뒤로Chapter 9 Mendelian Genetics and Chromosomal Basis of Inheritance
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Heredity is the transmission of traits from one generation to the next.
Gregor Mendel is the father of genetics for deducing fundamental principles of heredity by breeding garden peas in the 1860s.
Peas have short generation times, large offspring numbers, distinct varieties, and controlled matings due to enclosed reproductive organs.
A character is a heritable feature (e.g., flower color), and a trait is a variant of that character (e.g., purple or white flowers).
A true-breeding variety consistently produces the same trait over many generations of self-pollination.
P generation: true-breeding parents; F1 generation: hybrid offspring of P; F2 generation: offspring from self-fertilization of F1.
F1 plants all had purple flowers; F2 showed a 3:1 ratio of purple to white flowers, indicating white was masked but not lost.
Alleles are alternative versions of a gene that account for variations in inherited characters.
Homozygous: two identical alleles (e.g., PP); heterozygous: two different alleles (e.g., Pp).
Allele pairs separate during gamete formation, so each gamete carries only one allele for each character.
Phenotypic ratio: 3 purple : 1 white; Genotypic ratio: 1 PP : 2 Pp : 1 pp.
Phenotype is the observable trait; genotype is the genetic makeup (allele combination).
Pairs of chromosomes carrying the same gene loci but possibly different alleles, one from each parent.
Separation of homologous chromosomes during anaphase I of meiosis leads to segregation of alleles.
Alleles of different genes assort independently during gamete formation, leading to genetic variation.
A 9:3:3:1 ratio of four phenotypes (e.g., round yellow, round green, wrinkled yellow, wrinkled green seeds).
Cross the individual with a homozygous recessive; offspring phenotypes reveal if the unknown is homozygous dominant or heterozygous.
Genes are located on chromosomes, which undergo segregation and independent assortment during meiosis, explaining inheritance patterns.
Some genes located close on the same chromosome tend to be inherited together, not following independent assortment.
Exchange of chromosome segments during meiosis producing recombinant gametes and new allele combinations.
It measures the percentage of recombinant offspring and helps map gene positions on chromosomes.
An ordered list of gene loci on a chromosome based on recombination frequencies.