3.30 Mutation

- DNA, the base sequence (ACT) constitutes the Gene and the form of the Gene is called the Allele
- Certain processes can result in the change of the base sequence (into AAT).
- This change creates a new version of the allele
- It is possible that it will result into the production of an entirely different protein and have an entirely different effect on the phenotype.
- Different alleles (dominant and recessive) exist because of the process mutation = changes the base sequence of the gene.

3.29 Species Variation

- Variation = differences that we can see in the phenotype of individuals. Possible to count/measure these differences in graphic form.
- Individual: Phenotype = Gene + Environment
- Variation: V(population) = V(genorype) + V(environment)
1. Variation in population entirely due to Variation in Genotypes. (e.g. Blood groups) - Discontinuous
2. Variation in population/species due to Variation in Genotype and are modified by the environment to form the distribution curve (e.g. height of individuals) - Continuous
3. Variation in population entirely due to the environmental variation. (e.g. Home language). Cannot be inherited.

3.21b Genetic Probabilities

Parent Phenotype:
Red petal x Red petal

Parent Genotype:
Rr x Rr (both parents are heterozygotes)

Meiosis:
The alleles need to be separated one into each type of gamete.
1/2R, 1/2r (50 percent chance that the pollen grain will carry each of these)

Random Fertilization

Genotypes of the offspring:
RR : 2 Rr : rr

Phenotype ratio:
Red : Red : White, 1 : 2 : 1
- There is a 3 : 1 ratio (Red : White)(75% : 25%)(3/4 : 1/4)

These are probabilities, it depends which pollen grain fertilizes which ovule.

3.21a Genetic Probabilities

Parents:
Red Petals x White Petals

Genotype:
RR x rr (R>r, Red > White)

The next stage involves meiosis. The gamete will contain only one of the two alleles but it is an equal chance. 1/2 R or 1/2R x 1/2r x /2r

Random fertilization:
Drawing a table to illustrate the possible fertilizations that can occur between the pollen grains and the ovule.

Genotype of the offspring: ALL Rr,

Phenotype of offspring: all Red

Probability of Red x White = 100% Red Petaled flower.

3.20b Pedigree 2

3.20a Pedigree Diagrams

3.18c Codominance

Blue petal plant(B- has a genotype of BB) + White petal plant(W- has a genotype of WW) --- cross ---> Orange petal plant (unusual third phenotype which is orange)

Work out the genotype of the third phenotype:
When the blue petal plant reproduces with the white petal plant, it contributes one allele each. The heterozygote must be BW but generates a third, different distinct phenotype = CO-DOMINANCE

Both alleles B and W contribute to the phenotype and gives off the orange colour in this case.