12. what two characters did gregor mendel study when he conducted dihybrid crosses?
a. dihybrid crosses can be used when the genes are on ______ chromosomes.
b. what was the resulting phenotypic ratio?
cross of f₁ generation
round, yellow
ry ry ry ry
ry rryy rryy rryy rryy
ry rryy rryy rryy rryy
ry rryy rryy rryy rryy
ry rryy rryy rryy rryy
non-mendelian inheritance
13. what is incomplete dominance?
a. give an example.
14. what is codominance?

Question

12. what two characters did gregor mendel study when he conducted dihybrid crosses?
a. dihybrid crosses can be used when the genes are on ______ chromosomes.
b. what was the resulting phenotypic ratio?
cross of f₁ generation
round, yellow
ry	ry	ry	ry
ry	rryy	rryy	rryy	rryy
ry	rryy	rryy	rryy	rryy
ry	rryy	rryy	rryy	rryy
ry	rryy	rryy	rryy	rryy
non-mendelian inheritance
13. what is incomplete dominance?
  a. give an example.
14. what is codominance?

Accepted Answer

### Question 12: What two characters did Gregor Mendel study when he conducted dihybrid crosses?
# Brief Explanations:
Gregor Mendel conducted dihybrid crosses to study the inheritance of two different traits simultaneously. The two characters (traits) he studied were the shape of the pea seed (round or wrinkled, determined by the gene for seed shape) and the color of the pea seed (yellow or green, determined by the gene for seed color). These traits are controlled by different genes, and his dihybrid cross experiments helped establish the law of independent assortment, which states that the alleles of two (or more) different genes get sorted into gametes independently of one another.
# Answer:
The two characters Gregor Mendel studied in his dihybrid crosses were the **shape of pea seeds** (round vs. wrinkled) and the **color of pea seeds** (yellow vs. green).

### Question 12a: Dihybrid crosses can be used when the genes are on ______ chromosomes.
# Brief Explanations:
Dihybrid crosses are used to study the inheritance of two different traits. For the law of independent assortment (which is demonstrated in dihybrid crosses) to hold, the two genes (controlling the two traits) must be located on different (non - homologous) chromosomes. If they were on the same chromosome (linked genes), they would tend to be inherited together, and the results of the dihybrid cross would not follow the typical 9:3:3:1 phenotypic ratio expected for unlinked genes. So the genes should be on non - homologous chromosomes.
# Answer:
non - homologous

### Question 12b: What was the resulting phenotypic ratio?
# Explanation:
## Step 1: Recall Mendel's dihybrid cross
Mendel's dihybrid cross involved crossing plants that were heterozygous for two traits (e.g., RrYy, where R is for round seeds, r for wrinkled; Y for yellow seeds, y for green). When these heterozygous plants are crossed (RrYy × RrYy), the possible gametes from each parent are RY, Ry, rY, and ry.
## Step 2: Analyze the Punnett square
When we create a Punnett square for this cross, we have 16 possible combinations of gametes. The phenotypic classes are:
 - Round and yellow (R_ Y_): To calculate the number of these, we consider the probability of R_ (3/4) and Y_ (3/4). So the number of round and yellow offspring is 3/4×3/4×16 = 9.
 - Round and green (R_ yy): Probability of R_ (3/4) and yy (1/4). Number of round and green offspring is 3/4×1/4×16 = 3.
 - Wrinkled and yellow (rr Y_): Probability of rr (1/4) and Y_ (3/4). Number of wrinkled and yellow offspring is 1/4×3/4×16 = 3.
 - Wrinkled and green (rr yy): Probability of rr (1/4) and yy (1/4). Number of wrinkled and green offspring is 1/4×1/4×16 = 1.
## Step 3: Determine the phenotypic ratio
The ratio of round - yellow : round - green : wrinkled - yellow : wrinkled - green is 9:3:3:1.
# Answer:
The resulting phenotypic ratio from Mendel's dihybrid cross is 9:3:3:1 (round - yellow : round - green : wrinkled - yellow : wrinkled - green).

### Question 13: What is incomplete dominance?
# Brief Explanations:
Incomplete dominance is a type of non - Mendelian inheritance. In this case, neither of the two alleles is completely dominant over the other. When an organism is heterozygous (has one copy of each allele), the phenotype is an intermediate (a blend) of the phenotypes of the two homozygous parents. For example, in snapdragons, if a red - flowered plant (homozygous for the red allele, say RR) is crossed with a white - flowered plant (homozygous for the white allele, rr), the heterozygous offspring (Rr) have pink flowers, which is an intermediate between red and white.
# Answer:
Incomplete dominance is a form of inheritance in which neither allele is completely dominant over the other, and the heterozygous phenotype is an intermediate (blended) phenotype between the two homozygous phenotypes.

### Question 13a: Give an example.
# Brief Explanations:
A classic example of incomplete dominance is seen in snapdragon flower color. When a homozygous red - flowered snapdragon (RR) is crossed with a homozygous white - flowered snapdragon (rr), the offspring (Rr) have pink flowers. The pink color is an intermediate between the red color of the RR plants and the white color of the rr plants, showing that neither the red allele nor the white allele is completely dominant, and their combined effect in the heterozygote results in a blended phenotype. Another example is in some types of coat color in horses, where a cross between a homozygous chestnut (red - brown) horse and a homozygous cremello (light cream - colored) horse produces a palomino horse with a golden - colored coat, which is an intermediate between chestnut and cremello.
# Answer:
An example of incomplete dominance is the inheritance of flower color in snapdragons. When a homozygous red - flowered snapdragon (RR) is crossed with a homozygous white - flowered snapdragon (rr), the heterozygous offspring (Rr) have pink flowers (an intermediate phenotype between red and white).

### Question 14: What is codominance?
# Brief Explanations:
Codominance is a type of non - Mendelian inheritance. In codominance, both alleles of a gene are fully expressed in the heterozygous condition. This means that the phenotype of the heterozygote shows the traits of both homozygous parents simultaneously, rather than an intermediate or a dominant - recessive relationship. For example, in human blood type, the AB blood type is a result of codominance. If a person has the allele for A blood type (I^A) and the allele for B blood type (I^B), both alleles are expressed, and the person has both A and B antigens on their red blood cells, resulting in AB blood type.
# Answer:
Codominance is a form of inheritance in which both alleles of a gene are fully expressed in the heterozygous individual, so the phenotype of the heterozygote shows the traits of both homozygous phenotypes simultaneously.

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Question

Explanation:

Question 12: What two characters did Gregor Mendel study when he conducted dihybrid crosses?

Step 1: Recall Mendel's dihybrid cross

Step 2: Analyze the Punnett square

Step 3: Determine the phenotypic ratio

Answer:

Question 12a: Dihybrid crosses can be used when the genes are on ______ chromosomes.