Summary Topic 3 Genes

Genes and the environment



Cancer-uncontrolled cell division


radiation
ionising
-




UV ,
S.I units -

X-ray
~
Gamma
~

Carcinogens ; tobacco smoke , abestos



mutation involved in cell division


proto-oncogenes >
- stimulate cell division
cell
differention
>
-
stop

Proto-oncos
Oncogenes metal igi
a


Tumour supressor genes prevent tumour
formation
-




>
-
promote apoptosis



-Polygenic Inheritance when multiple
-




loci determine a
genes , found at

and different
therefore to
single
continuous
Phenotype
give rise

Variation


↳ can take value within a
a
range

Phenotype affected by
continuous
display variation
-

are

bote +
genes environment
polygenic
=




Discontinuous = discrete
categories