PS275 Lecture Notes - Lecture 3: Gamete, Intellectual Disability, Diethylstilbestrol
Document Summary
Each chromosome contains genes: made up of dna, the chemical code for development, shaped like a double helix, has the ability to replicate. After the sperm and egg meet, body cells begin to from by duplicating its chromosomes. Step 1: original parent cell (only 4 of the 23 chromosomes are shown here) Step 2: each chromosome splits lengthwise, producing a duplicate. Step 3: the duplicate chromosomes move to opposite ends of the parent which begins to divide. Step 4: the cell completes its division, producing two daughter cells that have identical sets of chromosomes. Meiosis is about sex cells: every human has germ cells, germ cells produce gametes (sperm for males, ova in females) Tep 1: ea(cid:272)h ger(cid:373) (cid:272)ell"s origi(cid:374)al (cid:272)hro(cid:373)oso(cid:373)es dupli(cid:272)ate itself. Step 2: crossing-over takes place among adjacent chromosomes to create a new hereditary combination. Step 3: the original cell divides to form 2 parent cells, each of which have 23 duplicated chromosomes.
