Transcript 01 Chapter 11-1 notes

CHAPTER 11: GENETICS
18 THINGS YOU SHOULD KNOW ABOUT
GENETICS
Every organism has an inherited
set of characteristics from their
parent or parents. These are our
genes.
Genetics is the study of heredity.
GENETICS

Passing of genes from parent to offspring
 Asexual
reproduction: One parent
 Low
diversity
 Essentially mitosis
 Sexual
 High
reproduction: Two parents
diversity
 Mixes up DNA through meiosis
GREGOR MENDEL
Father of genetics
 Austrian monk born in
1822

A
priest who studied
science an mathematics
 Worked at a monastery
and taught high school
GREGOR MENDEL

Carried out a series of
experiments in the
monastery’s garden
 Observed
fertilization
process of garden
peas
MENDEL’S FIRST EXPERIMENT

Crossbred truebreeding plants
 Truebred
– an organism who produce identical
offspring to themselves

Observed 7 traits in offspring
 Trait:
A specific characteristic that varies based on
what genes are inherited.
SEXUAL REPRODUCTION IN PLANTS
Pea flowers are normally self-pollinating, which means that sperm cells in
pollen fertilize the egg cells in the same flower. The seeds then grow plants
with the same characteristics as the single parent.
Mendel wanted to produce seeds via cross-pollination (joining male and female
reproductive cells from two different plants.)
Mendel accomplished crosspollination by cutting away the
pollen-bearing male parts &
then dusting pollen from
another plant onto the flower.
This process produced seeds
that had two different plants
as parents. This made it
possible for Mendel to crossbreed plants with different
characteristics, and study the
results.
MENDELS’S FIRST EXPERIMENT

P: Parent generation
 Cross

2 truebreds
F1: Filial 1 generation
 Produced
hybrids:
Resulting offspring from
two truebred parents
with different traits
 Next, cross-fertilized
hybrids from F1
generation

F2: Filial 2 generation
MENDEL’S CONCLUSIONS
1)
2)
Biological inheritance
is determined by
“factors” that are
passed from one
generation to the next.
Principle of
dominance: states that
some alleles are
dominant and others
are recessive.
WHAT WE CALL “FACTORS” TODAY
•
Genes are the chemical
factors that determine
traits.
•
The different forms of a
gene are called alleles.
•
Genes are located in
specific positions on
chromosomes.
MENDEL’S CONCLUSIONS
Mendel had one more question remaining about his crosses… What happened to the
alleles that disappeared? Ex: Cross a Tall and a Short plant and all of the F1 offspring
were tall.
When Mendel allowed the F1 generation to self pollinate, he was shocked to see the
missing alleles reappear.
Principles of Dominance
Section 11-1
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Principles of Dominance
Section 11-1
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Principles of Dominance
Section 11-1
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
LAW OF SEGREGATION
Mendel correctly assumed that the allele for shortness was masked by the dominant
tall allele, but was still puzzled on why it showed up again in the F2.
He knew that the short allele must
have separated or SEGREGATED
from the tall allele at some point.
Mendel again correctly
hypothesized that this segregation
may have happened during sex cell
or gamete formation.
During gamete formation, alleles
segregate so that each gamete
carries a single copy of each
gene.