Karyotypes and Pedigrees Genetics and Chromosomal Analysis Karyotypes and Pedigrees

Chromosomal Analysis There are various ways to analyze chromosomes: 1. Karyotypes 2. Chromosome painting 3. Gel electrophoresis (DNA fingerprinting)

Chromosome painting: using fluorescents to compare chromosomes

Gel Electrophoresis: separating DNA according to their molecular size

Karyotype- a chart of chromosomes pairs

Male Karyotype

Any individual with at least one Y chromosome is male and without one Y is female. XX- Female XY –Male

Down Syndrome (trisomy-21) Autosomal nondisjunction affected individuals survive to adulthood It occurs in about 1 and 700 live births

- There is a third chromosome on the 21st pair. - They have varying degrees of mental disability. - The incidence is higher among older mothers, especially those over 40.

Characteristics: short, slanted eyes, thick tongue

SEX CHROMOSOME NONDISJUNCTION – Unusual numbers of sex chromosomes

One X chromosome is missing Turner’s Syndrome XO One X chromosome is missing FEMALES ONLY! Monosomy X – gets only ONE X chromosome Sterile female Low intelligence No breasts (no secondary sex characteristics)

Klinefelter syndrome XXY Extra X chromosome MALES ONLY! causes a male to be sterile No beard, no deep voice, no masculine muscle tone (no secondary sex characteristics)

Most of these individuals lead normal lives, but they can not have children and some may have some degree of mental retardation.

Superman Syndrome XYY Male Has an extra Y chromosome On average 3” taller than your average male Clinical phenotype of this syndrome is normal

RECESSIVE AUTOSOMAL DISORDERS-Deals with chromosome pairs #1-22

Cystic Fibrosis Excess mucus in lungs Mostly found in Caucasian population Chromosome #7

Phenylketonuria (PKU) Lack of normal skin pigmentation Mental retardation Can prevent with special diet Chromosome #12 Absence of certain enzyme Damage to Central Nervous System

Tay-Sachs Disease Lipids (fats) in brain cells Affects Central Nervous System Mental deficiency Fatal, usually causes death by age 2 Mostly in Jewish population Chromosome #15

DOMINANT AUTOSOMAL DISORDERS - Deals with chromosome pairs #1-22

Huntington’s Disease Chromosome #4 Memory loss Uncontrolled movements Onset occurs between the ages of 30-50 (middle age) Forgets things, stumbles Cause: abnormal repeating of certain bases

CODOMINANT AUTOSOMAL DISORDERS

Sickle Cell Anemia Sickle-shaped red blood cells Difficulty breathing Nitrogen base is changed, affects HEMOGLOBIN that carries oxygen Mostly in African Americans Cells clot Capillaries are cut causing bleeding internally. Chromosome #11

Pedigree- a graphic representation of genetic inheritance from generation to generation

Pedigree Symbols Normal female Affected female Carrier/heterozygous female Normal male Affected male Carrier/heterozygous male Death Married Parent and Offspring

A carrier is represented by a half shaded circle or square A carrier is represented by a half shaded circle or square. They are heterozygous- they have a recessive gene but it does not show.

DNA FINGERPRINTING aka GEL ELECTROPHORESIS

Why ?? To determine whether suspects have been at a crime scene/location Who?? Law enforcement

How does it work??? Small DNA samples can be obtained from blood, hair, skin, and copied millions of times. The DNA is cut into fragments of different lengths DNA fragments can then be separated by electrophoresis, and compared with those obtained from a crime scene

The genes follow standard patterns from person to person BUT the non-coding segments produce distinct combinations of patterns that are unique to each individual SO unique fingerprints can be used to identify a single person.

No two people have the same DNA (except identical twins)