Mendelian Genetics
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Transcript Mendelian Genetics
Mendelian Genetics
Genetics: The Scientific Study of
Heredity
Mendel –Austrian Monk
Born 1822
Spent years studying science and mathematics
Worked at a Monastery and taught High School.
Also in charge of the monastery garden- This
work is where Mendel developed his theories on
Genetics
Sexual Reproduction
Mendel understood that pollen contained the
male reproductive cells and that the female
portion of the flower produces the egg.
When the male and female sex cells are joined
together this is called fertilization and a seed is
formed.
http://anthro.palomar.edu/mendel/mendel_1.htm
Pea Plants:
Pea plants can self-pollinate-meaning the
pollen of a plant can fertilize the same
flower (Inbreeding). This produces a seed
with the same characteristics as the parent
plant (true-breeding/homozygous).
These plants would produce only green seeds
only yellow seeds, only tall seeds,etc
Cross-Pollination
Mendel wanted to produce
seeds by joining male and
female reproductive cells from
different plants-so he dusted
pollen from one plant on to
another to cross-pollinate.
This can also be done
naturally by pollinators such
as bees.
http://www.fs.fed.us/wildflowers/pollinators/images/xpollination_ani.gif
Data/Observation
Pollen Pictures Day 2
Lilium oriental
(+) control
After 120min
~100 µm
Pollen tube
Picture by Charles Beckius
Genes vs. Alleles
Genotype – the actual codes for a trait
ex. BB,Bb,bb
Phenotype- the traits seen
Dominant vs. Recessive
Principle of dominance states that some
alleles are dominant and others are
recessive.
Capitol Letters =dominant traits=if gene is
present, trait will always be seen.
Lower case letter =recessive traits=hidden traits.
BB x bb = Bb
True-breeding/homozygous
BB or bb pure characteristics from having
all the same alleles
Hybrids/heterozygous
The offspring of crosses between parents
with different traits are called hybrids.
BB x bb = Bb
brown
x
blue
Hybrid brown
Traits
Mendel studied 7 different pea plant traits.
Seed shape- round vs. wrinkled
Seed color – yellow vs. green
Seed coat color- gray vs. white
Pod shape- constricted vs smooth
Pod color green vs. yellow
Flower position – axial vs. terminal
Plant height- short vs. tall
haploid
haploid
+
haploid
Diploid
http://www.mansfieldct.org/schools/mms/staff/hand/genpunnet1.htm
Monohybrid cross
Mendel’s
P, F1, and F2 Generations
P-parent generation
t
T
T
Tt
Tt
Tt
Tt
TT x tt
Offspring of the P generation is
the F1 generation
Cross the F1-1st filial generation
T
T
t
Tt x Tt
t
TT
Tt
Tt
tt
To get the F2 “filial generation
MENDEL's first law is the principle of
uniformity. It says that, if two plants that
differ in just one trait are crossed, then the
resulting hybrids will be uniform in the
chosen trait.
http://dwb.unl.edu/Teacher/NSF/C08/C08Links/www.rrz.uni-hamburg.de/biologie/b_online/e08/08a.htm
MENDEL's second law is the principle of
segregation. It states that the individuals
of the F2 generation are not uniform, but
that the traits are segregated
MENDEL's third law is also called the principle of
independent assortment. It says that every trait
is inherited independently of the others and it thus
covers the case that new combinations of genes
can arise, which were not existing before. We
know today that this principle is just valid in the
case of genes that are not coupled, i.e. that are
not located at the same chromosome.
MENDEL's 4th law is also called the principle of
attraction. It says that since every sperm and egg are
polar and that since sperm are slightly positive and ova
is slightly negative they are always attracted to each
other. In addition some alleles are also polar which
increase the combination of certain characteristics
combining together. For example blonde hair and blue
eyes are more likely to developed together since those
alleles are polar opposites. However this only occurs if
the alleles are not located at the same chromosome.
Incomplete Dominance
http://dwb.unl.edu/Teacher/NSF/C08/C08Links/www.rrz.uni-hamburg.de/biologie/b_online/ge08/01.gif
In-complete
dominance
Co-Dominance
http://media.nasaexplores.com/lessons/02-064/images/image2.jpg
Dihybrid Cross
http://bio.winona.edu/berg/ILLUST/mend7.gif
A
i
o
i
http://www.biologycorner.com/resources/bloodtype_chart.gif
o
i
B
i
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/images/lab7.h28.jpg
Sex-Linked Traits
http://www.biologycorner.com/bio2/specialgenetics.html
http://www.uni.edu/walsh/xlink2.gif
Pedigree
http://www.koshland-science-museum.org/img/sub/teachers/webquest-gd-007.jpg