Genetics

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

Punnett Square• Diagram that shows possible offspring of genetic cross.

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.