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Understanding Inheritance (Modeling Inheritance (Punnett Square (Model…
Understanding Inheritance
What controls traits?
Chromosomes
Chromosomes contain genetic information that controls traits.
Genes and Alleles
Gene - Section of the chromosome that has genetic information for one trait
Alleles - different forms of genes
Genotype and Phenotype
Symbols for Geneotypes
Uppercase letters represent dominant alleles and lowercase letters represent recessive alleles.
Homozygous and Heterozygous
Homozygous - When the two alleles of a gene are the same.
Heterozygous - When the two alleles of a gene are different.
Phenotype - How a trait appears of is expressed.
Genotype - The two alleles that control phenotype of a trait.
One factor from each Parent controls each trait.
Modeling Inheritance
Punnett Square
Model used to predict possible genotypes and phenotypes of offspring.
Analyzing a Punnett Squares
If there are any capital letters in a box of a punnett square the genes for that box going to be dominant. If there are two lower case letters in a box of a punnett square the genes for that box is going to be recessive.
Using Ratios to Predict
Ratios simplify information on a punnett square make it easier to see the chances of a dominant or recessive trait being passed down to offspring.
Pedigrees
A pedigree shows phenotype of genetically related family members and can help determine genotype.
Models are used to predict traits of offspring.
Complex Patterns of Inheritance
Types of Dominance
Incomplete Dominance
Incomplete dominance - when the offspring's phenotype is a combination of the parents' phenotypes
Codominance
Condominance - When both alleles can be observed in a phenotype
The presence of one dominant allele produces a dominant phenotype but not all allele pairs have a dominant-recessive interaction.
Multiple Alleles
Some genes have more than two alleles like human blood.
Polygenic Inheritance
Polygenic inheritance occurs when multiple genes determine the phenotype of a trait.
Genes and the Environment
Scientists have learned that genes are not the only factors that affects phenotype but the environment plays a roll too.
