Cells in most parts of the male body contain PAIRS of chromosomes.
Cells in most parts of the female body contain PAIRS of chromosomes.
Sperm cells produced in the testes contain UNPAIRED chromosomes.
Egg cells produced in the ovaries contain UNPAIRED chromosomes.
When the egg cell and the sperm cell fuse during fertilisation, the chromosomes form new pairs.
The cells in the baby’s body will contain chromosomes from both parents.
Fig. 6 The offspring from sexual reproduction have chromosomes from both parents. (Only two of the 23 pairs are shown in this diagram.)
12.2 Patterns of inheritance Genetically controlled characteristics
Activity Can you roll your tongue? The ability to roll your tongue is determined partly by genetics and is partly learned. See if you can roll your tongue. How many other people in your class can roll theirs?
Every individual organism within a species is unique. Even when two or more individuals are genetically identical, like twins can be, each one is still unique. This is because the characteristics of an individual are affected by both genetic factors and environmental factors. For example, your height is influenced by genetic factors but also by your diet, especially while you are growing up. Many species also teach skills to their offspring. Skills such as using tools and behaviours
such as avoiding predators can be taught. However, learning these skills and behaviours does not change a person’s genetic make-up. These skills cannot be passed on to the next generation through genes. They are not genetically controlled. It is sometimes difficult to determine whether a particular characteristic is genetically controlled or not.
