Dominant and recessive inheritance

1
Dominant and recessive inheritance
Every person receives a pair of alleles(paired
genes either alike or different that affect a
trait) one from each parent. Dominant
inheritance A child receives contradictory
alleles and only the dominant one is
expressed. Heterozygous possessing different
alleles for a trait. Eg- curly hair and straight
hair.
2
Dominant and recessive inheritance
Recessive inheritance A child receives identical
recessive alleles resulting in expression of a
non dominant trait. Homozygous possessing two
identical alleles for a trait. Eg- tongue curling
ability from both parent, hence the child can
also be a tongue curler.
3
Multi factorial transmission
Combination of genetic and environmental factors
to produce certain complex traits. Phenotype
observable characteristics of a person. Eg
physical appearance. Genotype genetic makeup of
a person containing both expressed and un
expressed characteristics.
4
Mutations

• Mutations may be defined as changes in DNA
  sequence of cells genome and are caused by
  radiation, viruses, and mutagenic chemicals.
• Mutations in DNA can happen in two processes
• DNA damage from environmental agents such as
  ultraviolet light, nuclear radiation, or certain
  chemicals
• Mistake that occur when the cell copies its DNA
  in preparation for cell division.

5
Birth defects
PKU (phenylketonuria) This is a metabolic
disorder resulting in mental retardation. Treatmen
t Special diet begun in first weeks of life can
off set mental retardation.
6
Birth defects
Sickle-cell Anemia Deformed, fragile red blood
cells that can harm the blood vessels. Symptoms
include severe pain, stunted growth, frequent
infections, leg ulsers, prone to pneumonia and
stroke. Treatment pain killers, transfusion for
Anemia and to prevent stroke, antibiotics for
infections.
7
Birth defects
Tay-sachs disease Degenerative disease of the
brain and nerve cells, resulting in death before
age 5 No treatment, its only high in Eastern
Europian jews.
8
Sex chromosome abnormalities
Xyy - this syndrome is high among male child,
tall structure, tendency for low IQ especially
verbal, The frequency is high among one in
thousand birth. Treatment No special treatment.
9
Sex chromosome abnormalities
XXX(triple X) this is high among female, normal
appearance, menstrual irregulaties, learning
disorders, mental retardation. This happens one
in every thousand birth. Treatment Special
education
10
Sex chromosome abnormalities)
XXY(kleinfelter) this is seen among male child,
under developed secondary sexual characteristics,
small testicles, learning disorders. One in
thousand birth Treatment Hormone therapy and
special education.
11
Sex chromosome abnormalities)
XO (turner) this is highly seen in female, short
shoulder, webbed neck, impaired special ability,
no menstruation, inferiority, under developed sex
organs, incomplete development of secondary
sexual characteristics. This is seen one in every
thousand birth Treatment Hormone therapy and
special education.
12
Sex chromosome abnormalities)
Fragile x syndrome minor to severe mental
retardation, symptoms are high in males, this
will include delayed speech and motor function,
speech impairment and hyperactivity. One in every
Two thousand birth in female and one in every one
thousand two hundred birth in male. Treatment Educ
ation and behavioural therapy when needed.
13
Down syndrome
It is a chromosomal disorder characterized by
moderate to severe mental retardation. It is also
known as trisomy, this is caused by an extra
twenty first chromosome. This is high among older
parents. Treatment