Download Traits: The Puppeteering of Genetics

By: 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

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 colorblindness gene from both the mother
and father to exhibit the trait.

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

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 Ychromosome 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.


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
1.
2.
3.
Individuals within a
species vary in their
heritable traits; this is
referred to as descent
with modification
In every generation,
more offspring are
produced than can be
supported by the
environment
Individuals with the most
favorable variations
survive and go on to
reproduce and are
naturally selected
(How I feel during AP Physics…)