Gregor Mendel conducted experiments with pea plants to study inheritance of traits. He found that traits are passed from parents to offspring through discrete units called alleles, and that alleles segregate and assort independently during reproduction according to his principles of segregation and independent assortment. Mendel's discoveries established the foundations of classical genetics.

1. Submitted by:
Deborah G. Daquioag

2. Mendelian Genetics Definitions
• Allele - one alternative form of a • Heterozygote - an individual
given allelic pair; tall and dwarf which contains one of each
are the alleles for the height of a member of the gene pair; for
pea plant; more than two alleles example the Dd heterozygote
can exist for any specific gene, • Phenotype - literally means "the
but only two of them will be form that is shown"; it is the
found within any individual outward, physical appearance of
• Homozygote - an individual which a particular trait
contains only one allele at the • Genotype - the specific allelic
allelic pair; for example DD is combination for a certain gene or
homozygous dominant and dd is set of genes
homozygous recessive; pure lines • Monohybrid cross - a cross
are homozygous for the gene of between parents that differ at a
interest single gene pair (usually AA x aa)
• Allelic pair - the combination of
two alleles which comprise the
gene pair

3. Mendelian Genetics Definitions
• Dominant - the allele that • Dihybrid cross - a cross
expresses itself at the expense between two parents that
of an alternate allele; the differ by two pairs of alleles
phenotype that is expressed in (AABB x aabb)
the F1 generation from the • Dihybrid- an individual
cross of two pure lines heterozygous for two pairs of
• Recessive - an allele whose alleles (AaBb)
expression is suppressed in
the presence of a dominant
allele; the phenotype that
disappears in the
F1 generation from the cross of
two pure lines and reappears
in the F2 generation

4. Mendelian Genetics Definitions
• Backcross - the cross of an • Monohybrid - the offspring of
F1 hybrid to one of the two parents that are
homozygous parents; for pea homozygous for alternate
plant height the cross would alleles of a gene pair
be Dd x DD or Dd x dd; most • Dominance - the ability of one
often, though a backcross is a allele to express its phenotype
cross to a fully recessive at the expense of an alternate
parent allele; the major form of
• Testcross - the cross of any interaction between alleles;
individual to a homozygous generally the dominant allele
recessive parent; used to will make a gene product that
determine if the individual is the recessive can not;
homozygous dominant or therefore the dominant allele
heterozygous will express itself whenever it
is present

5. Mendel’s Genetics
• By the 1890's, the invention of
better microscopes allowed
biologists to discover the basic
facts of cell division and sexual
reproduction.
• The focus of genetics research
then shifted to understanding
what really happens in the
transmission of hereditary traits
from parents to children.
• A number of hypotheses were
suggested to explain heredity, but
Gregor Mendel , a little known
Central European monk, was the
only one who got it more or less
right.

6. Mendel’s Genetics
• His ideas had been published
in 1866 but largely went
unrecognized until 1900,
which was long after his
death.
• His early adult life was spent in
relative obscurity doing basic
genetics research and teaching
high school mathematics,
physics, and Greek in Brno
(now in the Czech Republic).
• In his later years, he became
the abbot of his monastery
and put aside his scientific
work.

7. Mendel’s Genetics
• Mendel picked common
garden pea plants (Pisum
sativum) for the focus of
his research because they
can be grown easily in
large numbers and their
reproduction can be
manipulated
• Mendel discovered that
certain traits show up in
offspring without any
blending of parent
characteristics.

8. Mendel’s Genetics
• The seven traits that are easily
recognized and only occur in
one of two forms:
1) flower color is purple or
white
2) flower position is axil or
terminal
3) stem length is long or short
4) seed shape is round or
wrinkled
5) seed color is yellow or green
6) pod shape is inflated or
constricted
7) pod color is yellow or green

9. Mendel’s Genetics
• Pea plants have both male and
female reproductive
organs. As a result, they can
either self-pollinate
themselves or cross-pollinate
with another plant.
• In his experiments, Mendel
was able to selectively cross-
pollinate purebred plants with
particular traits and observe
the outcome over many
generations.
• This was the basis for his
conclusions about the nature
of genetic inheritance.

10. Mendel’s Genetics
• In cross-pollinating plants that either produce yellow or
green pea seeds, Mendel found that the first offspring
generation (f1) always has yellow seeds.
• However, the following generation (f2) consistently has
a 3:1 ratio of yellow to green.
(all heterozygous)

11. Mendel’s Genetics
• This 3:1 ratio occurs in later generations as
well. Mendel realized that this was the key to
understanding the basic mechanisms of
inheritance.

12. Mendel’s Genetics
• He came to three important
conclusions from these
experimental results:
1) that the inheritance of each
trait is determined by
"units" or "factors" that are
passed on to descendents
unchanged
2) that an individual inherits
one such unit from each
parent for each trait
3) that a trait may not show up
in an individual but can still
be passed on to the next
generation.

13. Mendel’s Genetics
• With all of the seven pea plant
traits that Mendel examined, one
form appeared dominant over
the other, which is to say it
masked the presence of the other
allele.
• For example, when the genotype
for pea seed color is YG
(heterozygous), the phenotype is
yellow. However, the dominant
yellow allele does not alter
the recessive green one in any
way.
• Both alleles can be passed on to
the next generation unchanged.

14. Mendel’s Genetics
• Mendel's observations from
these experiments can be
summarized in two
principles:
1) the principle of segregation
2) the principle of
independent assortment

15. Segregation
• for any particular trait,
the pair of alleles of each
parent separate and only
one allele passes from
each parent on to an
offspring. Which allele in
a parent's pair of alleles is
inherited is a matter of
chance.
• this segregation of alleles (Segregation of alleles in the production
occurs during the process of sex cells)
of sex cell formation

16. Independent Assortment
• Independent
assortment answers the
question of what
happens when two
parent cells differ in two
or more genes
• Mendel discovered
independent
assortment when he
performed experiments
called dihybrid crosses

17. Independent Assortment
• alleles of different genes
assort independently from one
another during gamete
formation
• happens when genes are on
different chromosomes
• does not hold true for genes
that are on that same
chromosome because if two
genes are close enough
together on the same
chromosome then they may
be linked in which case they
stay together while crossing
over. This phenomenon is
called linkage

18. References:
• http://www.monteweston.com/Biology/Jasm10.html
• http://www.google.com.ph/search?tbm=isch&hl=en&source=hp&biw=1366&bih=610&q=indepen
dent+assortment&gbv=2&oq=independent+a&aq=0&aqi=g10&aql=&gs_sm=1&gs_upl=1219l6097l
0l7772l13l13l0l5l5l0l63l349l8l8l0
• http://www.google.com.ph/search?tbm=isch&hl=en&source=hp&biw=1366&bih=653&q=gregor+
mendel&gbv=2&oq=gregor+men&aq=0&aqi=g10&aql=&gs_sm=1&gs_upl=645l3132l0l4935l10l10l
0l2l2l0l97l476l8l8l0#hl=en&gbv=2&tbm=isch&sa=1&q=law+of+segregation&pbx=1&oq=law+og+se
&aq=0sS&aqi=g-
sS1&aql=&gs_sm=3&gs_upl=953646l957289l8l959174l13l13l2l0l0l0l184l990l7.4l11l0&bav=on.2,or.
r_gc.r_pw.r_qf.,cf.osb&fp=3f24af890326a12a&biw=1366&bih=610
• http://anthro.palomar.edu/mendel/mendel_1.htm
• http://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel1.htm
• http://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel3.htm
• http://www.google.com.ph/search?tbm=isch&hl=en&source=hp&biw=1366&bih=653&q=gregor+
mendel&gbv=2&oq=gregor+men&aq=0&aqi=g10&aql=&gs_sm=1&gs_upl=645l3132l0l4935l10l10l
0l2l2l0l97l476l8l8l0#hl=en&gbv=2&biw=1366&bih=610&tbm=isch&sa=1&q=pea+&pbx=1&oq=pea
+&aq=f&aqi=g10&aql=&gs_sm=3&gs_upl=2403l2403l15l2724l1l1l1l0l0l0l0l0ll0l0&bav=on.2,or.r_gc
.r_pw.r_qf.,cf.osb&fp=3f24af890326a12a