Genetics: Incomplete Dominance and Overdominance

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Questions and Answers

Match the following inheritance concepts with their definitions:

Co-dominance = Both traits are expressed independently in the offspring Sex-influenced inheritance = An allele is dominant in one sex but recessive in the other Sex-limited inheritance = Traits that are expressed only in one sex Dominant allele = An allele that masks the presence of another allele

Match the following examples with their types of inheritance:

Black and white chickens = Co-dominance Scurs in male cattle = Sex-influenced inheritance Carrier traits in females = Sex-linked inheritance Spotted cows = Co-dominance

Match the following traits with their descriptions:

Scurs present = Dominant in males Scurs absent = Recessive mutation for both sexes White feathers = Phenotype in co-dominance Black feathers = Phenotype in co-dominance

Match the following animal breeding outcomes with their related inheritance concepts:

Breeding black and white cows = Produces spotted calves Breeding white and black chickens = Produces both feather colors Alleles in sex-influenced traits = Behave differently in males and females Purebred breeding = Guarantees uniform trait expression Signup and view all the answers

Match the following statements with their correct inheritance terms:

Both traits shown = Co-dominance Effects depend on sex = Sex-influenced inheritance Restricted to one sex = Sex-limited inheritance Only one trait expressed = Complete dominance Signup and view all the answers

Match the blood type with its corresponding genotype:

Type A = I AI A or I Ai Type B = I B I B or I B i Type AB = I A I B Type O = ii Signup and view all the answers

Match the allele with its function:

I A = Adds N-acetyl galactosamine I B = Adds galactose i = Encodes a defective enzyme I A I B = Produces both A and B antigens Signup and view all the answers

Match the blood type with its corresponding antigen presence:

Type A = A antigen present Type B = B antigen present Type AB = Both A and B antigens present Type O = No antigens present Signup and view all the answers

Match the term with its definition:

Codominance = Both alleles are fully expressed Multiple alleles = Three or more variants of a gene Antigens = Substances that trigger an immune response Genotype = Genetic makeup of an organism Signup and view all the answers

Match the blood type inheritance pattern with its description:

I A and I B = Codominant alleles i = Recessive allele AB blood type = Results from I A and I B inheritance Type O blood = Requires ii genotype Signup and view all the answers

Match the blood type with the respective sugars on its oligosaccharides:

Type A = N-acetyl galactosamine Type B = Galactose Type AB = Both N-acetyl galactosamine and galactose Type O = No sugars added Signup and view all the answers

Match the phenotype with its blood type:

A phenotype = Type A blood B phenotype = Type B blood AB phenotype = Type AB blood O phenotype = Type O blood Signup and view all the answers

Match the allele with the resulting enzyme action:

I A = Adds terminal sugar A I B = Adds terminal sugar B i = No enzyme action I A I B = Produces both A and B proteins Signup and view all the answers

Match the following plant characteristics with their genetic outcomes:

Four o'clock plant = Pink flowers in CRCW genotype Pea shape = Round peas from RR and Rr genotypes Pea genotype (rr) = Produces wrinkled peas F2 generation = Exhibits a 1:2:1 phenotypic ratio Signup and view all the answers

Match the following hair types with their genetic description:

Curly hair = Dominant trait in humans Straight hair = Recessive trait in humans Wavy hair = Intermediate phenotype due to incomplete dominance Homozygous genotypes = Parents that produce offspring with genotypic ratio 1:2:1 Signup and view all the answers

Match the following alleles with their corresponding flower colors:

C R = Wild-type allele for red flower color C W = Allele for white flower color C R C W = Genotype for pink flowers 50% = Proportion of CR protein in pink flowers Signup and view all the answers

Match the following concepts with their corresponding examples:

Phenotype = Observable traits in organisms Heterozygote = Organism with two different alleles Homozygous = Organism with identical alleles Allele = Variant form of a gene Signup and view all the answers

Match the following genetic terms with their definitions:

Mendelian inheritance = Traditional genetic principles established by Gregor Mendel Starch biosynthesis = Genetic characteristic examined microscopically in peas 1:2:1 ratio = Expected ratio in offspring from incomplete dominance 3:1 ratio = Expected ratio in simple Mendelian inheritance Signup and view all the answers

Match the following traits with their inheritance patterns:

Hair texture = A trait exhibiting incomplete dominance Flower color in four o’clock plants = Example of incomplete dominance Color of peas = Determined by dominant and recessive alleles Wavy hair in humans = Intermediate phenotype from curly and straight hair Signup and view all the answers

Match the following genetic outcomes with their descriptions:

1:2:1 phenotypic ratio = Observed in traits exhibiting incomplete dominance Phenotypes in offspring = Result from the mixing of traits in heterozygous organisms Wild-type allele = Functioning allele contributing to dominant traits Recessive trait = Expressed only in homozygous condition Signup and view all the answers

Match the following types of alleles with their characteristics:

Essential genes = Required for survival Nonessential genes = Not required for survival but beneficial Conditional lethal alleles = Kill only under certain environmental conditions Semilethal alleles = Kill some individuals in a population Signup and view all the answers

Match the following examples with their appropriate genetic concepts:

Huntington disease = Progressive degeneration affecting older individuals Manx cat = Mutation affecting spine leading to missing offspring Cystic fibrosis = Gene affecting multiple body systems Temperature-sensitive lethals = Kill at high temperatures but survive at lower ones Signup and view all the answers

Match the following gene expressions with their effects:

Microtubule proteins = Affect cell division and movement MITF gene = Required for proper melanoblast survival CFTR gene = Regulates ionic balance in cells Gene interactions = Influence outcome of a single trait Signup and view all the answers

Match the following terms with their meanings:

Pleiotropy = A single gene affects multiple traits Epistasis = One gene masks the effect of another Sex-limited traits = Traits that occur in only one sex Phenotype = Observable characteristics of an organism Signup and view all the answers

Match the following genetic phenomena with their implications:

Scurs = ScPScP and ScPScA genotypes Irish spotting = SI allele effect on pigmentation Extreme white spotting = SW allele effect on pigmentation Lethal homozygous condition = Example seen in Manx cats Signup and view all the answers

Match the following types of phenotypes with their descriptions:

Complex phenotypes = Caused by mutations in single genes Conditional lethal alleles = Only lethal in particular environments Homozygous lethality = No offspring with MM genotype present Progressive diseases = Impact individuals later in life Signup and view all the answers

Match the following descriptions with their corresponding terms:

Essential genes = Approximately 1/3 of all genes Nonessential genes = Contribute to fitness but not survival Scurs in cattle = Controlled by specific scur alleles White spotting in dogs = Due to MITF gene expression alterations Signup and view all the answers

Match the types of Mendelian inheritance with their descriptions:

Simple Mendelian Inheritance = Follows a strict dominant/recessive relationship X-linked Inheritance = Inheritance of genes located on the X chromosome Incomplete Penetrance = Dominant phenotype not expressed due to environmental influences Incomplete Dominance = Phenotype is intermediate between either corresponding homozygote Signup and view all the answers

Match the following allele characteristics with their types:

Recessive lethal alleles = Typically associated with essential genes Dominant alleles = Exert effects in heterozygotes Semilethal characteristics = Not all individuals are affected Temperature-sensitive lethals = Survive normally at lower temperatures Signup and view all the answers

Match the following developmental effects with their outcomes:

Microphthalmia-associated transcription factor = Affects melanocyte migration Scur allele interactions = Lead to differing male and female phenotypes Pleiotropic traits = Single gene impact on diverse characteristics Evolution of ornateness = Sexual dimorphism in bird plumage Signup and view all the answers

Match the type of inheritance with its molecular aspect:

Simple Mendelian Inheritance = Dominant allele encodes a functional protein that produces the dominant trait X-linked Inheritance = Males express the only copy of X-linked genes they carry Incomplete Penetrance = Protein encoded by the gene may not exert its effects Incomplete Dominance = 50% of a functional protein is not sufficient to produce the same trait as homozygote Signup and view all the answers

Match the inheritance types with their examples:

Simple Mendelian Inheritance = Albinism in humans X-linked Inheritance = Color blindness in males Incomplete Penetrance = Polydactyly with normal fingers Incomplete Dominance = Pink flowers from red and white parents Signup and view all the answers

Match the description of an inheritance type with its key feature:

Simple Mendelian Inheritance = Tends to show complete dominance of alleles X-linked Inheritance = Affected males cannot pass the trait to their sons Incomplete Penetrance = Not all individuals expressing the genotype show the phenotype Incomplete Dominance = Resultant phenotype is a blend of both homozygote traits Signup and view all the answers

Match the genetic phenomena with the appropriate inheritance type:

Simple Mendelian Inheritance = Mendel's classic pea plant experiments X-linked Inheritance = Hemophilia affecting males predominantly Incomplete Penetrance = Presence of the Huntington's disease allele without symptoms Incomplete Dominance = Crossing two true-breeding snapdragons showing red and white flowers Signup and view all the answers

Match the term to its explanation:

Simple Mendelian Inheritance = Describes typical dominant/recessive patterns of inheritance X-linked Inheritance = Defined by inheritance patterns related to sex chromosomes Incomplete Penetrance = Describes how environmental factors can influence phenotypic expression Incomplete Dominance = When the phenotype is a blend rather than the dominant trait alone Signup and view all the answers

Match the inheritance patterns with their impact on offspring:

Simple Mendelian Inheritance = Offspring resemble parents with dominant traits expressed X-linked Inheritance = Daughters inherit one X-linked trait from each parent Incomplete Penetrance = Might result in unexpected phenotypes amongst carriers Incomplete Dominance = Creates a predictive pattern for hybrid offspring phenotypes Signup and view all the answers

Match the definitions with the correct Mendelian inheritance patterns:

Simple Mendelian Inheritance = Obeys Mendel’s laws directly with predictable outcomes X-linked Inheritance = Gene behavior influenced by sex of the individual Incomplete Penetrance = Molecular consequences not always leading to visible traits Incomplete Dominance = Intermediate phenotype resulting from heterozygosity Signup and view all the answers

Match the inheritance pattern with its description:

Overdominance = Heterozygote has a trait conferring greater reproductive success than either homozygote Codominance = Heterozygote expresses both alleles simultaneously without an intermediate phenotype Sex-influenced inheritance = Alleles are recessive in one sex and dominant in the opposite sex Sex-limited inheritance = A trait occurs exclusively in one of the two sexes Signup and view all the answers

Match the inheritance pattern with its molecular basis:

Overdominance = Increased resistance to infection via enhanced protein functions Codominance = Proteins from codominant alleles function slightly differently Sex-influenced inheritance = Sex hormones regulate gene expression affecting phenotypes Lethal alleles = Loss-of-function alleles encoding proteins necessary for survival Signup and view all the answers

Match the inheritance pattern with an example:

Overdominance = Heterozygote advantage in survival and reproduction Codominance = AB blood type in individuals with A and B alleles Sex-limited inheritance = Breast development in mammals Lethal alleles = Mutations causing organism death due to dysfunctional proteins Signup and view all the answers

Match the inheritance pattern with its unique characteristic:

Overdominance = Confers benefits through multiple mechanisms Codominance = No blending of traits occurs Sex-influenced inheritance = Expressed differently based on the sex of the organism Lethal alleles = Associated with mutations in nonessential genes leading to lethality Signup and view all the answers

Match the inheritance pattern with its reproductive impact:

Overdominance = Increases reproductive success of heterozygotes Codominance = Allows for distinct expression of both alleles Sex-influenced inheritance = Can result in different phenotypes based on sex Sex-limited inheritance = Expressed only in individuals of one sex Signup and view all the answers

Match the concept with the correct inheritance pattern:

Increased resistance = Overdominance Simultaneous expression = Codominance Phenotypic effects linked to hormones = Sex-influenced inheritance Causes organism death = Lethal alleles Signup and view all the answers

Match the inheritance pattern with the main focus of its study:

Overdominance = Advantages of heterozygosity Codominance = Expression of multiple alleles Sex-limited inheritance = Effects of sex on trait expression Lethal alleles = Consequences of deleterious alleles Signup and view all the answers

Match the type of inheritance with its potential consequences:

Overdominance = Enhanced survival under challenging conditions Codominance = Creation of unique phenotypes without blending Sex-influenced inheritance = Variability of phenotypes in response to sex Lethal alleles = Potential extinction of organisms carrying harmful mutations Signup and view all the answers

Study Notes

Incomplete Dominance

Heterozygotes exhibit an intermediate phenotype between the two homozygotes.
Example: Flower color in four o'clock plants
- Two alleles:
  - CR = red flower color
  - CW = white flower color
- CRCW genotype results in pink flowers.
F2 generation phenotypic ratio is 1:2:1 (not 3:1 like in simple Mendelian inheritance).
Pea shape example: Although Mendel concluded that round and wrinkled peas were determined by dominant/recessive alleles, microscopic examination revealed incomplete dominance of starch biosynthesis.

Overdominance

Heterozygotes have greater reproductive success than either homozygote.
Also called heterozygote advantage.
Heterozygote (Aa) is superior to either homozygote (AA or aa).
Example: Sickle-cell anemia
- Autosomal recessive disorder.
- Affected individuals produce abnormal hemoglobin.
- Two alleles:
  - HbA = normal hemoglobin
  - HbS = abnormal hemoglobin (sickle-cell hemoglobin)
- Hb^SHb^A genotype (heterozygote) offers malaria resistance, while individuals with Hb^AHb^A are susceptible to malaria.

Codominance

Both alleles of a gene in a heterozygote are expressed.
No dominant/recessive relationship.
Example: ABO blood types in humans
- Three alleles: IA, IB, i
  - i is recessive to both IA and IB
  - ii = type O blood
  - IAIA or IAi = type A blood
  - IBIB or IBi = type B blood
  - IAIB = type AB blood
Alleles IA and IB are codominant; both are expressed in IAIB genotype (type AB blood).

Sex-Influenced Traits

An allele is dominant in one sex but recessive in the other.
Not sex-linked, meaning not on X or Y chromosomes.
Autosomal.
Example: Scurs in cattle
- Dominant in males, recessive in females.

Sex-Limited Traits

Expressed in only one sex.
Autosomal.
Example: Human sexual dimorphism
- Ovaries in females, testes in males.
- Breast development in mammals.

Lethal Alleles

Alleles that cause death of an organism.
Typically result from mutations in essential genes.
Usually inherited recessively.
May prevent cell division early in development.
Example: Huntington's disease (progressive nervous system degeneration, dementia, early death; typically appears in 30s-50s).
Example: Temperature-sensitive (ts) lethals
- Kill an organism under specific environmental conditions only (e.g., high temperature).

How Lethal Alleles Affect Mendelian Ratios

Can deviate from expected Mendelian ratios.
Example: Manx cat
- Dominant mutation affecting spine.
- Shortens tail in heterozygotes (Mm).
- Lethal as a homozygote (MM).

Complex Phenotypes Caused by Mutations in Single Genes

Pleiotropy: A single gene can influence multiple traits.
Example: Cystic fibrosis
- Mutation in CFTR gene affects multiple bodily systems (lungs, skin, etc).
White spotting in dogs/mammals
- Variation in the MITF gene influences melanocyte migration/proliferation, resulting in different coat patterns.

Gene Interactions

Two or more genes affect a single trait.
Example: Flower color in sweet peas
- Epistasis: One gene's alleles mask the effect of alleles in a different gene.
  - Need both functioning enzymes for purple pigment.
  - cc prevents purple pigment regardless of P allele.

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Description

Explore the fascinating concepts of incomplete dominance and overdominance in genetics. This quiz covers how heterozygotes exhibit intermediate phenotypes and the advantages of heterozygotes in certain conditions. Test your knowledge on flower color inheritance and genetic disorders like sickle-cell anemia.