Transcript Chapter: 9 Fundamentals of Genetics

Chapter: 9 Fundamentals
of Genetics
Objectives
Describe how Mendel was able to control how his pea
plants were pollinated.
Describe the steps in Mendel’s experiments on truebreeding garden peas.
Distinguish between dominant and recessive traits.
State two laws of heredity that were developed from
Mendel’s work.
Describe how Mendel’s results can be explained by
scientific knowledge of genes and chromosomes.
I. Father of Genetics
A. Gregor Mendel
Austrian Monk
B. Knowledge of statistics helped him with
heredity
A.
A.
Heredity = the transmission of
characteristics from parents to offspring.
II. Mendel’s Legacy
A. Observed 7 traits (a genetically
determined variant of a characteristic) of
Garder Peas
A.
B.
C.
D.
E.
F.
G.
Height
Flower position
Pod color
Pod appearance
Seed texture
Seed color
Flower color
III. Mendel’s Methods
A. Pollination
Male parts combine with female parts
in plants
B. Self-pollination = male parts combine
with female parts of same plants
C. Cross pollination = male parts combine
with female parts of different plants
A.
IV. Mendel’s Experiments
A. Crossed the P generation
A.
These were plants that each had a specific
traits (ex: purple flowers and white flowers)
B. Mendel got his first F generation
A.
B.
He used the symbol F1
All flowers were purple
C. Mendel then crossed two from F1
generation to get F2 generation.
A.
He got 3 purple flowers and 1 white flowers.
V. Mendel’s Results
A.
B.
Traits were observed based on dominant factors
and recessive factors.
Dominant factor – the trait that appears even if a
recessive trait is present
A.
B.
C.
Recessive factor – can only be observed when it
is paired with another recessive factor
A.
B.
D.
Always shown as a capital letter
B
Always shown as a lowercase letter
b
The trait that masked the other was called the
dominant trait. The trait that was masked was
called the recessive trait.
VI. Law of Segregation
A. Factors that control traits are
separated during the formation of
gametes.
VII. Law of Independent
Assortment
A. Dominant factors of one trait are not
always paired with dominant factors
of different traits.
A.
Ex: You could be dominant for seed
color but recessive for flower color
VIII. Support for Mendel’s
Conclusions
We now know that the factors that
Mendel studied are alleles, or
alternative forms of a gene.
One allele for each trait is passed
from each parent to the offspring.
IX. Genetic Crosses
A. Genotype – an organism’s genetic make
up.
A.
The letters (BB, Bb, or b,b)
B. Phenotype – the appearance of the trait
A.
Ex. Purple flowers
C. Probability – likelihood a specific event
will occur
A.
A probability may be expressed as a decimal,
a percentage, or a fraction.
X. Predicting Results of Monohybrid Crosses
A. Cross in which only 1 characteristic is
tracked.
B. A Punnett square can be used to predict
the outcome of genetic crosses.
C. Homozygous – same genotype alleles
Ex. BB or bb
D. Heterozygous – one dominant allele and
one recessive allele
Ex. Bb
XI. Homozygous dominant x
Homozygous recessive
Purple is dominant over white
PP (purple) x pp (white)
p
p
Genotypic ratio = 4:0
P
P p
P
P p
P p
P
p
Phenotypic ratio = 4
purple : 0 white
XII. Homozygous dominant x
heterozygous
Purple is dominant over white
PP (purple) x Pp (purple)
P
p
p
Genotypic ratio = 2:2
P
P P
P
P P
P p
P
p
Phenotypic ratio = 4
purple : 0 white
XIII. heterozygous x heterozygous
Purple is dominant over white
Pp (purple) x Pp (purple)
p
P
Genotypic ratio = 1:3:1
P
P P
p
P p
P p
p
p
Phenotypic ratio = 3
purple : 1 white
XIV. Incomplete dominance
In roses (R = red,
Rr = pink, rr =
white)
r
R
Genotypic ratio = 1:3:1
R
P
r
R R
R r
R r
r
r
Phenotypic ratio = 1 red:
2 pink: 2 white
XV. Co-Dominance
In guinea pigs (B = black, Bb = black and white, bb = white)