Question

how can you determine the recombination frequencies for each pair of genes? the a and b genes are used as an example.
match the terms in the left column to the appropriate blanks in the sentences on the right. terms can be used once, more than once, or not at all.

1. obtain parental flies, one with dominant alleles of the two genes ( ) and the second with recessive alleles ( ).
2. breed this pair of dihybrid generation flies and obtain an
3. testcross the obtained dihybrid with a doubly ( )
4. class the offspring as parental or recombinant, based on the genotypes of the generation.
5. add up the number of ( ) types and then ( ) by the total number of offspring.

Explanation:

To solve this problem, we analyze each step of determining recombination frequencies for a pair of genes (A and B) using the given terms:

Step 1: Obtain Parental Flies

We need two parental flies: one with dominant alleles (homozygous dominant, e.g., \( AABB \)) and one with recessive alleles (homozygous recessive, e.g., \( aabb \)).

Step 2: Breed the Parental Pair

Breed the \( P \)-generation (parents: \( AABB \) and \( aabb \)) to obtain the \( F_1 \)-generation. The \( F_1 \) offspring will be heterozygous (e.g., \( AaBb \)), as they inherit one dominant and one recessive allele for each gene.

Step 3: Testcross the \( F_1 \) Dihybrid

Testcross the \( F_1 \) dihybrid (\( AaBb \)) with a doubly homozygous recessive fly (\( aabb \)). This cross helps identify recombinant vs. parental offspring.

Step 4: Classify Offspring

Classify \( F_2 \) offspring as parental (genotype matches parents, e.g., \( AABB \) or \( aabb \)) or recombinant (new genotype, e.g., \( AaBB \) or \( Aabb \)) based on their genotypes.

Step 5: Calculate Recombination Frequency

Add the number of recombinant offspring and divide by the total number of \( F_2 \) offspring. The formula is:

$$ \text{Recombination Frequency} = \frac{\text{Number of Recombinant Offspring}}{\text{Total Number of Offspring}} \times 100\% $$

Matching Terms to Blanks (Example)

1. Obtain \(\boldsymbol{\text{parents}}\) (parental flies: \( AABB \) and \( aabb \)).
2. Breed this pair of \(\boldsymbol{\text{parents}}\) ( \( P \)-generation) to obtain an \(\boldsymbol{F_1}\) (dihybrid: \( AaBb \)).
3. Testcross the obtained dihybrid with a doubly \(\boldsymbol{\text{homozygous recessive}}\) fly (\( aabb \)).
4. Class the offspring as parental or recombinant, based on the genotypes of the \(\boldsymbol{P}\) (parental) generation.
5. Add up the number of \(\boldsymbol{\text{recombinant}}\) offspring and divide by the total number of \(\boldsymbol{\text{offspring}}\).

Final Answer (Term Matching)

1. parents
2. parents; \( F_1 \)
3. homozygous recessive
4. \( P \)
5. recombinant; offspring

Answer:

To solve this problem, we analyze each step of determining recombination frequencies for a pair of genes (A and B) using the given terms:

Step 1: Obtain Parental Flies

We need two parental flies: one with dominant alleles (homozygous dominant, e.g., \( AABB \)) and one with recessive alleles (homozygous recessive, e.g., \( aabb \)).

Step 2: Breed the Parental Pair

Breed the \( P \)-generation (parents: \( AABB \) and \( aabb \)) to obtain the \( F_1 \)-generation. The \( F_1 \) offspring will be heterozygous (e.g., \( AaBb \)), as they inherit one dominant and one recessive allele for each gene.

Step 3: Testcross the \( F_1 \) Dihybrid

Testcross the \( F_1 \) dihybrid (\( AaBb \)) with a doubly homozygous recessive fly (\( aabb \)). This cross helps identify recombinant vs. parental offspring.

Step 4: Classify Offspring

Classify \( F_2 \) offspring as parental (genotype matches parents, e.g., \( AABB \) or \( aabb \)) or recombinant (new genotype, e.g., \( AaBB \) or \( Aabb \)) based on their genotypes.

Step 5: Calculate Recombination Frequency

Add the number of recombinant offspring and divide by the total number of \( F_2 \) offspring. The formula is:

$$ \text{Recombination Frequency} = \frac{\text{Number of Recombinant Offspring}}{\text{Total Number of Offspring}} \times 100\% $$

Matching Terms to Blanks (Example)

1. Obtain \(\boldsymbol{\text{parents}}\) (parental flies: \( AABB \) and \( aabb \)).
2. Breed this pair of \(\boldsymbol{\text{parents}}\) ( \( P \)-generation) to obtain an \(\boldsymbol{F_1}\) (dihybrid: \( AaBb \)).
3. Testcross the obtained dihybrid with a doubly \(\boldsymbol{\text{homozygous recessive}}\) fly (\( aabb \)).
4. Class the offspring as parental or recombinant, based on the genotypes of the \(\boldsymbol{P}\) (parental) generation.
5. Add up the number of \(\boldsymbol{\text{recombinant}}\) offspring and divide by the total number of \(\boldsymbol{\text{offspring}}\).

Final Answer (Term Matching)

1. parents
2. parents; \( F_1 \)
3. homozygous recessive
4. \( P \)
5. recombinant; offspring