Transcript Why Pea Plants? - New Century Academy

Chapter 14: Menelian Genetics
Objectives
1.
Understand the two laws Mendel came up with
2.
Understand the laws of probability associated with
Mendalian Genetics
3.
You will know that inheritance is more complicated then
what Mendel predicted
4.
Many human traits follow Mendelian Genetics patterns
Why Pea Plants?
1.
Peas have different characters or
traits like color that were distinct
2.
Short generations
3.
Large number of offspring
4.
Could control pollination
5.
Picked true breeding plants (All selfpollinated offspring have same traits)
6.
He could cross pollinate or hybridize
two true breeding parental
generations
7.
He could gather good data on the
First and second generations
Conclusion 1.
Traits occur in different versions
called alleles
Mendel’s
Conclusions
Conclusion 2.
An organism inherits one allele from
mom and one from dad.
Conclusion 4.
“Law of
Segregation”
Two alleles segregate
separately during
meiosis into different
haploid sex cells.
Conclusion 3.
Alleles can be either dominant or
recessive with the recessive only being
expressed in a homozygous
“Law of Independent
Assortment”
-Pairs of alleles or genes
segregate independently from
other allele pairs
-Law doesn’t apply to genes
that are located near each
other on the same
chromosome
Probability
Complex Genetics Problems use both
multiplication and addition
Monohybrid Cross = one
character
Hair Color
1.
Genotypic
Ratios
A
a
A
AA
Aa
Aa = 2/4
a
Aa
aa
aa = ¼
AA = ¼
Use multiplying ratios
or the punnet square
Pp = ___/4
Eye Color
b
b
B
b
Bb
bb
Bb
bb
Three characters (Flower color, Seed color, and
Pod shape) are considered in a cross between
two pea plants (PpYyIi X ppYyii) What fraction
of offspring would be predicted to be homozygous
recessive for at least two of the three characters
Genotypic
pp = ___/4
Possible
Genotypes
Ratios
YY = ___/4
1.
Yy = ___/4
2.
BB = 0
yy = ___/4
3.
Bb = 2/4
Ii = ___/4
4.
bb = 2/4
Ii = ___/4
5.
1.
What is the probability of getting an offspring that is
homozygous recessive for both traits?
2.
What is the probability of getting an offspring that expresses
both dominant phenotypes?
Trihybrid Cross
Multiplication Rule: States multiplication is used to determine the probability of two or
more independent events will occur at the same time
Addition Rule: States addition is used to determine the probability of one of two or
more events occuring.
Complex Inheritance Patterns
1.
Degrees of Dominance (Read p. 272 “Relationship
between…”)
a.
Complete (Normal Dominant vs Recessive)
b.
Incomplete (Heterozygous and neither allele is
completely dominant
c.
Codominance (Both alleles are expressed
equally)
2.
Multiple alleles
3.
Pleiotropy – Gene codes for more then one
phenotype
4.
Two or more genes code for same phenotype
Multiple genes coding for one trait
Polygenic Inheritance
Epistasis
- One gene can alter the expression
of other genes
-Quantitative characters or amount of alleles determines
color