Traits:The Puppeteering of

GeneticsBy: Stephen Romero

Aca-Deca 2013

A phenomenon in which one gene affects multiple unrelated phenotypic traits◦ Pleio- = Many; -tropic = affecting

Mendel’s experiment◦ Mendel observed that pea plants with white

flowers also have white stalks, and those that lacked white flowers equally lacked white stalks

Pleiotropy

A phenomenon in which multiple genes affect a single phenotypic trait◦ Poly- = many; -genic = of genes

Example include height, weight, and skin color, cancer risk, or any trait in which multiple factors come into play (generally quantitative values)◦ Colorblindness is an example in humans

in which the sex determines this. The X chromosome determines colorblindness, and since men only possess one X, they only need to inherit it from the mother. Women, however, need a color-blindness gene from both the mother and father to exhibit the trait.

Polygenic

William Bateson, with the help of Edith Saunders and Reginald Punnett, discovered that genes can be linked as a single unit during meiosis within the gametes, leading some traits not to follow the law of independent assortment◦ Thomas Morgan (Nobel Prize 1933) later proved the

theory of gene linkage in relation to the sex chromosome Meaning that some gene types could mutate with say

the Y-chromosome, leaving them to only be present in males

Linked Genes: Down w/ the System!

Sex is generally determined by genetics, but in many species, can also be dependent on:◦ Environment◦ Temperature◦ Chemicals◦ Social Structure

Also, in terms of sex chromosomes, the Y-chromosome is not always the deciding gene◦ In flies, the X-chromosome provides the necessary blueprints

for both sexes, but requires a second X to activate the female organs. The Y simply replaces the X

◦ In humans however, the Y chromosome determines the sex. The genitals are destined to be ovaries unless the SRY gene (located in the Y chromosome) says otherwise.

How is Sex Determined?

Pedigree analysis, the process of determining various genes within potential parents, helps genetic counselors allow potential parents to make decisions regarding child-birth based on the risks of disease and abnormalities

Karyotyping is genetic analysis performed on a developing fetuses◦ Amniocentesis is a the process of extracting fluid from

the fetal membrane via long needle in the uterine lining

◦ Chorionic villus sampling (CVS) actually extracts fetal membrane to be biopsied

Genetic Testing

1. Individuals within a species vary in their heritable traits; this is referred to as descent with modification

2. In every generation, more offspring are produced than can be supported by the environment

3. Individuals with the most favorable variations survive and go on to reproduce and are naturally selected

Darwin’s Theory of Evolution

(How I feel during AP Physics…)

~~Math Time~~