Genetics in the Cell cell membrane nucleus cytoplasm

In the nucleus of a cell: chromosomes – made of many different genes genes – hold the genetic information for each trait All the body cells of humans have 46 chromosomes

meiosis is the process used to make gametes (sex cells) gametes have ½ the # of chromosomes in the body cells Human gametes have 23 chromosomes

chromosomes in body cells chromosomes in gametes organism chromosomes in body cells chromosomes in gametes human 23 46 78 39 chicken goldfish 104 52 ant 1 2 corn 20 10 Horsetail fern 210 105 butterfly 380 190 chimpanzee 48 24

chromosomes are made of supercoiled DNA

DNA (DeoxyriboNucleic Acid) structure discovered in 1953 by James Watson and Francis Crick Watson, Crick and Maurice Wilkins won the Nobel Prize in 1962

DNA is shaped like a double helix (a twisted ladder) sides – alternating molecules of sugar (deoxyribose) and phosphate

A T T A A T G C C G A T A T G C A T C G G C Adenine (A) Thymine (T) rungs – four types of nitrogen bases: T A A T Adenine (A) G C always bond Thymine (T) C G A T Guanine (G) always bond A T Cytosine (C) G C A T C G G C

nitrogen bases are attached with hydrogen bonds nitrogen bases attach to sugars (deoxyriboses) not phosphates nitrogen bases are attached with hydrogen bonds A -- T

DNA is made of units called nucleotides. and so on… Each nucleotide has a sugar, a phosphate and a nitrogen base. (deoxyribose)