Mendel's principles of heredity

1.1 & 1.2

Artificial selection

Selective breeding of domesticated plants & animals with desirable characteristics

Natural selection

Individuals with certain traits are more likely to survive & reproduce in a given environment

Domestication syndrome in animals

Floppy ears, variations in coat colour, shorter muzzle smaller teeth, prolonged juvenile behaviour, extended breeding cycle & hormonal changes

Genes

For each trait, carry 2 copies of a unit of inheritance, one from each parent

Alleles

Alternative units of inheritance of a single gene

Monohybrids

Individuals having two different alleles of a single gene

Gametes

Specialized cells that carry genes between generations (eggs & sperm) only a single copy of each gene

Heredity

The way genes transmit traits from parents to offspring

Genome / genotype

Description of genetic makeup of an individual; alleles an individual possesses

Genetics

Pursues an explanation

Phenotype

Observable traits determined by genotype that an individual exhibits

Blended inheritance

Idea that parental traits become mixed & forever changed in the offspring

What did Mendel do differently

Choose peas which offered many advantages, he examined inheritance of clear-cut alternatives for particular traits, collected I perpetuated lines of peas that bred true, made reciprocal crosses, worked with large numbers of plants accounting for all offspring & asked questions about his observations

Self-fertilization (selfing)

Both egg & pollen come from the same plant, often same flower

Cross-fertilize (cross)

Remove stamens from flowers of one plant to prevent selfing then brushed pollen from the other plant onto the pistils of the firstplant

Discrete traits

Clear-cut alternatives for particular traits. Either-or traits. No intermediate forms exist. Purple vs white

Continuous traits

Show many intermediate forms such as height, skin colour

Pure breeding ( true-breedings lines )

Produce offspring carrying specific parental characteristics that remain constant from gen to gen

Inbred

Mated only to each other for many generations

Hybrids

Mating of parents with antagonistic characteristics

Antagonistic pairs

Constant but mutually exclusive alternatives ex: purple vs white flowers or yellow vs green seeds

Reciprocal crosses

Reverse the characteristics of male & female parents thus controlling if aparticularcharacteristic was transmitted via egg or sperm

Mono hybrid crosses

Experiments involving hybrids for a single trait

P parental generation

Planted pure-breeding green peas & pure-breeding yellow peas grown into

First filial (f1) generation

Produced by crosses of pure-breeding parental plants, all of which resembling one parent

Second filial generation ( F2)

Self pollination F1 plants resulted in F2 generation with a 3:1 ratio of individuals resembling the two original parental types

Law of segregation

The two alleles of each gene separate (segregate) during gamete formation, & then unite at random one from each parent at fertilization restoring the zygote

Zygote

Fertilized egg carrying two copies of the gene for every trait

Punnet square illustrates

Product & the sum rule which predict the likelihood that a particular combination of events will occur

Product rule

Probability of 2 or more independent events occurring together is the product of the probabilities that each event will occur by itself

Sum rule

Probability of either of two mutually exclusive events occurring is the sum of their individual probabilities

Homozygous

The 2 copies of the gene that deter mine the particular trait in question are the same

Heterozygous

Genotype with different alleles for a trait, hybrid

Testcross

Use to uncover unknown genotype, when inheritance pattern & phenotype is known, use homozygous recessive individual for genotype in question

Dihybrid

Individuals that carry different alleles of 2 genes

Parental types

Looked either like the original yellow round parent or like the green wrinkled

Recombinant types

New combinations of characteristics occur that never not seen in parental lines ex: yellow & wrinkled or green ground

Independent assortment

During gamete formation, different pairs of alleles segregate independently of each other

Multihybrid crosses

Mating between the individuals that differ in 3 or more traits

Principles emerging from molecular discoveries

Specific gene determines a specific protein, activity of protein may affect the phenotype. The dominant allele determines a normally functioning protein, while the recessive allele does not specify a functional protein

Polymorphic

Gene has multiple alleles that normally occur in population

Monomorphic

Genes have only one allele that is normally present in a population (others are rare)

Tetraploid

4 copies of every chromosome

Law of independent assortment

During gamete formation different pairs of alleles segregate independently of each other producing the 9:3:3:1 phenotypic ratio

Probability laws