Genetics in the Cellcell membrane

nucleuscytoplasm

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

organism chromosomes in body cells

chromosomes in gametes

human

chickengoldfish

antcorn

Horsetail fernbutterfly

chimpanzee

4678104

220

210380

48

2339521

1010519024

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 sugarand phosphate

(deoxyribose)

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

always bond

always bond

ATAGCTTGACG

TATCGAACTGC

nitrogen bases attach to sugars (deoxyriboses) not phosphates

nitrogen bases are attached with hydrogen bonds

A -- T

DNA is made of units called nucleotides.

Each nucleotide has a sugar, a phosphate and a nitrogen base.

(deoxyribose)

and so on…