3.34 Causes of Mutation

1. A mutation is a change in the base sequence in the gene. 
2. Mutations could be caused by ionising radiations such as x-rays. 
3. It could be caused by sunshine- ultraviolet rays- skin cancer 
4. mutations could be caused by chemicals such as tars and tabacco- causes cancer
5. They cause mutation within the base sequence 
6. Chemicals which cause mutations are called mutigens, they also cause cancer. 

3.33 Antibiotic resistance

1. Staphlococcus aureus-bacteria which causes skin infection and some lung infection. 
2. Those who are affected by this bacteria can be treated by an antibiotic known as methecilline. 
3. This antibiotic kills the staphlococcus aureus. 
4. The type of staphlococcus aureus which can be killed by the antibiotic are known as susceptible form (mssa)
5. When a random mutation occurs within the genome of the staphlococcus aureus, the methecilline fails to kill it. This form is known as the resistant form of staphlococcus aureus. (mrsa)
6. The mutation has created genes within the bacteria has allowed it to break down the antibiotic. 

3.32 Types of mutation

1. The process of mutation produces new alleles. 
2. Alleles are responsible for the phenotype. 
3. their impacts could be beneficial or harmful or neautral 
4. the neutrality does not stay forever, it could change to beneficial or harmful due to environmental changes. 

3.30 mutation

3.29 Species Variation

1. Variations- differences we can see in the phenotypes of each individual. 
2. It is possible to count/measure these differences and show them through graphs. 
3. The phenotype depends on the genotype of each individual which is modified according to the environment. 
4. Variation in population is a variation within all these individuals. 
5. The difference in appearance within different species occur because all those individuals have different genotypes and they survive in different environments. 

1. Phenotypic variation in a population or species is due to environmental variation. E.g. the home language you speak.
   

3.21b Genetic Probabilities

1. f1 offspring cross with an f1 offspring. 
2. The parent phenotype is red petal crossed with red petal 
3. The parent genotype- Rr x Rr
4. Both parents are heterozygous. 
5. Meiosis takes place and the allele has to be separated, one into each type of gamete. 
6. In this case, there is a 50% chance that the pollen grain is carrying a R allele and there's a 50% chance that the pollen grain is carrying an r allele. 
7. Random fertilization occurs, as shown in the table, to be observed in the image. 
8. The probabilities depend on which pollen grain (R or r) fertilizes with which ovule (R or r)

3.21a Genetic probabilities

1. We're predicting the probabilities of offspring through monohybrid crosses. 
2. Monohybrid crossing- crossing which consists of only one gene. 
3. Let's consider the cross between a red petal plant and a white petal plant. 
4. The genotype of the red petal plant is RR and the genotype for a white petal plant is rr. 
5. This makes the R>r. In other words, red is dominant to white. 
6. The next stage involves meiosis which includes the production of the pollen grains and the ovules. 
7. The gamete will contain only one of the two alleles. 
8. For instance, in the production of the pollen, 1/2 the gametes will have the R and the other half will have the other big R as its an equal chance. 
9. In the production of the ovules we need to separate the alleles so that we only have 1 of the pair of alleles in each gamete. half of the ovules would have little r and the other half would have little r. 
10. Then we consider random fertilization. 

3.20b Pedigree 2

1. We are trying to figure out whether if the affected condition within the individual is caused by the dominant or the recessive allele. 
2. If it's caused by the recessive allele it will have the genotype dd
3. If it's caused by the dominant allele it will either have the genotype Dd or DD. 
4. The affected condition is caused through the recessive allele as shown in the example in the diagram. 

3.20a Family pedigree

1. If you had inherited a condition the circle would be filled in if you were female and the square would be filled in if you were male. 
2. These are often diseases but not always. 
3. The circle and squares represent phenotypes therefore these could be observed
4. the pedigree diagram shows that the female is affected yet the male is not. However, the child has not inherited the condition. 
5. The rest of the details can be observed in the diagram itself

3.18c

Allele key:

• B-blue petals
• W-white petals

1. The blue petal plant has a genotype of BB-two alleles 
2. The White petal plat has a genotype of WW-two alleles
3. If we cross the blue petal plant with the white petal plant we get an orange petal plant. 
4. We have an unusual third phenotype which is orange. This is known as the co-dominant.  
5. In the codominance both alelles the B and the W contribute to the phenotype.