Terms to Know:
Blending hypothesis
Proposed in early 1800’s
Red-flowered plant crossed with yellow-flowered plant
Red and yellow hereditary material blend and produce orange-flowered offspring
Obvious faults
Particulate hypothesis parents pass on separate and distinct factors (genes) to their offspring that determine traits stressed that factors (genes) retain their own identities generation after generation (even if they are not expressed in each generation) like different colored marbles, not paint (could be mixed together and still separated)
Traits
distinguishing characteristics that are inherited such as eye color, leaf shape, tail length, etc.
Genetics
study of inheritance and patterns of variation in organisms
Purebred
true-breeding
Cross
mating of two organisms
Heredity
the passing of traits to offspring from its parents or ancestors
Cross fertilization (aka cross pollination)
1 transfer of pollen grains from anther of one flower to stigma of another flower
Self-fertilization (aka self-pollination) transfer of pollen grains from anther to stigma of same flower
Law of segregation demonstrated traits are inherited as discrete units (refutes blended hypothesis) organisms inherit 2 copies of each gene, one from each parent organisms donate one copy of each gene in gametes (meaning 2 copies of each gene segregate, or separate, in meiosis)
Locus
specific position on a pair of homologous chromosomes
Gene
a piece of DNA that provides a set of instructions for making a certain protein
Allele
any alternative forms of a gene that may occur at a specific locus
1 usually represented as a single letter
2 usually letters will be given to you in a problem
Homozygous
2 of same alleles at a specific locus (PP or pp)
Heterozygous
2 different alleles at a specific locus (Pp)
Genome
All of an organism’s genetic material; aka all of an organism’s genes
Genotype
Refers to genetic makeup of a specific set of genes
Phenotype
physical characteristics, or traits, for an individual organism
Dominant
allele that is expressed when two different alleles or dominant alleles are present (uppercase letter represents)
Recessive
Allele that is expressed only when two copies are present (lowercase letter represents)
Punnett Square
Grid system for predicting all possible genotypes resulting from a cross
Monohybrid cross crosses that examine inheritance of only one specific trait
Testcross
Cross between an organism with an unknown genotype and an organism with the recessive phenotype (homozygous recessive)
Resulting offspring show whether unknown parent is homozygous dominant or heterozygous
Dihybrid cross crosses that examine inheritance of two different traits
Mendel performed these crosses with purebred (true-breeding) plants
1 F1: all heterozygous and looked same
2 F2: 9:3:3:1 phenotypic ratio
Law of independent assortment
Mendel found regardless of combination of traits, the presence of one trait did not affect presence of another law of independence assortment = allele pairs separate independently of each other during gamete formation (meiosis)
Probability
The measure of the likeliness that an event will occur
Crossing over exchange of genetic material between homologous chromosomes exchange occurs during prophase 1 of meiosis
Crossing over can produce a single chromosome that contains a new combination of genetic information from different parents, a result called genetic recombination
Genetic linkage
The tendency that gens who are close together on a chromosome, to be linked together during meiosis
Carrier
Someone who carries the trait to pass on to offspring but doesn’t have the trait themselves
Sex-linked genes