I

Assignment No 1:

BIO 301

D: MC170404186

Q1: What are the phenotypic and genotypic ratios in
Mendel Law of Independent assortment?

Answer:

                  Genotype
is the genetic makeup of an organism that include number of chromosomes, number
of genes, the sequence of genes or the inheritance pattern of an organism. They
are expressed in a pair of letters, usually which are alleles. The alleles pairs
genotype is commonly expressed as RR (each letter representing one allele) as a
dominant trait, Rr as co-dominant or as recessive. This example uses the letter
R, but difference letters are used to describe different traits. They are
actual fact just variables.

Phenotype is the physical appearance of an organism. Like the height of an
organism. The color of the skin or the color of eyes. The phenotype includes
physical characteristics behavior corres-ponding to such species, structures,
organs, behaviors reflexes etc.

Example: 
Let’s BB or Bb is the coding for black hair. BB/Bb is the genotype and
the black hair is the phenotype.

According to Mendel Law of
independent assortment

Examples: Dihybrid cross, true breeding plants for two traits. For
example, a plant that had green pod color and yellow seed color was
cross-pollinated with a plant that had yellow pod color and green seeds.

The traits for green pod color (GG) and yellow seed color (YY) are
dominanat. Yellow pod color (gg) and green seed color (yy) are recessive. F1
plants heterozygous GgYy.

F1 plants                                                                                          

True breeding                         
True breeding yellow                              All green
pods         

Green pods with          x          pods with green                     =                with yellow seeds

Yellow seeds                             seeds

GGYY                                         
ggyy                                                                   
GgYy

 

After observing the resuts of dihybrid cross, Mendel allowed all of the F1
plants to self pollinate.He reffered to these offspring as F2 generation.
Mendel noticed the 9:3:3:1 ratio.

 

                                                 
F1 GgYy

                                           

 
 

 
GY

 
Gy

 
gY

 
gy

 
GY

 
GGYY

 
GGYy

 
GgYY

 
GgYy

 
Gy
 

 
GGYy

 
GGyy

 
GgYy

 
Ggyy

 
gY

 
GgYy

 
GgYy

 
ggYY

 
ggYy

 
gy

 
GgYy

 
Ggyy

 
ggYy

 
ggyy

F1 GgYy

                           9:3:3:1
ratio.              

                

Phenotypic ratio is 9:3:3:1.

Genotypic ratio is 1/16 (GGYY)
+2/16(Ggyy)+2/16(GgYy)+1/16(GGyy)+1/16(ggYY) + 4/16
(GgYy)+2/16(ggyy)+2/16(ggYy)+ 1/16(ggyy).