1. Genetics in the Cell
cell membrane
nucleus
cytoplasm

2. 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

3. 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

4. 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

5. chromosomes are made of supercoiled DNA

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

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

10. 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

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

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