Genes & Inheritance
By:
Miss Winda Rahma
7.1. Chromosomes, Genes, DNA
Chromosomes
Genes
DNA
üChromosomes are made of a chemical
substance called DNA;
üEach chromosomes is one enormously long
molecule of DNA;
üThis means that genes are also made of DNA.
7.2. Gametes and Inheritance
Gametes
Fertilisation
Inheritance
• Inheritance means passing on DNA (as chromosomes
containing genes) from parents to offspring;
• A baby’s sex is determined because a baby inherits X or Y
chromosomes from its parents. We can use the term sex
inheritance to describe this;
• All organisms also inherit other features from their parents. You
will find out more about this in the next topic.
7.3. Variation
Variation within a species
DNA and Variation
Environment and Variation
7.4. Natural Selection
You can summarise the theory like this:
1. In every species, there is variation among individual organism;
2. Some of this variation is caused by differences in their genes;
3. Some individuals have features that make it more likely that they will survive
than individuals that don’t have these features;
4. The individuals with these advantageous features are therefore more likely to
reproduce and pass on the genes that produce the advantageous features to
their offspring;
5. Over many generations, the genes that produce these advantageous features
get a little bit more common and the genes that are not so useful get a little bit
less common.
Bacteria and Antibiotics