Genetics of Sweet Pea Flower Color

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Questions and Answers

What ratio is observed in the F2 generation of the sweet pea flower color cross?

3:1

1:1:1:1

9:3:3:1

9:7 (correct)

What type of genetic interaction is described when recessive alleles at either of two loci can mask the expression of dominant alleles?

Incomplete dominance

Duplicate recessive epistasis (correct)

Codominance

Epistatic dominance

In the context of the flower color cross in sweet peas, what phenotype results from the combination of dominant alleles A and B?

White flowers

Purple flowers (correct)

Orange flowers

Pink flowers

Which phenotype represents the homozygous recessive condition in the sweet pea flower color example?

aabb Signup and view all the answers

What is the phenotypic ratio observed in the F2 generation of the awned and awnless plant cross?

15 Awned : 1 Awnless Signup and view all the answers

During the F1 interbreeding of purple and white sweet pea plants, which phenotypes appear in the resulting F2 generation?

Purple and white flowers Signup and view all the answers

What does duplicate dominant epistasis refer to in this context?

When either of two dominant alleles can mask the expression of recessive alleles. Signup and view all the answers

In the described genetic cross, what is the genotype of the offspring that do not exhibit the awn character?

aabb Signup and view all the answers

Which of the following genotypes would guarantee the development of an awn in the plants?

AABb Signup and view all the answers

Which statement correctly describes the outcome of the cross between the awned and awnless strains?

The presence of allele A alone is sufficient to develop an awn. Signup and view all the answers

What is the term used for the gene that masks the effect of another gene?

Epistatic gene Signup and view all the answers

Which type of gene action results in a phenotypic ratio of 9:3:4?

Recessive epistasis Signup and view all the answers

What phenotype results from the cross of a rose comb and single comb fowl?

Walnut comb Signup and view all the answers

What is the expected phenotypic ratio in the F2 generation from dihybrid crosses?

9:3:3:1 Signup and view all the answers

Which statement correctly describes interallelic interaction?

Interaction between different genes affecting a character Signup and view all the answers

In which type of epistasis is the phenotype expressed in the ratio of 12:3:1?

Dominant epistasis Signup and view all the answers

What is the result of mating a pea combed fowl with a single combed fowl?

A 3:1 ratio in F2 Signup and view all the answers

Which gene is associated with the walnut comb phenotype?

R gene Signup and view all the answers

What is transgressive segregation?

The emergence of extreme traits in F2 individuals beyond parental limits. Signup and view all the answers

What does expressivity refer to in genetics?

The ability of a gene to show variation in phenotype among individuals. Signup and view all the answers

How is penetrance defined?

The proportion of individuals that display a visible effect of a gene. Signup and view all the answers

In the case of polydactyly, what can be said about its penetrance?

It is incompletely penetrant, as some heterozygous individuals do not exhibit the trait. Signup and view all the answers

Which statement accurately describes atavism?

It denotes the reappearance of ancestral traits in individuals. Signup and view all the answers

What is the phenotypic ratio of awned to awnless rice in the cross between AAbb and aaBB?

15:1 Signup and view all the answers

In the context of inhibitory gene action, what color do the F1 plants exhibit when crossing IIpp with iiPP?

Green Signup and view all the answers

What can be inferred about genes with incomplete expressivity?

They may result in different phenotypes among carriers. Signup and view all the answers

What would be a phenotype with complete penetrance?

All individuals displaying the polydactylous condition. Signup and view all the answers

How many phenotypic categories are observed in the F2 generation of the green and purple plant cross?

2 Signup and view all the answers

What might be an example of incomplete penetrance?

Heterozygous individuals displaying the trait only in one hand. Signup and view all the answers

What is the phenotypic ratio seen in the F2 generation when green and purple plants are crossed under inhibitory gene action?

13:3 Signup and view all the answers

Which of the following correctly describes the relationship between the dominant gene I and the purple gene P?

I masks the expression of P Signup and view all the answers

What is the genotype of the green color in plants produced by crossing IIpp and iiPP?

IIPp Signup and view all the answers

What type of gene action is described as a dominant allele at one locus masking the expression of alleles at a second locus?

Epistatic gene interaction Signup and view all the answers

In the cross between green and purple plants, what are the genotypic combinations of the offspring?

IIPP, IIPp, iiPp, Iipp Signup and view all the answers

What ratio is observed among the offspring when white and yellow fruits are crossed?

12 White: 3 Yellow: 1 Green Signup and view all the answers

Which term describes genes that enhance or reduce the effects of a major gene?

Modifying genes Signup and view all the answers

What type of character is typically governed by one or more major genes or oligogenes?

Qualitative characters Signup and view all the answers

Which aspect of the piebald spotting in animals involves modifying factors that enhance the spotting gene?

They enhance the expression of the spotting gene Signup and view all the answers

Which of the following is considered a major gene controlling a specific trait?

ss genotype producing piebald spotting Signup and view all the answers

Which statement about quantitative characters is true?

They are influenced by multiple minor genes. Signup and view all the answers

What role do minor genes play in the expression of traits?

They modify and influence major traits. Signup and view all the answers

Which statement accurately reflects the concept of polygenes?

They are responsible for traits showing continuous variation. Signup and view all the answers

Study Notes

Types of Gene Action

Gene interaction can be intra-allelic (within the same allele) or interallelic (between different alleles).
Interallelic interaction is called epistasis.
Epistatic genes mask the effects of other genes.
Hypostatic genes have their effects masked by epistatic genes.
Epistasis modifies the expected phenotypic ratios.
Examples of epistatic gene interactions include recessive epistasis (9:3:4), dominant epistasis (12:3:1), dominant and recessive epistasis (13:3), duplicate recessive epistasis (9:7), duplicate dominant epistasis (15:1), and polymeric gene interaction (9:6:1).

Dihybrid Ratio

A classical example of gene interaction is the dihybrid ratio (9:3:3:1) in fowls, influencing comb shape.

Comb Shape in Fowls

Different breeds of poultry have different comb shapes (e.g., rose, pea, single, walnut).
Comb shape is controlled by multiple genes, showcasing gene interaction.
Crosses between different comb types show specific ratios in the F2 generation.

Duplicate Recessive Epistasis (Complimentary Gene Action)

Recessive alleles at two loci can mask the dominant alleles' expression in flower colour.
A classic example is the purple colour in sweet peas.
Lack of both dominant alleles results in white flower colour.
This scenario causes a 9:7 phenotypic ratio in the F2 generation.

Duplicate Gene Action (15:1) (Duplicate Dominant Epistasis)

A dominant allele at either of two loci can mask the expression of recessive alleles.
Awn (hairs) presence in rice is affected by two dominant alleles.
Awnless trait appears only when both alleles are recessive.
This leads to a 15:1 F2 phenotypic ratio.

Inhibitory Gene Action (13:3)

A dominant allele at one locus can mask the expression of both dominant and recessive alleles at another locus.
An example in rice plants involves green (I) and purple (P) colour expression.
In homozygous recessives, the 13:3 F2 phenotypic ratio is observed.

Supplementary Gene Action (Recessive Epistasis)

One dominant gene has a role and another affects the phenotype's expression.
For instance, in wheat with purple or red colours or white.
A specific phenotypic ratio is observed in the F2 generation (9:3:4).

Additive Factors (Polymeric Gene Action)

Two or more genes can cumulatively influence a phenotype.
Example with length of awns (hairs) in barley
The combined effect results in an additive effect on the phenotype's expression.
This often shows a 9:6:1 F2 phenotypic ratio in barley, when two genes influence awn length.

Dominant Epistasis (12:3:1)

A dominant allele at one locus can mask the expression of alleles at another locus.
Demonstrated in fruit colour, a dominant gene W masks the expression of yellow or green coloration.

Modifying Genes

Modifying genes influence the phenotypic effect of a major gene.
Their effect is cumulative or additive.
They can enhance or reduce a phenotype.
They are crucial in creating continuous variation in traits like spotting in animals.

Inheritance of Quantitative Characters (Polygenes)

Quantitative traits (e.g., height, grain yield) show continuous variation.
Multiple genes (polygenes) influence these traits.
Environmental factors also impact quantitative traits.

Transgressive Segregation

Offspring in the F2 generation can show phenotypes outside the parental range.
Due to the segregation of alleles producing positive effects,
This can result in either higher or lower intensities of the trait.

Expressivity

The degree of a gene's phenotype expression.
Can vary even when the genotype is the same
Indicates how consistently the gene affects the phenotype.

Penetrance

The proportion of individuals with a specific genotype that express the corresponding phenotype.
Can be complete, or incomplete.

Polydactyly

Polydactyly is an example of a condition with extra digits.
It's sometimes influenced by a dominant or incompletely dominant gene.

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Description

Test your knowledge on the genetic crosses of sweet pea flowers, focusing on flower color and plant characteristics. This quiz covers phenotypic ratios in F2 generations, genetic interactions, and the effects of alleles. Dive into the fascinating world of plant genetics and find out how dominant and recessive traits manifest!