The individuals of every population have a variety of phenotypes. These variations are a result of genotypic variance caused by the inheritance of different alleles. The presence or absence of an allele inherited according to the Mendelian laws of inheritance can be followed through many generations with a pedigree chart.
In this activity you will identify your phenotype for eight characteristics and use these observations to try to determine the associated genotypes. Then you and a partner will determine the phenotypes and genotypes for possible first- and second-generation offspring and construct a pedigree chart.
Purpose
To determine your phenotype and genotype for a characteristic and to track allele inheritance through three generations
Equipment and Materials
- coin
Procedure
SKILLS HANDBOOK A2.4
Part A: Determining Your Genotype
1. Copy Table 1 into your notebook.
Table 1 Genotypes for Some Common Human Phenotypes
Characteristic: tongue roll Dominant phenotype: roller (R) Recessive phenotype: non-roller (r) Characteristic: thumb flexibility Dominant phenotype: bent back (T) Recessive phenotype: straight (t)
Characteristic: thumb placement with hands clasped Dominant phenotype: left thumb on top (P) Recessive phenotype: right thumb on top (p)
2. Using the information in Table 1 as a guide, draw and complete a data table similar to Table 2 that lists all eight characteristics. If, for a particular trait, you do not know whether you are homozygous dominant or heterozygous, record your genotype as heterozygous.
Table 2 Determining Your Genotype
Characteristic: dimples Phenotype: Possible genotype(s):
Characteristic: earlobes Phenotype: Possible genotype(s):
Part B: The F1 Generation
Now you will work with a partner to simulate the passing on of genetic information to a single offspring. For this activity, ignore sex.
3. Copy Table 3 into your notebook, with rows for all eight characteristics.
4. To determine the genetic makeup of the offspring, you and your partner (parent 1 and parent 2) must each contribute a single allele for each characteristic. To choose each allele, you must make eight coin flips—one for each characteristic. If you flip "heads," you contribute the first allele of your genotype; if you flip "tails," you contribute the second allele. For example, if you flip heads for "thumb flexibility" and you are Tt, then you enter T under your parent column in Table 3.
5. After you have determined the alleles for each characteristic, complete the genotype and phenotype columns in your table.
Table 3 Genotype and Phenotype of F1-Generation Offspring
Characteristic: dimples Allele from parent 1: Allele from parent 2: Genotype: Phenotype:
Characteristic: earlobes Allele from parent 1: Allele from parent 2: Genotype: Phenotype:
Print Page 217
Part C: The F2 Generation
Now you will simulate the mating of your offspring with the offspring of another pair of students.
6. Repeat Step 4 to model the contribution of alleles from the two F1 offspring and determine the genotype and phenotype of their F2 offspring—your "grandchild" in this simulation. Record your data in a new copy of Table 3 titled "Genotype and Phenotype of F2-Generation Offspring."
7. Choose any single trait in your grandchild and track its inheritance over the three generations.
Key
K/U: Knowledge and Understanding T/I: Thinking and Investigation C: Communication A: Application
Analyze and Evaluate
(a) In this activity, which step(s) represent(s) an event in meiosis? Is this a true representation? Why or why not? T/I
(b) Use examples from the activity to explain your understanding of the terms "genotype," "phenotype," ‘`recessive," and "dominant." T/I C
The individuals of every population have a variety of phenotypes. These variations are a result of genotypic variance caused by the inheritance of different alleles. The presence or absence of an allele inherited according to the Mendelian laws of inheritance can be followed through many generations with a pedigree chart.
In this activity you will identify your phenotype for eight characteristics and use these observations to try to determine the associated genotypes. Then you and a partner will determine the phenotypes and genotypes for possible first- and second-generation offspring and construct a pedigree chart.
Purpose
To determine your phenotype and genotype for a characteristic and to track allele inheritance through three generations
Equipment and Materials
- coin
Procedure
SKILLS HANDBOOK A2.4
Part A: Determining Your Genotype
1. Copy Table 1 into your notebook.
Table 1 Genotypes for Some Common Human Phenotypes
Characteristic: dimples
Dominant phenotype: present (D)
Recessive phenotype: absent (d)
Characteristic: earlobes
Dominant phenotype: freely hanging (F)
Recessive phenotype: attached (f)
Characteristic: hair on mid-finger
Dominant phenotype: hair present (H)
Recessive phenotype: hair absent (h)
Characteristic: 2nd toe longer than big toe
Dominant phenotype: longer (L)
Recessive phenotype: shorter (l)
Characteristic: hairline
Dominant phenotype: widows peak (W)
Recessive phenotype: straight (w)
Characteristic: tongue roll
Dominant phenotype: roller (R)
Recessive phenotype: non-roller (r)
Characteristic: thumb flexibility
Dominant phenotype: bent back (T)
Recessive phenotype: straight (t)
Characteristic: thumb placement with hands clasped
Dominant phenotype: left thumb on top (P)
Recessive phenotype: right thumb on top (p)
2. Using the information in Table 1 as a guide, draw and complete a data table similar to Table 2 that lists all eight characteristics. If, for a particular trait, you do not know whether you are homozygous dominant or heterozygous, record your genotype as heterozygous.
Table 2 Determining Your Genotype
Characteristic: dimples
Phenotype:
Possible genotype(s):
Characteristic: earlobes
Phenotype:
Possible genotype(s):
Part B: The F1 Generation
Now you will work with a partner to simulate the passing on of genetic information to a single offspring. For this activity, ignore sex.
3. Copy Table 3 into your notebook, with rows for all eight characteristics.
4. To determine the genetic makeup of the offspring, you and your partner (parent 1 and parent 2) must each contribute a single allele for each characteristic. To choose each allele, you must make eight coin flips—one for each characteristic. If you flip "heads," you contribute the first allele of your genotype; if you flip "tails," you contribute the second allele. For example, if you flip heads for "thumb flexibility" and you are Tt, then you enter T under your parent column in Table 3.
5. After you have determined the alleles for each characteristic, complete the genotype and phenotype columns in your table.
Table 3 Genotype and Phenotype of F1-Generation Offspring
Characteristic: dimples
Allele from parent 1:
Allele from parent 2:
Genotype:
Phenotype:
Characteristic: earlobes
Allele from parent 1:
Allele from parent 2:
Genotype:
Phenotype:
Print Page 217
Part C: The F2 Generation
Now you will simulate the mating of your offspring with the offspring of another pair of students.
6. Repeat Step 4 to model the contribution of alleles from the two F1 offspring and determine the genotype and phenotype of their F2 offspring—your "grandchild" in this simulation. Record your data in a new copy of Table 3 titled "Genotype and Phenotype of F2-Generation Offspring."
7. Choose any single trait in your grandchild and track its inheritance over the three generations.
Key
K/U: Knowledge and Understanding
T/I: Thinking and Investigation
C: Communication
A: Application
Analyze and Evaluate
(a) In this activity, which step(s) represent(s) an event in meiosis? Is this a true representation? Why or why not? T/I
(b) Use examples from the activity to explain your understanding of the terms "genotype," "phenotype," ‘`recessive," and "dominant." T/I C