LU2 GENETICS

• The distribution of genes from generation to generation is a fundamental concept in genetics.
• The law of segregation and recombination are two important principles in genetics.
• Examples of six basic crosses are a fundamental part of genetics.
• Inheritance of genes at a single locus, also known as a monohybrid cross, is a fundamental concept in genetics.
• Gregor Johann Mendel, an Austrian monk, is considered the father of genetics and conducted landmark studies from 1856-1864, with thousands of crosses.
• Mendel chose pea plants as his experimental organism for hybridization, which is the mating or crossing between two individuals that have different characteristics.
• Hybrids are the offspring that result from such a mating and are presumed to be a blending of the parent traits.
• Mendel observed hybrids to be like one of the parents with respect to some traits, but not all.
• The morphological characteristics of an organism are termed characters or traits.
• A variety that produces the same trait over and over again is termed a true-breeder.
• In a Punnett square, write down the possible gametes each parent can make, for example, Male gametes: T or t and Female gametes: T or t.
• Mendel also performed dihybrid crosses, crossing individual plants that differ in two traits, for example, Trait 1 = Seed texture (round vs wrinkled) and Trait 2 = Seed color (yellow vs green).
• Mendel postulated that a pea plant contains two discrete hereditary factors, one from each parent.
• Alleles are different versions of the same gene.
• There are two possible patterns of inheritance for these traits.
• Fill in the Punnett square with the possible genotypes of the offspring.
• Mendelian factors are now called genes.
• The Law of Segregation & Recombination of Genes involves the segregation of genes in the gametes and the recombination of genes in the zygote.
• An individual with two different alleles, is termed heterozygous.
• An individual heterozygous for one pair of genes (Aa) is called monohybrid, referring to one pair of genes and the fact that those genes are heterozygous.
• An individual with two identical alleles is termed homozygous.
• The F2 generation contains seeds with novel combinations not found in the parentals.
• The two factors may be identical or different.
• The first three crosses in at least two ways: all individuals being mated are homozygous or only one kind of progeny is produced for each cross.
• Genotype refers to the specific allelic composition of an individual.
• The F2 generation showed an approximately 3:1 ratio of the two parental traits, which refuted a blending mechanism of heredity.
• Inheritance of genes at a single locus (Monohybrid Cross) involves the character of coat color in cattle and the trait of black & red.
• Progeny resulting from a cross among F 1 individuals
• Data suggested a particulate theory of inheritance.
• Heterozygotes produce two kind of gametes.
• Monohybrid cross:
• During gametogenesis (meiosis), the paired factors segregate randomly so that half of the gametes received one factor and half of the gametes received the other, as proposed by Mendel.
• Mating of two heterozygous individuals results in a genotypic ratio of 1:2:1.
• Involves two alleles : where one allele is completely dominant to the other, will produce:-
• A Punnett square is a grid that enables one to predict the outcome of simple genetic crosses, proposed by the English geneticist, Reginald Punnett.
• Genes recombine into pairs during the mating process.
• Mating of an individual to either of the parents or individuals similar in genotypes as one of the parents
• Phenotype refers to the outward appearance of an individual.
• When dealing with any trait in a population that is controlled by two alleles, A & a, three different genotypes are possible: AA, Aa, aa.
• Determine the relative proportions of genotypes and phenotypes of the offspring, for example, Genotypic ratio TT : Tt : tt 1 : 2 : 1 and Phenotypic ratio Tall : dwarf 3 : 1.