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Molecules and cells
genetics
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Created by
liya t
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Cards (12)
Aims of Medical
Genetics
Understand the genetic basis and molecular
pathology
of
inherited
disease
Laboratory
diagnostic services
Provide
risk
calculation
,
diagnosis
&
counselling
, etc
Work towards a
cure
/
better
management for
inherited diseases
Genes and chromosomes
Chr
1
: ~
2,047
protein-coding genes
Chr
21
: ~
231
protein-coding genes
Each chromosome is a long
double-stranded
DNA molecule
,
coated
with
proteins
DNA =
deoxyribonucleic acid
Patterns of Inheritance
Chromosomal
Single gene disorder
:
Autosomal dominant
,
Autosomal recessive
,
X-linked recessive
, (X-linked dominant)
Multiple genes
+
environmental factors
(
multifactorial
)
Multiple genes +/- chromosomal abnormalities
(cumulative genetic)
Extra chromosome 18-
Edwards syndrome
Mendelian-
single gene disorder
Variable expressivity
- People affected at different extends by same disorder
Dominant or recessive inheritance?
Dominant
- only need
one
faulty gene
to get
disease
Often: "
Variable expressivity
"
Dominant or recessive inheritance?
Features:
Vertical
or
Horizontal
Pattern
Horizontal
: People in
single
generation affected
linked or autosomal inheritance?
Features:
Male
to
male
transmission
Mode of inheritance:
Autosomal
(because a man passes on
Y
(not his
X
) chromosome to
sons
)
Knight's move inheritance
Features: Two
males
related through
unaffected female
Only
males
affected
Mode of inheritance:
X-linked recessive
(the female has an additional
unaffected X
chromosome which
'protects'
her)
Effects of genetic variants
Complete inactivation of function (e.g.
deletions
;
premature translation stop
)
Decreased
function (e.g. amino acid
substitutions
in key regions, regulatory variants)
No significant effect (e.g.
non-coding DNA,
no change in
amino acid
, alters
less
important region of protein)
Increased
or changed function (e.g.
amino acid
substitutions in key regions,
regulatory
variants,
duplications
)
Variants & inherited disease
Disease or condition can occur in all people with a particular
variant
in
1
gene copy (e.g.
achondroplasia
–
dominant
mutation)
Some variants may cause disease only when both copies of the
same
gene are affected (e.g.
cystic fibrosis
-
recessive
)
Cystic fibrosis
Affects
children and young adults
Affects
digestion
and
respiratory
system
Affects
males and females
Horizontal
pattern
Autosomal recessive
inheritance
Normal way gene switched on
RNA polymerase
carries out
mRNA
Protein
made in
ribosomes
Chain of
amino acids
-
polypeptide
Gene- made of
exons and introns
, exons
kept
and
introns
removed
Always start with
methionine
-
start codon