genetics and inheritance

trait

a characteristic that can vary from one individual to the nexr

pure breeding

off spring always have the same traits as parents

self-pollination

plant fertilizes itself

cross-pollination

one plant fertilizes another

P generation

parent generation

F1 generation

1st generation offspring

F2 generation

2nd generation offspring

Dominant

allele always expressed even if combined with recessive, written as uppercase

Recessive

allele expressed only if dominant is not present, written as lowercase

Mendels conclusion

• Inheritance of traits is controlled by genes

• These genes come in different forms called alleles; same gene different version of gene

• Some alleles are dominant while others are recessive

Genotype

genetic combination of alleles

Phenotype

physical characteristics or traits

Homozygous

both alleles are the same

Heterozygous

alleles are different

Hybrid

offspring of crosses of parents with different traits

Mendels law of independent assortment

• genes for two different traits are inherited independently

• there is no connection between them

Mendels law of segregation

• when gametes form, the alleles from each parent are segregated from each other

• each gamete carries a single allele for each gene

Gene linkage

genes that are located on the same chromosome will be linked together. travel together during gamete formation

Co-dominance

both alleles are dominant; expressed separately. Both are presented

Incomplete dominance

neither allele are dominant; heterozygote is a blend of phenotypes of the two homozygous. Combine and become one trait.

Blood type in humans

• 3 alleles possible (A,B,O)

• A and B are co dominant ; O is recessive

• Alleles notates as I^A, I^B, i

Polygenic inheritance

trait is controlled by interactions between 2 or more genes

occurs when one characteristic is controlled by two or more genes.

Lethal recessive alleles

• having two mutated copies of an essential gene may be deadly

• a carrier mens they both have the gene for the disease but they dont present with it

Polygenic traits

polygenic traits are traits that are made up by multiple different genes

Ex: AaBBcc

Examples of polygenic inheritance

height, eye color, hair color, skin color

Examples of x linked recessive orders

Hemophilia and color blindess