Post on 21-Dec-2015
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)