

The loss of 1 or 2 of
these genes has no
clinical effect
The loss of all 4
(Southeast Asians) leads
to hydrops fetalis
(stillbirth or neonatal
death)
The loss of 3 of these
genes leads to
moderately severe
anemia.

Question 38

DUPLICATIONS

Answer 38

Charcot-Marie-Tooth disease
type 1A
mis-pairing between
homologous DNA sequences
in close proximity

Question 39

INSERTIONS

Answer 39

Hemophilia -
insertion of a LINE in the
factor VIII gene
Neurofibromatosis -
insertion of an Alu ( SINE)
sequence

Question 40

SUBSTITUTIONS

Answer 40

most
common cause of
mutagenesis in the
human genome
Sickle cell anemia
Phenylketonuria
 Thallassemia

Question 41

Gene fusion

Answer 41

Hemoglobin
Lepore
Red / green
color blindness
Unequal
crossing over

Question 42

deuteranopia

Answer 42

) Unequal cross-over can produce a green dichromat with no green genes -

Question 43

red dichromat - protanopia or a green anomalous trichromat - deuteranomaly.
produced by..

Answer 43

Unequal cross-over that occurs within the red and green genes

Question 44

protanomaly

Answer 44

Cross-over within the red and green genes can also produce red anomalous
trichromats -

Question 45

AMPLIFICATIONS

expanded repeats

Answer 45

Increase in size of repeat
DNA sequences normally
present within or near
certain genes

Question 46

AMPLIFICATIONS eg…

Answer 46

Fragile X syndrome
Huntington disease
Muscular dystrophy
Friedreich ataxia

Question 47

Molecular Consequences of

Mutation

Answer 47

A Gain of Function of the protein product some
AD disorders.
A mutation resulting in a novel protein,
over-expression or inappropriate expression of a
protein such that there is an added or increased
function of the mutant protein
McCune-Albright syndrome
Charcot-Marie-Tooth disease;

Question 48

McCune - Albright syndrome

Answer 48

polyostotic fibrous dysplasia (bone lesions),
cafe au lait spots (skin lesions), and hyperfunction of several endocrine glands
(precocious puberty, hyperthyroidism,
pituitary gigantism, or Cushing’s syndrome)