1. Polymorphism & Restriction Fragment Length Polymorphism (RFLP)

2. Genome Variation Definition:
In 2 non-related individuals: 0.1% genome variation (1 in each 1500 bases)
Polymorphism
Mutation
Clinical effect
Clinically harmless (No effect on phenotype
Potentially harmful (results in genetic disease
incidence
≥ 0.1%
rare:  0.1%

3. Polymorphism
Polymorphism: is a variation in nucleotide sequence from one individual to another, occurring in the non-coding regions of DNA.
RFLP: is a genetic variant that can be examined by cleaving the DNA into fragments (Restriction fragments) with a RE. The length of the restriction fragments is altered if the genetic variant alters the DNA so as to create or abolish a site of RE cleavage. It can be used to detect human genetic variations, e.g. in prospective parents or in fetal tissue
2 types of DNA variation result in RFLP:
SNP
VNTR
Considered markers, which, in most cases, have NO known effect on the structure or rate of production of any particular protein.

4. Single Nucleotide Polymorphism (SNP; 90% of human genome variation)

5. Variable Number of Tandem Repeats (VNTR)
short sequences of DNA at scattered locations in the genome
Repeated in tandem (one after another)
The # of these units varies from person to person, but is unique for any given individual
Serves as a molecular fingerprint

6. Variable Number of Tandem Repeats (VNTR)
VNTR loci: sites in genome that are frequently showing VNTR, important in DNA fingerprinting analysis (e.g. in forensic & paternity identity)

7. RFLP of VNTR

8. Prenatal Diagnosis Methods available:
It is recommended if there is a history of severe genetic disease, (affected previous child or near relative)
Its aim is to determine the presence of the disorder in a developing fetus
Methods available:
Visualization of the fetus e.g. by Ultrasound or fetoscopy:
If the genetic abnormality → gross anatomic defects e.g. neural tube defect
Amniotic fluid biochemical analysis:
e.g. level of a fetoprotein (increase in open neural tube defects, & low in Down syndrome.
Fetal cells in amniotic fluid or in chrorionic villi biopsy: Karyotyping: the morphology of the metaphase chromosomes (e.g trisomies, translocations →abnormal length of chromosome
Fetal DNA analysis: (the most detailed genetic picture; DNA from WBC, Amniotic fluid, or Chorionic villi
DNA has to be amplified first:
In the past: cell culture
Now: PCR

9. Examples of diseases diagnosed prenatally
Sickle cell anemia:
Could be diagnosed prenatally by:
I- Electrophoresis analysis of the amount & type of Hb obtained by hemolyzing fetal blood
1- risk in obtaining fetal blood
2- Late detection (2nd trimester)
2- Fetal DNA then do RFLP:
Advantages:
1- Safe
2- early detection

12. RFLP in a family with a child affected by PKU