Genetics

• Conception: ovum and sperm fuse to create zygote

• Chromosomes: contain all biologically inherited information (DNA)

• Ovum: 23 chromosomes (mom’s contribution)

• Sperm: 23 chromosomes (dad’s contribution)

Zygote

• 46 chromosomes (23 pairs: 23 from mom and 23 from dad)

• 22 pairs are called autosomes

• 23rd pair contain the sex chromosomes

Karotype

Mitosis

• Cell division resulting in new diploid cells (46 chromosomes)

• Chromosomes replicate, then split into two diploid cells

MitosisMitosis

Body CellBody Cell46 46

ChromosomesChromosomes

Daughter CellDaughter Cell46 46

ChromosomesChromosomes

Daughter CellDaughter Cell46 46

ChromosomesChromosomes

Meiosis

• Cell division resulting in haploid (23 chromosomes) cells

• Creation of gametes (sex cells: ovum and sperm)

Meiosis

Germ CellGerm Cell46 46

ChromosomesChromosomes

GameteGamete23 23

ChromosomesChromosomes

GameteGamete23 23

ChromosomesChromosomes

Polygenic Inheritance

• Affected by many genes rather than by a single pair.

Sex-linked Chromosomal Abnormalities

• Kleinfelter’s syndrome: XXY

• XYY syndrome

• Fragile X

• XXX

• Turner’s syndrome

Non Sex-linked Chromosomal Abnormalities

• Down Syndrome (Trisomy 21)– Translocation trisomy– Mosaicism– Nondisjunction during meiosis

Down Syndrome

Simian Crease

Maternal Age – Chromosomal Abnormalities

• Age Trisomy 21 rate Other chromosomal rate• 20 1/1667 1/526• 25 1/1250 1/476• 30 1/952 1/385• 35 1/378 1/192• 40 1/106 1/66• 45 1/30 1/21

Genetic Disorders

• TaySachs (autosomal recessive)

• Cystic Fibrosis (autosomal recessive)

• Phenylketonuria (PKU) (recessive)

• Muscular Dystrophy (dominant)