Genetics• Genetics – branch of
biology that deals with patterns of inheritance, or heredity.
• Heredity- biological process by which parents pass on genetic information to their offspring through their gametes
• An Austrian monk, Gregor Mendel, is said to be the “father of genetics” because he performed series of experiments on pea plants in the mid 1800’s.
Principles of Mendelian Genetics
• No knowledge of genes and chromosomes • Careful observations of the inheritance
pattern of specific traits found in pea plants (mathematical analysis of large numbers of offspring)
• Concluded- traits controlled by pairs of inherited ‘factors’ with one member of each pair coming from each parent organism.
Major concepts• P (parent generation)
Organisms that are used to begin studies • F1 (first filial generation)
Offspring produced by crossing members of parent generation
• F2 (second filial generation)Offspring crossed between members of the F1 generation
Major conceptsMendel’s Principle of
Dominance• Ex: cross peas that were
pure for contrasting traits; pure tall with pure short. All offspring showed only one of the two contrasting traits. All were tall.
• Dominant- allele that is expressed – (capital letter)• Recessive- allele not expressed(lower case of same letter)
http://www.teachersdomain.org/resources/hew06/sci/life/gen/dominantgene/index.html
• Homozygous -two genes of a pair of alleles are the same (aka pure) TT or tt
• Homozygous dominant TT• Homozygous recessive tt
• Heterozygous- two genes of a pair of alleles are different (aka hybrid) Tt
• Genotype- The genetic makeup of organism- TT, Tt, tt
• Phenotype- Physical appearance of an organism that results from its genetic makeup. TT & Tt tall, tt short
Mendel’s Law of Segregation (video)
http://www.teachersdomain.org/resources/hew06/sci/life/gen/mendelinherit/index.html
Segregation and Recombination• When gametes are formed
during meiosis, the two chromosomes of each homologous pair separate, or segregate randomly.
• Each gamete contains only one allele for each trait.
• After gametes fuse during fertilization, the resulting zygote cell contains pairs of homologous chromosomes, but new combination for alleles may be present.
• Ex: Principle of Segregation.