Human biological science
Assignment 3
Yasmin Suhaib
1. Mutagen
A mutagen is a physical or chemical agent that changes the genetic material,
usually DNA, of an organism and thus increases the frequency of mutations
above the natural background level. As many mutations cause cancer, mutagens
are typically also carcinogens.
2.Two major types of mutations
i) Chromosomal error
a. Additions
An insertion is the addition of one or more nucleotide base pairs into a DNA
sequence. This can often happen in microsatellite regions due to the DNA
polymerase slipping. Insertions can be anywhere in size from one base pair
incorrectly inserted into a DNA sequence to a section of one chromosome
inserted into another.
On a chromosome level, an insertion refers to the insertion of a larger sequence
in to a chromosome. This can happen due to unequal crossover during meiosis.
b. Deletion
Deletions remove one or more nucleotides from the DNA. a deletion (also called
gene deletion, deficiency, or deletion mutation) is a mutation (a genetic
aberration) in which a part of a chromosome or a sequence of DNA is missing.
Deletion is the loss of genetic material. Any number of nucleotides can be
deleted, from a single base to an entire piece of chromosome.[1] Deletions can be
caused by errors in chromosomal crossover during meiosis. This causes several
serious genetic diseases.
Mutations that result in missing DNA are called deletions. These can be small,
such as the removal of just one "word," or longer deletions that affect a large
number of genes on the chromosome. Deletions can also cause frameshift
mutations. In this example, the deletion eliminated the word cat.
c.non-disjuction
Meiosis in which there is a failure of paired homologous chromosomes to
separate; results in an abnormal number of chromosomes in the daughter cells.
Nondisjunction is the failure of two members of a homologous pair of
chromosomes to separate during meiosis. It gives rise to gametes with a
chromosomal content that is different from the norm. The consequences of this
are usually quite severe, and a number of clinical conditions are the result of this
type of chromosome mutation.
ii) Error at the DNA level
There are many types of mutations that change not the protein itself but
where and how much of a protein is made. These types of changes in DNA
can result in proteins being made at the wrong time or in the wrong cell type.
Changes can also occur that result in too much or too little of the protein
being made.
Name of the
Cause/causes
Symptoms
Possible cures
Small stature
Physical therapy
Mental retardation
Speech therapy
Reduced muscle tone
Educational support,
Poor coordination
Social, Vocational and
medical services
condition
Chromosome Family history of
genetic disease
18 deletion
syndrome
Parents with a genetic
disease
Closely related
parents
Nystagmus
Parents who are
genetic disease
carriers
Conductive deafness
(Deletion of
chrosomes)
Small head
Various other symptomatic
and supportive measures
Seizures
Midfacial hypoplasia
Deep-set eyes
Carp-shaped mouth
Narrow palate
Tapered fingers
Emanuel
syndrome
Emanuel syndrome is
Severe mental retardation
caused by the presence
of extra genetic
microcephaly,
material from
chromosome 11 and
Failure to thrive,
chromosome 22 in
each cell.
Preauricular tag or sinus,
Ear anomalies, cleft or higharched palate,
micrognathia,
Kidney abnormalities,
Congenital heart defects,
Genital abnormalities in
males.
Chromosome analysis
FISH testing
Whole chromosome paint
(WCP)
Array genomic hybridization
(aGH)
3 alpha
methylglutaconicaciduria, type 3
Autosomal
recessive disorder
Degeneration of
optic nerves
Dopaminergic blockers
Haloperidol
X-linked disorder
Inability to maintain
posture
Pimozide
Poor muscle tone
Tetrabenazine
Involuntary
movements
Reserpine
Psychomotor delay
Metabolic acidosis
Muscle dystonia
Clonazepam
Error at DNA level
Decreased brain
function
Diazepam
Cognitive deficit
Phenytoin
Vision loss
Carbamazepine
Horizontal
nystagmus
Valproic acid
Chorea