Transcript Mendel`sWork

Gregor Mendel
• Modern genetics had its beginnings in an abbey
garden, where a monk named Gregor Mendel was
first to figure out basic patterns of inheritance.
• He did so by breeding garden peas in carefully
planned experiments.
The work of Gregor Mendel
• Previous views of
Inheritance
– Blending
– Spermists
– Ovists
“Father of Genetics”
• Mendel’s mathematical
patterns were not
appreciated until 1900,
16 years after his death
• 1920s: Meiosis
• 1950s: Structure of DNA
• 1960s: Protein Synthesis
• 1990s: Genome Project
Genetic crosses
• To hybridize 2 varieties
of pea plants, Mendel
used an artist’s brush.
• He transferred pollen
from a true breeding
white flower to the
carpel of a true breeding
purple flower.
Pea Traits in Greg’s Garden
•
•
•
•
•
•
•
•
Flower Position
Plant height
Pod appearance
Pod appearance
Pod color
Seed Texture
Seed Color
Sead coat color
Interpreting Mendel’s Data
Parent
Cross
1st (F1)
generation
next (F2)
generation
Round x 100% round 5,474 round
wrinkled
1,850 wrink.
Yellow x
green pea
100%
yellow
6,022 yell
2,001 green
Long x
short
stem
100% long
stem
787 long
277 short
Interpreting Mendel’s Data
Parent
Cross
1st (F1)
generation
next (F2) Actual Probability
generation Ratio
Ratio
Round x 100% round 5,474 round 2.96:1
wrinkled
1,850 wrink.
3:1
Yellow x
green pea
100%
yellow
3:1
Long x
short
stem
100% long
stem
6,022 yell 3.01:1
2,001 green
787 long
277 short
2.84:1
3:1
Tracking heritable characteristics
• Mendel tracked
heritable characters
for 3 generations.
• When F1 hybrids were
allowed to selfpollinate a 3:1 ratio of
the 2 varieties
occurred in the F2
generation.
Mendel’s law of segregation
• By carrying out these
monohybrid crosses,
Mendel determined that
the 2 alleles for each
character segregate during
gamete production.
Mendel’s Observations
• “dominant” vs “recessive”
• Before “genes” and “meiosis” was thought
of, Mendel theorized that “inheritance
factors”…
– are in the pollen and ova of peas as alternate
forms for different traits.
– occur in pairs, (equal contribution from both
parents)
– separate during gamete formation and pair up
again at fertilization
Mendel’s Law of Segregation
• Each hereditary characteristic is
controlled by two factors (alleles) that
separate and pass into reproductive cells
(gametes).
Mendel’s Law of Independent
Assortment
• Pairs of inheritance factors (alleles)
segregate independently of each other
when sex cells (gametes) are formed.
Mendelian Inheritance in Humans
dominant
recessive
•
•
•
•
Tongue Roller (T)
Free Earlobes (F)
Dimples (D)
Widow’s Peak (P)
•
•
•
•
Can’t roll tongue (t)
Attached lobes (f)
No dimples (d)
Straight hairline (w)
Some Vital Vocab.
•
•
•
•
•
Genetics
Genotype vs Phenotype
DNA, Chromosome, Gene
Alleles (Dominant vs Recessive)
Allele Combinations:
– Homozygous
– Heterozygous