monohybrids & dihybrids 2/3

theory of pangenesis

proposed by hippocrates

“seeds” produced by all parts of the body are collected in the reproductive organs then passed to the offspring at the moment of conception

theory of preformation

homunculus → little man that early microscopists though they saw in the sperm, which simply develops in the womb

blending theory of inheritance

factors that control hereditary traits are malleable and can blend together from generation to generation

gregor mendel

the father of genetics

played with pea plants

trait

the specific property of a characteer

ex: eye color is characteristics w blue and brown being the ____

characteristic/character

morphological trait of an organism

gene

an inherited factor (region of DNA) that determines a characteristic

allele

one of two or more different forms of a gene

locus

physical location on a chromosome occupied by a gene

genotype

the set of alleles possessed by an individual organism

phenotype

the physical appearance or manifestation of a trait associated with a particular genotype

heterozygote

two different alleles at a locus

homozygote

two of the same alleles at a locus

pure/true breeder

strain that produces the same trait over several generations

homozygous for the given trait

stamen

male reproductive part, producing pollen

pistil

female reproductive part, containing the ovules and developing into the fruit

hybridization

the mating or crossing of two individuals with different traits for a character

hybrid

the offspring of a cross of different traits

cross-fertilization

pollen and egg are from different plants

self-fertilization

pollen and egg are from the same plant → occurs without manipulation in peas

monohybrid cross

cross two variants of a single characteristic (pure breeders)

ex: plant height, seed shape, flower color

P generation

the parental cross

use true breeding individuals (homozygous)

F1 generation

the result of the P generation cross

F2 generation

the result of crossing individuals in the F1 generation

the principle of segregation (mendel’s first law)

each individual possess two alleles for each character

each allele separates during the formation of gametes

each allele is separated in equal proportions

concept of dominance

when two alleles for a single character are found in the same individual

dominant

its phenotype is expressed

recessive

its phenotype is not expressed

punnett square

a grid that can be used to predict the outcome of a simple genetic cross

back cross

a cross between an F1 genotype and either of the parental genotypes

test cross

an individual of unknown genotype (A_) is crossed with an individual homozygous recessive (aa) for the given trait to reveal the unknown genotype

loss of function (LOF) allele

if a mutation occurs in that allele, the function for which it encodes is also lost

variant of a gene that results in a reduced or abolished function of the protein or gene product it encodes, often due to mutations that disrupt the protein's structure or function

dihybrid cross

a cross between individuals that differ in two characters

the law of independent assortment (mendel’s second law)

alleles at different loci separate independently of one another

two different genes will randomly assort their alleles during the formation of haploid gametes

multiplication (product) rule

the probability of two or more independent events occurring together is calculated by multiplying their independent probabilities

clue = AND

addition rule

probability of any one of two or more mutually exclusive events is calculated by asking the probabilities of these events

clue = EITHER/OR

branching diagram

used to determine the proportions of each phenotype