### occurrence:

Point mutation
* affect individual genes, whereas chromosomal alterations affect many genes.
* are particularly important for oral cancer development
  - single-base changes in a gene's DNA sequence
* are the rarest form of mutation
  - result of the substitution of a single base
* can have a significant impact on phenotype, as in the case of sickle-cell disease
  - result from errors in DNA replication or from environmental effects
* change a nucleotide single base pair.
* changes a single nucleotide and therefore changes a single specific codon.
* involve substitution of one or a few bases through replication errors.
* occur before and during DNA replication
  - when a single base pair of a gene is changed
* result in the substitution of one amino acid for another.
+ Genetic engineering
  * Gene targeting is a different technique which uses recombination to change a gene. It can be used to delete a gene, remove exons, add a gene, or introduce mutations. Point mutations change a nucleotide single base pair.

Repeat
* are sequences that appear two or more times in the target molecule.
* is an occurrence
  - used in the military to fire another salvo of artillery

### occurrence:

Retardation
* allows for concrete to be moved on barges or pumped a long distance without setting.
* can vary from mild to very severe.
* causes the mean chemical velocity to be slower than the groundwater velocity.
  - delays
  - one of the hardest issues for parents to deal with
  - stupidity
* linked to environmental deprivation is called a.
* major social, educational and health problem in America today.
* occurs along the plane of an electric voltage applied across the liquid crystals.
* serious disability that some people and families have to deal with.

### occurrence | retardation:

Growth retardation
* common sign in children.
* continues after birth as failure to thrive.
* is evident in length, weight, and head circumference
  - present in some patients who have an early onset of disease

### occurrence | retardation:

Mental retardation
* affects each individual differently
  - families of every social and economic level
  - people in different ways
* becomes evident as infants begin to miss their normal developmental milestones.
* can affect any family
  - result from cerebral hemorrhage, as can spastic paralysis
* causes permanent damage.
* condition of sub-normal intellectual and social development.
* contagious disease.
* cuts across racial, ethnic and socio-economic lines
  - ethnic, educational, social and economic backgrounds
* euphemism for low intelligence.
* feature of many genetic syndromes.
* has borders with many other diseases
  - many possible causes
* involves global delays and generally affects all areas of functioning.
* is associated with a variety of deprivations
  - the disorder
  - caused in hundreds of ways
* is characterized by a complex set of behaviors with a myriad of manifestations
  - delayed pattern of development
  - chronic conditions
* is common and often progressive
  - but normal intelligence occurs in some cases
  - common, as is hyperactivity, extreme nervousness, and poor attention span
  - developmental delays
  - exacerbated by infections
* is found among all races and cultures
  - in persons of all ages, races, cultures and economic conditions
  - frequently present
* is just one developmental disability
  - of any number of developmental disabilities
  - nonprogressive
  - one among a vast array of disabilities
  - synonymous with mental deficiency
* is the common denominator
  - most common developmental disability
* life-long problem with multiple causes and manifestations.
* mental disability distinct from mental illness.
* permanent condition.
* ranges from mild to severe.
* refers to a person's capability to think and reason
  - substantial limitations in present functioning
* severe and chronic disability.
* varies widely, from minimal to severe.