Mendelian Genetics Flashcards
What’s a true-breeding strain (in Mendel’s experiences) ?
Strains in which each trait appeared unchanged generation after generation in self-fertilizing peas.
Explain the link between genotype and phenotype in a diploid organism
Genotype predicts the phenotype through dominant and recessive alleles. These different alleles will result in a DNA sequence that codes for certains enzymes/proteins that affect the phenotype.
What is a monohybrid cross ?
Mating between 2 organisms with 2 different alleles at a given locus of interest
What are Mendel’s 3 postulates ?
- Genetic characters are controlled by unit factors existing in pairs in individual organisms
- When two unlike unit factors responsible for a single character are present in a single individual , one unit factor is dominant and the other is recessive (only the dominant factor is visible)
- During the formation of gametes, the paired unit factors segragate randomly
True or false : the production of gametes are independant events.
True
What is a testcross ?
Cross between an individual whose genotype at one (or more) loci may be unknown and an individual who is homozygous recessive for the gene or genes in question
What are testcross used for ?
To determine the genoype of the unknown organism by crossing it with a homozygous recessive
What is a dihybrid cross ?
Mating between 2 organisms with 2 different alleles at 2 given loci of interest
difference between dependent and independent assortment ?
Dependent : if both genes are located closely on the chromosome, they will be inherited together
Independant assortement : the traits are inhered independetely
How does dependent assortment affect the phenotype probability ?
If a dihybrid cross has dependent assortement, the different phenotypic probabilities will be the same as in a monohybrid cross (because both genes are inhereted together)
explain the product law
The probability of 2 or more independent events occuring simultaneously is equal to the product of their individual probabilities
Ex: probability of a pea being round and yellow = (probability of being round) x (probability of being yellow)
What is Mendel’s fourth postulate ?
during gamete formation, segregating pairs of unit factors assort independetly of each other.
What is a trihybrid cross ?
Mating between 2 organisms with 3 different alleles at 3 given loci
What is the relation between the number of loci and the phenotypic variation of a trait ?
As the number of loci increases, the phenotypic variations are more and more subtle (closer and closer to being truly continuous)
how many genes affect skin colour ?
378
