1. Bellwork: Design an experiment to determine whether pink flowers on petunia plants result from incomplete dominance

2. Other patterns of inheritance
Section 11.3

3. Mendel’s work is not infallible
Life is not always so simple
Many genes have more than two alleles
Many traits are controlled by more than one gene
Incomplete dominance – some alleles are neither dominant or recessive
Phenotype lies between two end members
Example – flower color in some plants
Codominance – Phenotypes from both alleles are expressed
Possible to get black and white feathered chickens
Seen in humans with proteins that control cholesterol

4. Multiple alleles
Many genes exist in several forms and have multiple alleles
A gene with more than 2 has multiple alleles
Individuals still only have 2 copies of the genes
Human blood type – great example (page 320)

5. Polygenic traits
Many traits are produced by the interaction of several genes
Polygenic = many genes
Wide range of phenotypes
Example – human skin colour

6. Genes and the environment
Environmental conditions can effect gene expressions and influence genetically determined traits
Phenotype is not just determined by genes
Can you think of any examples in nature of how the environment can affect phenotype?

7. Meiosis
Section 11.4

8. How many sets of genes are found in most adult organisms?
Homologous – chromosomes from the male parent have a corresponding chromosome from the female parent
Diploid (2n) – contains two complete sets of inherited chromosomes and two complete sets of genes
Haploid (n)– only a single set of chromosomes, and a single set of genes
Gametes are haploid
How many chromosomes do humans have?

9. Phases of meiosis

10. Comparing mitosis to meiosis
Mitosis – a form of asexual reproduction
Daughter cells receive complete genetic copy
Meiosis – early stage of sexual reproduction
Alleles are segregated
Chromosome number halved

11. Gene linkage Each chromosome is a group of linked genes
Independent assortment holds true BUT chromosomes assort independently, not individual genes
Mendel missed it, because by luck or design, several of the studied genes were on different chromosomes, or were far apart

12. Gene mapping
The further apart genes are on a chromosome, the more likely crossing over will occur
The closer together the less likely they are to cross over
Possible to work out where exactly on the chromosome a gene is