Inherited Change
- Created by: AnneBoleyn1501
- Created on: 15-11-20 10:10
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- Inherited Change
- Studying inheritance
- Genotype
- Phenotype
- Homologous chromosomes
- Monohybrid inheritance
- Genetic crosses
- As per GCSE
- Gregor Mendel
- Study of inheritance in pea pod colour
- Law of segregation
- In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete
- 3:1
- Genetic crosses
- Probability and genetic crosses
- Actual results of genetic crosses rarely same a s predicted
- Each outcome due to chance
- Larger the sample, more likely actual results are to come near to theoretical
- Actual results of genetic crosses rarely same a s predicted
- Dihybrid inheritance
- When 2 characters determined by 2 different genes located on different chromosomes
- 9:3:3:1
- Law of independent assortment
- Each member of a pair of alleles may combine randomly with either of another pair
- Codominance and multiple alleles
- Codominance
- Both alleles are expressed in the phenotype
- Snapdragon flower colour
- 2:1:1
- Multiple alleles
- Human ABO blood groups
- When there's >2 alleles, of which only 2 may be present at the loci of an individual's homologous chromosomes
- Codominance
- Sex-linkage
- X and Y chromosomes are different shapes and sizes
- eg. haemophilia
- Much more common in males
- only need one defective X chromosome, females need two
- Females often die at start of menstruation
- Much more common in males
- Pedigree charts
- Square = male. Circle = female. Shaded = affected
- Autosomal linkage
- When two or more genes are carried on the same autosome
- 3:1
- Epistasis
- Arises when the allele of one gene affects or masks the expression of another in the phenotype
- eg. Albino. 9:4:3 in mice.
- If the pigment melanin isn't coded for, then the other alleles in the phenotype can't be expressed.
- Or where genes act in a sequence by determining the enzymes in a biochemical pathway. If one enzyme is non-functional another may not be expressed.
- Eugenics (1883 - 1940)
- Example of how genuine scientific research and knowledge can be interpreted wrongly and used for bad.
- Made famous by the Nazis, but all across Europe and the USA at the time there were many laws promoting eugenic values and racial cleansing.
- Chi-squared test
- (O-E)^2/E
- O = observed values
- E = expected values
- Degrees of freedom. Critical values
- If the value for chi-squared is greater than the critical value, then the results are statistically significant
- (O-E)^2/E
- Studying inheritance
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