BLAST FROM THE PAST: SBI3U

trait: a specific characteristic/feature represented by an organism

allele: a different form of the same trait

dominant: the form of a trait that always appear when an individual has an allele for it (BB or Bb)

recessive: the form of a trait that only appears when an individual has two (2) alleles for it (bb)

homozygous: an organism that has two (2) identical alleles of a gene (PP or pp)

heterozygous: an organism that has two (2) different alleles of a gene (Pp)

genotype: the combination of alleles for any given trait; the organism's entire genetic make-up   -----------------TRANSLATION----------------->

phenotype: the physical and physiological traits of an organism

Example: (respectively)

genotype: YY (homozygous dominant), Yy (heterozygous), yy (homozygous recessive)

phenotype: yellow seed, yellow seed [heterozygous: dominant is expressed], green seed

Parental (P) generation → First Filial (F₁) generation → Second Filial (F₂) generation

Punnett square: (a grid used to illustrate all possible genotypes of offsprings from genetic crosses)

test cross: a cross between a parent of unknown genotype and another of homozygous recessive genotype

Mendel's Law of Segregation: when gametes are formed, each must contain one allele from the two (2) of the parents

EXAMPLE: parent: Bb  possible gametes: B or b

Mendel's Law of Independent Assortment: if two (2) or more alleles are considered at the same time, the alleles have no influence over the separation of the others [disproven by linkage genes]

Law of Random Assortment: there is no telling in which gamete alleles will be in

incomplete dominance: first allele + second allele → new third allele (when heterozygous)

EXAMPLE: snapdragons (red + white → pink)

codominance: mix of first and second allele

EXAMPLE: roan horses/cows

multiple allelism: more than two (2) different alleles exist

EXAMPLE: blood types (A, B, O)

sex-linkage: alleles found only in the X chromosome has dominance over the Y chromosome

EXAMPLE: hemophilia

Cell → Nucleus → Chromosome → Chromatin → Gene → DNA→ Nucleotides ⤀ sugar, phosphate, nitrogenous bases

anti-parallel: 5-3 (other side) 3-5

Semi-conservative replication reduces the chance of genetic error because one strand of the original DNA is used as a template for the new, corresponding strand.