Genetics A Monk and his Methods

Gregor Mendel In 1865 he published his observations of pea plants. His work went unnoticed for several decades, before the realization of his genius set in.

What did he do? He worked with Pea plants. He noted several variations in the characteristics of his plants Variations such as Flower color (Purple or White) Seed Texture (Round or Wrinkled)

Careful Observations Mendel did several experiments where he cross-bred (mated) plants of various characteristics. He took careful notes and recorded all of his observations Mendel made some astounding conclusions

The Conclusions Mendel noted that some traits seemed to prevail over others….. An example: Mendel cross bred a pea plant with white flowers and a pea plant with purple flowers. The majority of plants produced had purple flowers, few had white flowers.

Why is this important? These observations lead to the conclusion that certain traits are DOMINANT over other traits. The traits that are not DOMINANT are called RECESSIVE.

Patterns of Inheritance Mendel noted these patterns of inheritance among pea plants. Today we can apply these ideas to human inheritance. This family inherited the “Cat-face gene”.

Let’s Take a Closer Look What is actually happening when traits are inherited???? Remember traits (genes) are carried on CHROMOSOMES. You have TWO copies of EACH chromosome. This means you have TWO copies of EACH gene.

Your Genes You received one half of your genes from your mother and the other half from your father. These genes complement each other and express themselves as a PHENOTYPE. PHENOTYPE- physical characteristic of an organism (What you see)

Phenotype Vs. Genotype Your phenotype (what you see) may be different than your GENOTYPE GENOTYPE- the combination of ALLELEs that an organism has for a trait ALLELE- a variation of a trait

Let’s Check it Out

Dominant Vs Recessive Some alleles are Dominant and some are Recessive

Homozygous and Heterozygous Genotypes can be Heterozygous or Homozygous. A Heterozygous genotype has one of each allele. (Aa) A Homozygous genotype only has one type of allele (aa or AA)

Recessive Only those individuals who have the homozygous recessive genotype will have the recessive phenotype.

References http://www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f1.gif http://www.laskerfoundation.org/rprimers/gnn/timeline/images/first_second_generation.gif http://www3.sympatico.ca/the_adams_family/cat-family.png http://www.awa.com/norton/figures/fig1307.gif http://library.thinkquest.org/C0118084/Gene/Genetic_variation/dominant_recessive_files/homologous_chromosomes.gif http://site.voila.fr/bioafb/loismend/genelapi.GIF http://www.glasgowzoo.co.uk/images/warmblooded/wal2.jpg