8.1 Flashcards
What is a genotype?
The genetic constitution of an individual
Genotype refers to the specific alleles an organism carries.
Define homozygous.
Having two identical alleles for a specific gene
Example: AA or aa.
Define heterozygous.
Having two different alleles for a specific gene
Example: Aa.
What is a phenotype?
The observable physical or biochemical characteristics of an organism
Phenotype results from the interaction of the genotype with the environment.
What is a genotypic ratio?
The ratio of different genotypes in the offspring
Example: 1 AA : 2 Aa : 1 aa.
What is a phenotypic ratio?
The ratio of different phenotypes in the offspring
Example: 3 dominant : 1 recessive.
Contrast dominant and recessive traits.
Dominant traits mask recessive traits in heterozygous individuals
Dominant traits are expressed in the phenotype, while recessive traits are only expressed when homozygous.
What is co-dominance?
A genetic scenario where both alleles in a heterozygote are fully expressed
Example: AB blood type.
How did Mendel set up his genetic experiments?
By crossbreeding pea plants with different traits
He started with purebred plants and observed the inheritance patterns.
What were the generations Mendel studied?
P (parent), F1 (first filial), F2 (second filial)
Mendel consistently observed specific ratios in these generations.
What ratios did Mendel consistently see in the F1 generation?
All offspring showed the dominant trait
The F1 generation was uniform.
What ratios did Mendel consistently see in the F2 generation?
3:1 ratio of dominant to recessive traits
This ratio was typical for monohybrid crosses.
Contrast genotype and phenotype ratios in traits that are dominant/recessive vs. co-dominant.
Dominant/recessive: 3:1 phenotype, 1:2:1 genotype; Co-dominant: phenotype shows both traits expressed
Example: In a co-dominant trait, the phenotype might show spots or stripes.
Explain how a test cross works.
A test cross involves crossing an individual with an unknown genotype with a homozygous recessive individual
This determines whether the unknown genotype is homozygous or heterozygous.
Predict genotypic and phenotypic ratios for a trait with a dominant and recessive pattern.
Genotypic ratio: 1:2:1; Phenotypic ratio: 3:1
This applies to a typical monohybrid cross.
Predict genotypic and phenotypic ratios for a trait that is co-dominant.
Genotypic and phenotypic ratios are both 1:2:1
Example: In a cross of AB x AB, offspring can be AA, AB, or BB.
Predict genotypic and phenotypic ratios for a trait that has multiple alleles.
Depends on the specific alleles involved; typically, multiple phenotypes can arise
Example: ABO blood type system has three alleles (I^A, I^B, i).
Predict the parent genotypes based on the phenotypic ratio of offspring.
Use the observed phenotypic ratio to backtrack potential parent genotypes
Example: A 9:3:3:1 ratio suggests a dihybrid cross between heterozygotes.
