Transcript Gregor Mendel and Basic Genetic Principles

Gregor Mendel
&
Basic Genetic Principles
Who is Gregor Mendel?
• Austrian Monk that experimented with pea
plants.
• He discovered the basic principles of
genetics.
Pea Plants
• Pollination occurs easily within the flower.
• Relatively short life cycle (2-3 weeks).
• Have 7 characteristics with contrasting
forms.
Pollination
• Movement of pollen between sexual parts
of flowers.
• Self Pollination – pollination that occurs
within one flower.
• Cross Pollination – movement of pollen
from one flower to another.
7 different traits of pea plants
• Seed shape –
round/wrinkled
• Seed color –
yellow/green
• Seed coat color –
colored/white
• Pod shape –
inflated/constricted
• Pod color –
green/yellow
• Flower position –
axial/terminal
• Stem length –
long/short
Mendel’s 1st Experiment
• Mendel created pure–bred pea plants of
each characteristic.
Ex. Tall/Short, Green seeds/Yellow seeds.
• He crossed these plants together
(P1 or Parent generation).
• Offspring: ALL TALL! (F1 generation).
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1
Mendel’s
Law
Law of Dominance
• When organisms with contrasting traits are
crossed, only the Dominant trait appears
in the offspring.
Mendel’s 2nd Experiment
• Mendel took those F1 generation plants
and crossed them.
• F2 generation results: 3 TALL, 1 SHORT =
3:1 phenotypic ratio.
• 1 TT, 2 Tt, 1 tt =1:2:1 genotypic ratio
Mendel’s 2nd Law
Law of Segregation
• Factors occur in pairs and separate during
gamete formation only to recombine again
during fertilization.
Vocabulary
• Dominant gene – gene that prevents the
expression of another. Ex. Brown hair –
represented with a capital B.
• Recessive gene – gene that is not
expressed, it is usually hidden by a
dominant gene. Ex. Blond hair –
represented with a lower case b.
• Allele – dominant and recessive forms of
genes.
• Genotype – genetic makeup of an
organism regarding its characteristics.(TT,
Tt, tt)
• Phenotype – physical appearance of an
organism. (Tall/Short)
• Heterozygous – have 2 different alleles for a
particular charateristic. (Ex. Tt = a heterozygous
tall plant)
• Homozygous – have the same alleles for a
particular characteristic. (Ex. TT = a
homozygous tall plant & tt = a homozygous short
plant)
• Hybrid – Common term for heterozygous. Ex. Tt
• Monohybrid Cross – Cross between two
parents that deals with only one trait.
• Dihybrid Cross – Cross between two
parents dealing with two different traits.
• Incomplete dominance – Blending, when
both traits express themselves.
• Sex linked traits – Involves genes that
are located on the X chromosome.
figure 10-13.jpg
Figure
10.13
Figure 10.13
Mendel's law of independent
assortment of alleles
• Alleles of different genes are assorted
independently of one another during the
formation of gametes.
• Mendel determined this law by crossing plants
containing two different traits. (Ex. True breed
round & yellow seeded plants (RRYY) with true
breed wrinkled & green seeds (rryy)
figure 10-07.jpg
Figure
10.7
Figure 10.7