Genetics and Inheritance Patterns (Hard)

Questions and Answers

What is the reason behind the non-expression of a dominant allele in an individual despite its presence?

The protein encoded by the gene may not exert its effects (correct)

Genetic polymorphism

The presence of a lethal allele

Environmental influences

What is the term for the pattern of inheritance where the heterozygote has a trait that is more beneficial than either homozygote?

Incomplete dominance

Overdominance (correct)

Co-dominance

Dominance

In a cross between homozygous red-flowered and homozygous white-flowered parents, what is the expected phenotype of the heterozygous offspring?

No flowers

Red flowers

Pink flowers (correct)

White flowers

What is the term for the pattern of inheritance where both alleles are expressed simultaneously without forming an intermediate phenotype?

Co-dominance Signup and view all the answers

What is the potential benefit of being heterozygous for a particular gene?

Production of more forms of protein dimers with enhanced function Signup and view all the answers

What is the term for the phenomenon where a dominant allele is not expressed despite its presence?

Incomplete penetrance Signup and view all the answers

What is the primary goal of examining different patterns of Mendelian inheritance?

To understand the molecular expression of a gene and its effect on a trait Signup and view all the answers

What is the reason behind the beneficial effects of being heterozygous for a particular gene?

Increased resistance to infection by microorganisms Signup and view all the answers

What term is commonly applied to the inheritance of alleles that obey Mendel's laws and follow a strict dominant/recessive relationship?

Simple Mendelian inheritance Signup and view all the answers

What is a characteristic of alleles that display a dominant/recessive relationship?

50% of the protein produced by a single copy of the dominant allele is sufficient to produce the dominant trait Signup and view all the answers

What is the term for the pattern of inheritance where the heterozygote has a phenotype that is intermediate between the two homozygotes?

Incomplete dominance Signup and view all the answers

What is an example of a trait that deviates from the simple dominant/recessive relationship?

A trait with three or more alleles Signup and view all the answers

What is the effect of a lethal allele on the phenotype of an organism?

It causes the death of the organism Signup and view all the answers

What is genetic polymorphism?

The presence of multiple alleles of a single gene in a population Signup and view all the answers

What can be a result of a mutation in a gene?

A change in the protein function Signup and view all the answers

What is the relationship between the molecular expression of a gene and the trait itself?

The molecular expression of a gene determines the trait Signup and view all the answers

What is the characteristic of codominant alleles at the molecular level?

They encode proteins that function slightly differently. Signup and view all the answers

In X-linked inheritance, what is the effect of a single copy of a dominant allele in a heterozygous female?

It produces 50% of the protein, which is sufficient to produce the dominant trait. Signup and view all the answers

What is the defining feature of sex-influenced inheritance?

Alleles are recessive in one sex and dominant in the other. Signup and view all the answers

In sex-limited inheritance, what is the essential factor for producing a particular phenotype?

Sex hormones produced in only one sex. Signup and view all the answers

What is an example of a sex-limited trait?

Breast development in mammals. Signup and view all the answers

In codominance, what is the effect of the function of each protein in the heterozygote?

It affects the phenotype uniquely. Signup and view all the answers

What is the characteristic of X-linked alleles in males?

They have one copy of the allele. Signup and view all the answers

What is the difference between sex-influenced and sex-limited inheritance?

Sex-influenced inheritance affects both sexes, while sex-limited inheritance affects only one sex. Signup and view all the answers

Study Notes

Inheritance Patterns

Incomplete Penetrance: A dominant allele is present, but its effects are not seen due to environmental influences or counteracting proteins from other genes.

Incomplete Dominance

A heterozygote has a phenotype that is intermediate between the two corresponding homozygotes, e.g., a cross between red-flowered and white-flowered parents produces pink-flowered offspring.

Overdominance

A heterozygote has a trait that is more beneficial than either homozygote.
Three ways heterozygotes gain benefits:
- Increased resistance to infection by microorganisms
- Producing more forms of protein dimers with enhanced function
- Producing proteins that function under a wider range of conditions

Extensions of Mendelian Inheritance

Mendelian inheritance describes patterns that obey two laws: the Law of Segregation and the Law of Independent Assortment.
Simple Mendelian inheritance involves a single gene with two different alleles that display a simple dominant/recessive relationship.

Codominance

The codominant alleles encode proteins that function slightly differently from each other, and the function of each protein in the heterozygote affects the phenotype uniquely.
Example: blood typing, where an individual carrying the A and B alleles will have an AB blood type.

X-linked Inheritance

Inheritance of genes located on the X chromosome.
In mammals and fruit flies, males have one copy of X-linked genes, whereas females have two copies.
If a pair of X-linked alleles shows a simple dominant/recessive relationship, 50% of the protein produced by a single copy of the dominant allele in a heterozygous female is sufficient to produce the dominant trait.

Sex-influenced Inheritance

The effect of sex on the phenotype of an individual.
Some alleles are recessive in one sex and dominant in the opposite sex.
Sex hormones may regulate the molecular expression of genes, influencing the phenotypic effects of alleles.

Sex-limited Inheritance

Traits that occur in only one of the two sexes.
Example: breast development in mammals.
Sex hormones that are primarily produced in only one sex are essential to produce a particular phenotype.

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Description

Learn about incomplete penetrance, a phenomenon in genetics where a dominant allele is not expressed despite being present. Explore examples and molecular reasons behind it.