Transcript Gregor Mendel TRAIT

11-1: The Work of Gregor Mendel
Biology 2
Introduction
• Every living thing has a set of
characteristics inherited from
its parent(s)
• Scientists have discovered that
heredity helps understand
what makes species unique
• GENETICS: scientific study of
heredity
Gregor
Mendel
• Gregor Mendel was born in 1822
in Czech Republic
• Became a priest and teacher at
monastery
• Studied math and science at
University of Vienna
• Was in charge of monastery
garden
Gregor
Mendel
• Mendel was interested in
monastery garden peas
• He knew that parts of flowers
contain male/female sex cells
– Stamen produce pollen (Sperm)
– Pistil produce ovules (Egg)
Gregor
Mendel
• FERTILIZATION: process in
sexual reproduction in which
male and female reproductive
cells join to form a new cell
• Pea plant flowers are normally
self-pollinating
– Pollen fertilizes ovule of same
flower
Gregor
Mendel
• Seeds that are produced by
self-pollination inherit all their
characteristics from the one
parent (true-breeding!)
• All the plants that Mendel took
care of were true-breeding
Gregor
Mendel
• TRUE-BREEDING: term used to
describe organisms that
produce offspring identical to
themselves if allowed to selfpollinate
• In true-breeding, one set
would produce only tall
plants; one set would produce
only purple flowers; etc…
Gregor
Mendel
• Mendel wanted to produce seeds
from different plants
• He had to prevent self-pollination
– He did this by removing the stamen
from flowers
• Used the removed stamen to
fertilize other flowers, called
cross-pollination
– Allowed Mendel to study different
characteristics
Genes and
Dominance
• TRAIT: specific characteristic
that varies from one individual
to another
• Mendel studies 7 different pea
plant traits
– Each of the 7 traits had 2
different “looks” – now called
alleles
• ALLELES: one of a number of
different forms of a gene
Genes and
Dominance
• Original plants used for
fertilization are called P
(parental) generation
• Offspring are called F1 (first
filial)
– Filial = Latin word for
son/daughter
Genes and
Dominance
• HYBRID: offspring of crosses
between parents with different
traits
• After creating hybrid F1 offspring,
Mendel studied what the plants
looked like
• Mendel noticed that offspring
had characteristics of only 1
parent
– Other parent characteristics
“disappeared”
Genes and • Mendel learned 2 things from his
experiments:
Dominance
1. Biological inheritance is
determined by factors that are
passed from one generation to
the next
– These factors are now called genes
Pg 148
• GENES: sequence of DNA that
codes for a protein and thus
determines a trait
Genes and
Dominance
2. Principle of dominance states
that some alleles are
dominant and others are
recessive.
• dominant allele will always
show dominant trait
• Recessive allele will only show
if there is no dominant allele
Segregation • Mendel wanted to know if the
recessive trait disappeared
• Allowed all 7 hybrid F1 offspring
to produce an F2 generation
– In F2 generation, recessive
showed up again!
• Figured out that the stronger
(dominant) allele “covered up”
the weaker (recessive) allele
Segregation • SEGREGATION: separation of
alleles during gamete
formation
• When sex cells (gametes) are
created, dominant and
recessive alleles have to
“separate” from each other
– GAMETES: specialized cell involved
in sexual reproduction
Section Assessment
1. ____________: process in sexual
reproduction in which male and female
reproductive cells join to form a new
cell
2. What does true-breeding mean?
3. What 2 things did Mendel learn from his
experiments?
Mendel – From the Garden to the
Genome
http://www.youtube.com/watch?v=6OPJnO9W_rQ