Question

practice: alleles, dominant, recessive, genotype, phenotype
instructions: answer each of the following questions using what we learned in the first 2 days of this unit.

1. for each example below, identify whether it is an example of a genotype or a phenotype.

bb
brown eyes
homozygous recessive
short hair
aa
heterozygous
ww
tall
5 fingers
hh
homozygous dominant
black fur

1. for each of the examples below, use the provided alleles to determine what the offspring will look like.

t = tall	t = short	b= brown eyes	b= blue eyes
g= green scales	g = blue scales	e= detached ear lobe	e = attached ear lobe
l= long eyelashes	l = short eyelashes	d= dimples	d = no dimples
s= no spots	s= spots

a. offspring = tt
b. offspring = gg
c. offspring = ll
d. offspring = ss
e. offspring = bb
f. offspring = ee
g. offspring = dd

1. for each example, write all possible genotypes that could result in the given appearance.

a. phenotype = no spots \tgenotype =
b. phenotype = blue eyes \tgenotype =
c. phenotype = tall \t\tgenotype =
d. phenotype = no dimples \tgenotype =
e. phenotype = green scales \tgenotype =

Answer:

Question 1 Solutions:

To determine if an example is a genotype or phenotype, recall:

• Genotype: Genetic makeup (allele combinations, e.g., \( BB \), \( ww \), \( Aa \)).
• Phenotype: Physical/trait expression (e.g., “Brown eyes,” “Tall,” “Short hair”).

Example	Classification	Reason
\( ww \)	Genotype	Allele combination.
Brown eyes	Phenotype	Physical trait (eye color).
Tall	Phenotype	Physical trait (height).
Homozygous recessive	Genotype	Describes allele combination.
5 fingers	Phenotype	Physical trait (digit count).
Short hair	Phenotype	Physical trait (hair length).
\( Hh \)	Genotype	Allele combination.
\( Aa \)	Genotype	Allele combination.
Homozygous dominant	Genotype	Describes allele combination.
Heterozygous	Genotype	Describes allele combination.
Black fur	Phenotype	Physical trait (fur color).

Question 2 Solutions:

Use the allele key (e.g., \( T = \text{tall} \), \( t = \text{short} \)) to determine the phenotype from the genotype:

Offspring Genotype	Phenotype (Trait)	Reason (Allele Key)
\( \text{b. } Gg \)	Green scales	\( G = \text{green scales} \) (dominant allele expressed).
\( \text{c. } LL \)	Long eyelashes	\( L = \text{long eyelashes} \), homozygous dominant.
\( \text{d. } ss \)	Spots	\( s = \text{spots} \), homozygous recessive.
\( \text{e. } Bb \)	Brown eyes	\( B = \text{brown eyes} \) (dominant allele expressed).
\( \text{f. } ee \)	Attached ear lobe	\( e = \text{attached ear lobe} \), homozygous recessive.
\( \text{g. } DD \)	Dimples	\( D = \text{dimples} \), homozygous dominant.

Question 3 Solutions:

To find possible genotypes for a phenotype, use dominance rules (dominant allele masks recessive):

Phenotype	Possible Genotypes	Reason (Allele Key)
\( \text{b. Blue eyes} \)	\( bb \)	\( b = \text{blue eyes} \) (recessive). Only \( bb \) (homozygous recessive) shows blue eyes (dominant \( B \) masks \( b \)).
\( \text{c. Tall} \)	\( TT \), \( Tt \)	\( T = \text{tall} \) (dominant). \( TT \) (homozygous) or \( Tt \) (heterozygous) express “Tall” (recessive \( t \) is masked).
\( \text{d. No dimples} \)	\( dd \)	\( d = \text{no dimples} \) (recessive). Only \( dd \) (homozygous recessive) shows no dimples (dominant \( D \) masks \( d \)).
\( \text{e. Green Scales} \)	\( GG \), \( Gg \)	\( G = \text{green scales} \) (dominant). \( GG \) (homozygous) or \( Gg \) (heterozygous) express “Green Scales” (recessive \( g \) is masked).

Final Answers (Summarized):

Question 1:

• \( BB \): Genotype
• \( ww \): Genotype
• Brown eyes: Phenotype
• Tall: Phenotype
• Homozygous recessive: Genotype
• 5 fingers: Phenotype
• Short hair: Phenotype
• \( Hh \): Genotype
• \( Aa \): Genotype
• Homozygous dominant: Genotype
• Heterozygous: Genotype
• Black fur: Phenotype

Question 2:

• a. \( tt \): Short
• b. \( Gg \): Green scales
• c. \( LL \): Long eyelashes
• d. \( ss \): Spots
• e. \( Bb \): Brown eyes
• f. \( ee \): Attached ear lobe
• g. \( DD \): Dimples

Question 3:

• a. No Spots: \( SS \), \( Ss \)
• b. Blue eyes: \( bb \)
• c. Tall: \( TT \), \( Tt \)
• d. No dimples: \( dd \)
• e. Green Scales: \( GG \), \( Gg \)