investigation 9.3
TRANSCRIPT
The inherited information is located in the nucleusnucleus of every cell in the organism. The information is coded in the huge DNADNA molecule. The huge molecules are coiled into compact hot dog-shaped structures called chromosomeschromosomes. ChromosomesChromosomes are always present in
almost identical pairs. Locations on chromosomes that affect features of organisms are called allelesalleles. A gene is composed of 2 alleles2 alleles. An organism's unique
combination of genes is its genotypegenotype. The traits produced by an organism’s genes is its phenotypephenotype.
Alleles that have more influence in determining traits are dominantdominant alleles. Alleles that have less influence
in determining traits are recessiverecessive alleles.
CHROMOSOME
GENE
NUCLEUS
ALLELE
HOMOZYGOUSHOMOZYGOUS• 2 identical alleles
–Homozygous dominant – AA
–Homozygous recessive - aa
HETEROZYGOUSHETEROZYGOUS
• 2 different alleles–Aa
–Phenotype is like dominant allele
Trait Dominant Allele
Recessive Allele
Body Shape
Squarepants (S)
Roundpants (s)
Body Color Yellow (Y) Blue (y)
Eye Shape Round (R) Oval (r)
Nose Style Long (L) Stubby (l)Genotype Phenotype Genotype Phenotype
LL Rr
yy ll
Ss ss
RR Yy
Trait Dominant Allele
Recessive Allele
Body Shape
Squarepants (S)
Roundpants (s)
Body Color Yellow (Y) Blue (y)
Eye Shape Round (R) Oval (r)
Nose Style Long (L) Stubby (l)Genotype Phenotype Genotype Phenotype
Yellow Body
Stubby Nose
Roundpants
Round eyes
Oval Eyes Squarepants
Long nose Blue Body
Trait Dominant Allele
Recessive Allele
Body Shape
Squarepants (S)
Roundpants (s)
Body Color Yellow (Y) Blue (y)
Eye Shape Round (R) Oval (r)
Nose Style Long (L) Stubby (l)•Heterozygous round eyes
•Homozygous long nose
•Purebred squarepants
•Hybrid yellow body
Sponge Bob gets Sponge Bob gets married!married!
• SpongeBob’s Genotype– SS– YY– RR– LL
• SpongeSusie’s Genotype– ss– yy– rr– ll
What will Junior look like?
• Junior gets ½ of his genes from mom and ½ from Dad
• Dad is Homozygous Dominant for all traits
• Mom is Homozygous Recessive for all traits
Dad MomS
Y
R
L
s
y
r
l
Reflection page 76
Record Junior’s phenotype and
genotype