Traits and Inheritance

Mendel’s Pea Experiment

Human Chromosomes

Meiosis Square Dance!

Mitosis vs. Meiosis

EXCEPTIONS TO MENDEL’S PRINCIPLES

Incomplete dominance- There isn’t always clear dominance of one allele over the other.

Haploid vs. Diploid vs. Polypoid-Not all organisms inherit two alleles

 

Gene Linkage and Crossing-Over- Sometimes genes do NOT sort independently like in the activity we did with “Dragon Genetics.”  In fact, sometimes genes are linked together because the genes are on the same chromosome.

For example, the “A” and “B” alleles will both be passed on together if the lower chromosome is inherited.  “A” and “B” are linked because they are on the same chromosome.  Similarly, “a” and “b” are linked in the other chromosome.

 Sometimes, during the process of Meiosis, genes will be swapped between chromosomes.  This is called crossing-over or recombination.

One gene is NOT always in charge of ONE trait

Sometimes, one gene influences more than one trait.  This is called Pleitropy.  For example, the gene for pigmentation in cats (eye color/fur color) influences a cat’s ability to hear.  Apparently, approximately 40% of cats with white fur and blue eyes are deaf. Cats with one blue eye are sometimes they are deaf in one ear.

Sometimes, many genes are in charge of a single trait.  These traits are called Polygenic traits.  Eye color and hair color are the result of several genes acting together.

 

 

 

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