1. Today you will need: Your journal The handout as you come in (QUIZ)
Welcome Back!!!
Today you will need:
Your journal
The handout as you come in (QUIZ)

3. Law of Independent Assortment
Genetics…continued…
Law of Segregation
Law of Independent Assortment
Dihybrid Crosses
Karyotyping
DNA Fingerprinting

4. The Law of Segregation and the Law of Independent Assortment

5. Law of Dominance
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.
All the offspring will be heterozygous and express only the dominant trait.
RR x rr yields all Rr (round seeds)

6. Law of Dominance

7. Independent Assortment
Segregation
Process that separates the two alleles (ex: Tt) of a gene during gamete formation (meiosis)
Independent Assortment
genes are inherited independently of each other

8. Law of Segregation
During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.
Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

9. Applying the Law of Segregation

10. Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
This law can be illustrated using dihybrid crosses.

11. Dihybrid Cross
A breeding experiment that tracks the inheritance of two traits.
Mendel’s “Law of Independent Assortment”
a. Each pair of alleles segregates independently during gamete formation
b. Formula: 2n (n = # of heterozygotes)

12. Dihybrid Cross RrGg x RrGg Traits: Seed shape & Seed colorF O I L
Traits: Seed shape & Seed color
Alleles: R round r wrinkled G green g yellow
RrGg x RrGg
RG Rg rG rg
RG Rg rG rg
All possible gamete combinations

13. Dihybrid Cross RG Rg rG rg RG Rg rG rg

14. Dihybrid Cross RG Rg rG rg Round/Green: 9 Round/yellow: 3
wrinkled/Green: 3
wrinkled/yellow: 1
RRGG
RRGg
RrGG
RrGg
RRgg
Rrgg
rrGG
rrGg
rrgg
9:3:3:1 phenotypic ratio

17. Let’s do it another way…
Rule of Multiplication:
Independent events in sequence (law of Independent Assortment)
“and”…(x)
What are the odds of flipping a coin 3 times and getting tails all 3 times?
They are ALL independent of one another…just as traits.

18. What are the odds that an offspring will be Heterozygous for two traits if the parents are both heterozygous for the same two traits?
Parents: AaBb x AaBb

19. What are the odds that an offspring will be Heterozygous for both traits if the parents genotypes are: AABb x AaBB

20. What are the odds that an offspring will be Heterozygous for 3 traits if the parents genotypes are: AabbCC x AABbcc

21. Test Cross
A mating between an individual of unknown genotype and a homozygous recessive individual.
Example: bbC__ x bbcc
BB = brown eyes
Bb = brown eyes
bb = blue eyes
CC = curly hair
Cc = curly hair
cc = straight hair bC
b___ bc

22. Test Cross Possible results: bC b___ bc bbCc C bC b___ bc bbCc bbcc or

23. Summary of Mendel’s laws
PARENT CROSS
OFFSPRING
DOMINANCE
TT x tt tall x short
100% Tt tall
SEGREGATION
Tt x Tt tall x tall
75% tall 25% short
INDEPENDENT ASSORTMENT
RrGg x RrGg round & green x round & green
9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods

24. Genetic fingerprinting13
Genetic fingerprinting
DNA analysis can be used for catching criminals, establishing
parentage, finding how closely organisms are related and many other
applications.
The pattern of bands in a gel electrophoresis is known as a
genetic fingerprint or a ‘genetic profile’
The genetic fingerprint found in a sample of blood or other tissue (containing DNA)
is then compared to other known samples to determine it’s origin…based on how similar the
banding patterns are to each other.
A DNA sample can be obtained from the suspect using blood, cheek
epithelial cells taken from the mouth lining or even the cells clinging
to the root of a hair…as long as the tissue contains DNA
Genetic fingerprinting

25. S Sample from crime scene
DNA profiles 16 V S S1 S2 S3
V Victim
S Sample from crime scene
S1 Suspect 1
S2 Suspect 2
S3 Suspect 3
More than 20 fragments
from Suspect 1 match those
taken from the crime scene

26. Paternity test 19 mother father position of restriction fragment
part of DNA strand
child
The vertical lines should not be confused with chromosomes. They each represent lengths of double-stranded DNA in a single chromosome
Child will receive one copy of the restriction fragment from the
mother and one from the father. It could be any one of these
combinations

27. There is a match between one of the child’s restriction fragments 20
Genetic fingerprint of …
1 mother
2 child
3 possible father A
4 possible father B
There is a match between one of
the child’s restriction fragments
and one of the mother’s.
There is also a match between the child’s other fragment and one from possible father A.
Neither of the child’s restriction
fragments match those of possible
father B 1 2 3 4
Starting position of sample
Paternity test

28. Picture of chromosomes arranged in pairs
Karyotype
Picture of chromosomes arranged in pairs
sex chromosomes – pair #23 that determine the sex of an individual (XX or XY)
autosomes (autosomal chromosomes) – the remaining 22 pairs of chromosomes