Chapter 1 Flashcards
Who is Gregor Mendel and what he discovered?
Gregor Mendel is the “father of modern genetics”, who discovered the principles of inheritance through his work on pea plants
What are the 7 antagonistic pairs of traits in peas that Mendel studied?
What is the Monohybrid cross?
It’s a one factor cross between parents that differ in only one trait, which is controlled by only one gene.
What Mendel revealed through the monohybrid cross?
Mendel revealed the units of inheritance (2 per individual) and the law of segregation
What is the Dihybrid cross?
It’s a two factor cross between parents that differ in 2 observed traits that are controlled by two distinct genes (color: green/yellow and shape: round/wrinkled)
What Mendel revealed through the dihybrid cross?
Revealed the law of independent assortment
What are the 4 Mendel’s postulates?
- Unit factors in pairs
- Principle of Dominance / Recessiveness
- Law of Segregation
- Law of Independent Assortment
What means “unit factors in pairs” postulate?
A unit factor is the trait (tall gene or dwarf gene), which inherits one allele from the mother and the other allele from the father (2 alleles together one gene)
What is the Principle of Dominance / Recessiveness?
In the pair of unit factors (alleles) for a single trait (phenotype) in a single individual, one unit factor (allele) is dominant to the other allele, which is recessive.
What is the Law of Segregation?
The two alleles for each trait separate (segregate) during gamete formation.
One gamete from each parent (total 2 gametes) unite at random at fertilization. For example, there is an equal probability that each gamete will receive either the tall unit factor or the dwarf unit factor.
What is the Law of Independent Assortment?
The law that states that each allele segregates into gametes independently of all other alleles in meiosis during gamete formation (producing genes)
- Y is just as likely to assort with R as it is with r
- y is just as likely to assort with R as it is with r
In the Monohybrid cross, each F1 hybrid produces 2 kinds of gametes in a 1:1 ratio. What are the expected genotype/phenotype ratios for the F2 progeny?
1: 2:1 ratio of genotypes and
3: 1 ratio of phenotypes
In the Dihyrbid cross, each F1 hybrid produces 4 kinds of
gametes in a 1:1:1:1 ratio. What is the expected phenotype ratio for the F2?
9:3:3:1 ratio of phenotypes
What is the Trihybrid cross?
It is the cross between the two individuals, which have 3 different genes that produce 3 or more traits corresponding to each gene. A gene (genotype) will determine a trait (phenotype)
What is the Fork Line Method/ Branch Diagram?
It’s the method, which breaks down multihybrid crosses into independent assorting monohybrid crosses that determine the
likelihood of each possible phenotype.