Mendal's Work Flashcards
What did mendals monohybrid crosses show
When pure breeding individuals (homozygous dominant) are bred with different pure breeding individuals (homozygous recessive), offspring will have dominant phenotype
What’s mendals ratio
3:1
3 ways mendals ratio may not always be achieved
Sample size may be too small
Fertilisation is random
May be a selection pressure that favours some alleles over others
What do dihybrid crosses show
How 2 characteristics, controlled by 2 different genes on different chromosomes are inherited
How many possible phenotype could a dihybrid cross produce
Why
4
As the genes that control e.g shape, colour are on different chromosomes
How could any gene for colour combine with any one of the shape genes
As during meiosis, the chromosomes line up randomly at the equator before splitting
How many letters does each organism have a genotype of
4 letter (lower + upper case)
What ratio were the results of mendals law of independent assortment very close to
The F2 generation ratio
9:3:3:1
What was mendals second law he created due to his findings
Each member of a pair of alleles may combine randomly with either of another pair (codominance)
E.g of mendals second law
Petal colouration in plants
1st allele - codes for an enzyme that catalyses a reaction causing 1 colour
2nd allele - codes for an altered enzyme that doesn’t catalyse reaction so no colour is made
In codominance crosses what do you have to use different letters to represent
The phenotypes
E.g of codominance cross
Blood groups
I is used to represent the gene for blood type (stands for immunoglobulin gene)
