Chapter 9 Patterns Of inherintance Part 1 Flashcards
Gene
Definition: region of DNA that contains information about a specific trait.
Example: Flower Color
Allele
Definition: a version of a gene
Example: Purple or Yellow
Heterozygous
Definition: Having two different alleles for a particular trait.
Example: Pp
Homozygous
Definition: Having two identical alleles for a particular trait.
Example: PP or pp
Genotype
Definition: The actual allele combination that is present on the chromosome.
Example: PP, Pp or pp
Phenotype
Definition: The physical characteristic that can be detected.
What the actual visible trait is.
Example: Purple Kernel or Yellow Kernel
Dominant
Definition: The allele that is expressed in a heterozygote (written as an uppercase letter)
Example: Purple (P)
Recessive
Definition: The allele that is not expressed in a heterozygote (written as a lowercase letter)
Example: Yellow (p)
Heredity
The transmission of traits from one generation to the next.
Genetics
The scientific study of heredity.
Gregor Mendel
Began the field of genetics in the 1860s
Deduced the principles of genetics by breeding garden peas
Relied upon a background of mathematics, physics, and chemistry
Character
A heritable feature that varies among individuals, such as flower color. Genes code for characters
Trait
Each variant of character. Eg purple or white flowers.
True breeding
When self fertilization produces offspring all identical to the parent.
Hybrids
Offspring of two different varieties are hybrids.
Cross fertilization
The fusion of male and female gametes (sex cells) from different individuals of the same species.
P generation
True-breeding parental plants
F1 generation
Hybrid offspring of the parental generation.
F2 Generation
Cross of F1 plants produces an F2 generation.
Monohybrid cross
A cross between two individuals in a single character is a monohybrid cross.
Eg. Plant with purple flowers x Plant with white flowers.
Cross between a plant with Purple Flowers and a Plant with Whote flowers.
The F1 generation produces all plants with Purple flowers.
A cross of F1 plants with each other produced an F2 generation with 3/4 purple and 1/4 white flowers.
Purple is a dominant trait and white is a recessive trait for the character of flower color in this particular plant.
Mendel’s 1st Law of Inheritance
Law of Dominance
states that in a heterozygous condition, the dominant expression of the trait will appear and the recessive condition will be unexpressed.
Mendel’s 2nd Las of Inheritance
Law of Segregation: during gamete formation there is a random separation (segregation) of dominant and recessive alleles.
Inheritance of a single character ( which in the case of purple and white flowers was purple flower).
Not the blending Hypothesis, ( light purple flowers).
3:1 ratio of the F2 generation
The F1 hybrids all have a Pp genotype.
When these plants cross, they end up with a 3:1 ratio where 75% of the plants in the F2 generation have the dominant phenotype and 25% have the recessive phenotype.
