Transcript Mendel Discovers “Genes” 9-1

Heredity
Chapter 11
Transmission of characteristics from
parent to offspring is called
heredity
___________________.
The science that studies how those
characteristics are passed on from one
generation to the next is called
Genetics
___________________
The Father of Genetics is
_________________,
Gregor Mendel
a monk whose study of
genetic traits was the
beginning of our
understanding about how
genes work.
Mendel experimented
Pea plants
using ___________
MALE part of flower makes
_______
Pollen
________
FEMALE part of flower makes
__________
egg cells
_______
In pea plants, the pollen
normally joins with an
egg from the same plant
(self-pollinating) so
seeds have one parent
MENDEL’S PEA EXPERIMENTS
Mendel started his experiments with
peas that were _________________
true breeding
If allowed to
_________________
self pollinate
they would produce
____________________
offspring identical
to themselves.
MENDEL’S PEA EXPERIMENTS
Mendel removed pollen – making
parts and added pollen from another
plant.
cross-breed plants
This allowed him to _____________
different
with ______________
characteristics and study the results
A specific characteristic is called a
________
trait
MENDEL’S EXPERIMENTS
parental
P1 generation (_________)
generation
F1
F2 generation
When Mendel crossed PLANTS with 2
contrasting traits:
(EX: Tall crossed with short)
He always found same pattern:
1. ONLY one trait showed
in the F1 generation BUT . . .
2. Missing trait returned in
the F2 generation
in a 3:1 ratio
Must be a pair of factors
controlling a trait…one
can hide the other
The factors are GENES carried
on the pair of homologous
chromosomes
Different gene choices
for a trait are called
alleles
DOMINANT
__________________
= An allele
that ________
HIDES the presence of
another allele
RECESSIVE = An allele
__________________
that __________________
the
is hidden by
presence of another allele
DOMINANT/RECESSIVE
Dominant allele is represented by a
_____________
____________
capital letter.
(usually the first letter of the trait)
Recessive allele is represented by the SAME
____________
lower-case
_________________
letter.
T
EX: Tall = ______
t
Short =______
NOT S for short
HOMOZYGOUS
HETEROZYGOUS
When both alleles in the pair are
the _______,
SAME the organism is
_______________
HOMOZYGOUS or __________
PURE
EX: ____
or ___tt
TT
When both alleles in the pair are
_____________,
DIFFERENT the organism is
HETEROZYGOUS or _____________
HYBRID
_________________
Ex: ____
Tt
PHENOTYPE/GENOTYPE
genetic makeup of an organism
The ________________
is itsGENOTYPE
_____________
appearance an organism is
The ____________of
PHENOTYPE
its _____________
Why did the recessive trait disappear in the
F1 generation and reappear in the F2?
The pattern corresponds
movement
to the ____________
of
chromosomes during
______________
MEIOSIS
____________________
Image modified from:
http://www.laskerfoundation.org/rprimers/gnn/timeline/1866.html
REMEMBER
_____________
HOMOLOGOUS
chromosomes
SEPARATE
________________
during
ANAPHASE I
= _________________
SEGREGATION
Image modified from:
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
____
F1 offspring __________
received an allele for
tallness from their _______
TALL parent and an
allele for shortness from their ________
SHORT
parent.
The F1 plants ALL ___________
LOOK TALL
but are ___________
carrying an
allele for _____________
shortness
Images from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006
EXPLAINING the F1 CROSS
SEGREGATION
LAW OF ___________________
alleles are separated
when the F1 plants
______________
made gametes
When these gametes recombined to make the
recessive
F2 generation, the _____________
trait
_______________
reappears in ¼ of the offspring
Image from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006
MAKING A CROSS for only
ONE GENE trait =
a __________
MONOHYBRID
CROSS
____________________
DIHYBRID CROSSES
(2
traits)
http://mac122.icu.ac.jp/BIOBK/BioBookgenintro.html
MAKING A CROSS with
TWO gene traits
___________________=
DIHYBRID
CROSS
____________________
ASSORTMENT
LAW OF INDEPENDENT
__________________________
the factors are distributed to gametes
independently of other factors
Image modified from:
http://anthro.palomar.edu/mendel/mendel_1.htm