Lec. 20: Genes and Chromosomes 1: Mendel and the Gene Flashcards
Gene
A discrete unit of heriditary information consisting of a specific nucleotide seuquence in DNA
Character
An observable heritable feature
flower color, seed color, seed shape
Trait
any detectable variation in a genetic character
purple, yellow, round
What was the research method to show inheritance was discrete?
- removed stamens from purple flowers
- transferred sperm bearing pollen from white flower to egg bearing carpel of purple flower
- pollinated carpel matured into pod
- Planted seeds from pod
- Examined offspring (which were all purple flowers in F1 generation)
Principles of hereditary known as law of segregation and indepent assortment was a result of:
the quanitive analysis of results in the F2 GENERATION
Alleles
alternative forms of a gene
Locus
The position of a gene on a chromosome (Each gene has a specific locus)
Why do heterozygous offspring only produce its dominant trait?
The recessive trait has a different sequence that doesn’t code for a protein or an enzyme (ie lack of white pigment enzyme)
Mendel’s law of segregation
The two alleles for each character segregate (seperate) into different gametes.
Homologous chromosomes (alleles) seperate in Anaphase I
ALLELES FROM MOTHER SEGREGATE WITH ALLELES FROM FATHER
Mendel’s Law of Independent Assortment
Each pair of alleles segregates independently of other pairs during gamete formation
Test Cross
An unknown genotype (dominant phenotype) will cross with a recessive phenotype/genotype to determine the unknown genotype
Multiplication Rule
When trying to calculate the probability of a single genetic event
Addition Rule
When trying to calculate probability of more than one mutually exclusive genetic event
When does independent assortment not hold true?
When 2 characters are on the same chromosome
