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Mendelian Inheritance Study (Key Terms (Mendelian Influence (Heterozygote,…
Mendelian Inheritance Study
Using Mendel’s theories, we can predict the characteristics of an offspring given the physical characteristics of the parents
Key Terms
Phenotype
expression of an inherited genotype
Alleles: Variants of a specific gene
Dominant
expressed as log as dominant allele is present; will be expressed even if paired w. different allele
Recessive
only expressed if no dominant allele is present; is expressed only when paired w. an identical allele
Genotype
Gentic makeup, is inherited alleles
Gene
segment of DNA that codes for a single protein or RNA (controls characteristics expressed)
Genetic Traits
biological characteristics passed on to offspring from parents
Punnett Square
chart used to determine the probability of different genotypes in the offspring of 2 parents
Mendelian Influence
Heterozygote
organism inherits two different alleles (Bb)
Monohybird Cross
A cross dealing w. only 1 characteristic
Homozygote
organism inherits 2 alleles of the same type (BB or bb)
Dihybrid Cross
A cross in which two independent traits are being determined by crossing parents that differ in genotype.
Non-Mendelian Influence: Inheritance does not always behave like Mendel’s pea plants.
Incomplete Dominance
dominant allele is not completely dominant, resulting in an intermediate phenotype
Polygenic Characteristics
A characteristic (a phenotype or genotype) that is controlled by more than one gene, with the possibility that each gene has two or more alleles. These genes may be located on the same or different chromosome.
EX: Skin color and height
will have the most phenotypes
Codominance
both alleles are expressed equally
Gametes
are sex cells and contain 1 copy of each gene
Hereditary
passing of characteristics from parents to offspring
Genotype & Phenotype
EX Genotype: The three possible genotypes are BB, bb, Bb (the order that the alleles are listed does not matter, so bB is the same as Bb)
Phenotype: homozygous dominant traits (BB) and heterozygous traits (Bb) will express the phenotype in one way. Homozygous recessive traits (bb) will express the phenotype in another way. A genotype containing at least one dominant allele will express the dominant allele.
Each parent contributes one allele, and the inherited alleles may be the same or different. The two alleles that an offspring inherits make up the genotype. The way an organism expresses the genotype is called the phenotype
New Traits
Although genes are inherited, their expression can be modified by interaction with the environment. New inheritable characteristics come from new combinations of genes or from gene mutations in reproductive cells, which will change the genetic makeup of the offspring.
Punnet Square
Ration 3:1 is typical for a monohybird cross where both parents are heterozygous
Predicting Multiple Traits
The ratio 9:3:3:1 is typical for a dihybrid cross between two heterozygous parents
Predicting the Phenotype
Purple: 75%; White: 25%
Predicting the Genotype
BB: 25%; bb: 25%, Bb: 50%
Mendels Experiments results
The two alleles that an offspring inherits make up the genotype
The way an organism expresses the genotype is called the phenotype.
Each parent contributes one allele, and the inherited alleles may be the same or different
1st Experiment: Law of Segregation
states that there are two factors controlling a given characteristic, one of which dominates the other, and these factors separate and go to different gametes when a parent reproduces
Theory of Hereditary
There are different versions of genes
For each characteristic, an organism inherits two alleles (heritable factors), one from each parent.
When gametes are formed, the two alleles (heritable factors) of each gene are separated
When two different alleles (heritable factors) are inherited together, one may be expressed, while the effect of the other may be “silenced.”
Law of Indep. Assortment
This law states that the factors controlling different characteristics are inherited independently of each other.
