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Questions and Answers
Overdominance is also known as ______ advantage.
Overdominance is also known as ______ advantage.
heterozygote
Individuals with ______ anemia have an abnormal form of hemoglobin.
Individuals with ______ anemia have an abnormal form of hemoglobin.
sickle-cell
The alleles ______ and HbS encode for normal and abnormal hemoglobin respectively.
The alleles ______ and HbS encode for normal and abnormal hemoglobin respectively.
HbA
HbS HbS individuals experience sickling, which shortens the life span of their ______.
HbS HbS individuals experience sickling, which shortens the life span of their ______.
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In ______, both alleles in a heterozygote are expressed phenotypically.
In ______, both alleles in a heterozygote are expressed phenotypically.
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The blood type O represents a dominant/recessive relationship where if A and B genes are expressed, then O doesn’t get expressed. Examples of ______ include livestock.
The blood type O represents a dominant/recessive relationship where if A and B genes are expressed, then O doesn’t get expressed. Examples of ______ include livestock.
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During co-dominance, both the traits are expressed ______ of each other.
During co-dominance, both the traits are expressed ______ of each other.
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In sex-influenced inheritance, an allele is dominant in one sex but ______ in the other.
In sex-influenced inheritance, an allele is dominant in one sex but ______ in the other.
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Scurs in cattle are an example of a trait that is dominant in ______ and recessive in females.
Scurs in cattle are an example of a trait that is dominant in ______ and recessive in females.
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Most sex-influenced traits are ______.
Most sex-influenced traits are ______.
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In incomplete dominance, the heterozygote exhibits a phenotype that is ______ between the phenotypes of the two homozygotes.
In incomplete dominance, the heterozygote exhibits a phenotype that is ______ between the phenotypes of the two homozygotes.
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In the four-o’clock plant, the CR allele represents the wild-type allele for ______ flower color.
In the four-o’clock plant, the CR allele represents the wild-type allele for ______ flower color.
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CRCW flowers are ______ because 50% of the CR protein is not sufficient to produce the red phenotype.
CRCW flowers are ______ because 50% of the CR protein is not sufficient to produce the red phenotype.
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The F2 generation in incomplete dominance results in a ______ ratio of phenotypes.
The F2 generation in incomplete dominance results in a ______ ratio of phenotypes.
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Mendel concluded that RR and Rr genotypes produced ______ peas.
Mendel concluded that RR and Rr genotypes produced ______ peas.
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Curly hair is the ______ trait in humans, while straight hair is the recessive trait.
Curly hair is the ______ trait in humans, while straight hair is the recessive trait.
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The resulting phenotype of wavy hair in humans is an intermediate between ______ and curly hair.
The resulting phenotype of wavy hair in humans is an intermediate between ______ and curly hair.
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Offsprings formed from two parents with homozygous genotypes will have a genotypic ratio of ______.
Offsprings formed from two parents with homozygous genotypes will have a genotypic ratio of ______.
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Complementation occurs when two different parents with the same recessive phenotypes produce offspring with a ______ phenotype.
Complementation occurs when two different parents with the same recessive phenotypes produce offspring with a ______ phenotype.
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Gene modification involves an allele of one gene modifying the ______ outcome of the alleles of a different gene.
Gene modification involves an allele of one gene modifying the ______ outcome of the alleles of a different gene.
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Gene redundancy means that the loss of function in a single gene has no phenotypic effect, but the loss of function of ______ genes does have an effect.
Gene redundancy means that the loss of function in a single gene has no phenotypic effect, but the loss of function of ______ genes does have an effect.
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In a cross involving a two-gene interaction, distinct phenotypes can be produced due to ______.
In a cross involving a two-gene interaction, distinct phenotypes can be produced due to ______.
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Bateson and Punnett obtained true-breeding varieties with ______ flowers from sweet pea.
Bateson and Punnett obtained true-breeding varieties with ______ flowers from sweet pea.
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The alleles cc and pp are said to be ______ to the alleles Pp and Cc respectively.
The alleles cc and pp are said to be ______ to the alleles Pp and Cc respectively.
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Both enzymes are needed to produce ______ pigment in sweet pea flowers.
Both enzymes are needed to produce ______ pigment in sweet pea flowers.
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Epistasis refers to the relationship between alleles of ______ different genes.
Epistasis refers to the relationship between alleles of ______ different genes.
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In overdominance, the heterozygote has a trait that confers a greater level of reproductive success than either ______ has.
In overdominance, the heterozygote has a trait that confers a greater level of reproductive success than either ______ has.
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Codominance occurs when the heterozygote expresses both ______ simultaneously without forming an intermediate phenotype.
Codominance occurs when the heterozygote expresses both ______ simultaneously without forming an intermediate phenotype.
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Sex-influenced inheritance refers to the effect of sex on the ______ of the individual.
Sex-influenced inheritance refers to the effect of sex on the ______ of the individual.
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In sex-limited inheritance, a trait occurs in only one of the two ______.
In sex-limited inheritance, a trait occurs in only one of the two ______.
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A lethal allele is one that has the potential of causing the ______ of an organism.
A lethal allele is one that has the potential of causing the ______ of an organism.
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In overdominance, heterozygotes may exhibit increased resistance to ______ by microorganisms.
In overdominance, heterozygotes may exhibit increased resistance to ______ by microorganisms.
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The molecular mechanism of sex-influenced inheritance may involve regulation by ______ hormones.
The molecular mechanism of sex-influenced inheritance may involve regulation by ______ hormones.
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Lethal alleles are commonly loss-of-function alleles that encode proteins necessary for ______.
Lethal alleles are commonly loss-of-function alleles that encode proteins necessary for ______.
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Cattle scur alleles can produce a phenotype of ______ in males and females.
Cattle scur alleles can produce a phenotype of ______ in males and females.
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In sex-limited traits, characteristics may only occur in one of the two ______.
In sex-limited traits, characteristics may only occur in one of the two ______.
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A lethal allele can cause the ______ of an organism.
A lethal allele can cause the ______ of an organism.
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Lethal alleles are generally inherited in a ______ manner.
Lethal alleles are generally inherited in a ______ manner.
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Huntington disease is an example of a lethal allele that affects individuals later in ______.
Huntington disease is an example of a lethal allele that affects individuals later in ______.
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Conditional lethal alleles may kill an organism only under specific environmental ______.
Conditional lethal alleles may kill an organism only under specific environmental ______.
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Semilethal alleles impact only some individuals in a ______.
Semilethal alleles impact only some individuals in a ______.
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Pleiotropic effects refer to multiple impacts of a single gene on the ______ of an organism.
Pleiotropic effects refer to multiple impacts of a single gene on the ______ of an organism.
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Cystic fibrosis mutation affects the transport of ______ ions.
Cystic fibrosis mutation affects the transport of ______ ions.
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The ______ gene is responsible for the migration and survival of melanoblasts in coat color patterns.
The ______ gene is responsible for the migration and survival of melanoblasts in coat color patterns.
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Gene interactions influence the outcome of a single ______.
Gene interactions influence the outcome of a single ______.
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______ is an inheritance pattern where one gene's alleles mask the effects of another.
______ is an inheritance pattern where one gene's alleles mask the effects of another.
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Essential genes are genes required for ______.
Essential genes are genes required for ______.
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Sexual dimorphism can be seen in physical traits such as ______ in humans.
Sexual dimorphism can be seen in physical traits such as ______ in humans.
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Mendelian ratios can be affected when alleles are ______ in their expression.
Mendelian ratios can be affected when alleles are ______ in their expression.
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Study Notes
Incomplete Dominance
- Heterozygote exhibits an intermediate phenotype between the two homozygotes
- Example: Flower color in four o'clock plants
- Two alleles: CR (red) and CW (white)
- CRCR = red flowers
- CWCW = white flowers
- CRCW = pink flowers
- F2 generation ratio: 1:2:1 (red:pink:white), not 3:1 like in simple Mendelian inheritance
- Pea shape example shows incomplete dominance at the microscopic level regarding starch biosynthesis.
Overdominance
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Heterozygote has greater reproductive success than either homozygote
-
Also called heterozygote advantage
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Heterozygote (Aa) at one or more loci is superior to homozygotes (AA or aa)
-
Example: Sickle-cell anemia
- Autosomal recessive disorder
- Affected individuals produce abnormal hemoglobin (HbS)
- Normal hemoglobin is encoded by HbA
- HbS HbS = sickle cell anemia
- HbA HbS = malaria resistance
- HbA HbA = malaria susceptibility
-
Two major ramifications:
- Sickling of red blood cells shortens their life span, leading to anemia.
- Sickle cells clump, blocking capillary circulation.
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Phenotype falls outside the range of the parents
- If one homozygote is tall (TT) and the other is short (tt), the heterozygote (Tt) might be extra tall.
Codominance
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Both alleles in a heterozygote are expressed without forming an intermediate phenotype
- Example: Human blood type
-
Three alleles: IA, IB, i
- i is recessive to IA and IB
- ii= type O blood
- IAIA or IAi= type A blood
- IBIB or IBi= type B blood
- IAIB= type AB blood
-
IA and IB are codominant
- Both antigens are expressed simultaneously in cells
-
Examples in livestock:
- Chickens with white and black feathers
- Spotted cows
Sex-Influenced Traits
- An allele is dominant in one sex but recessive in the other
- Most are autosomal, not sex-linked
- Example: Scurs in cattle
- Dominant in males, recessive in females
Sex-Limited Traits
- Traits expressed in only one sex
- Generally autosomal
- Example:
- Ovaries in females, testes in males
- Plumage and comb size in chickens
Lethal Alleles
- Alleles that can cause the death of an organism
- Typically a result of mutations in essential genes.
- Usually inherited recessively.
- Prevent cell division early in life or later in life.
- Affects Mendelian ratios.
- Example: Manx cat
- Dominant mutation affecting the spine.
- Shortens the tail in heterozygotes.
- Lethal as a homozygote ( MM= early embroyonic death)
Conditional Lethal and Semilethal Alleles
- Kill an organism only under specific environmental conditions
- Temperature-sensitive (ts):
- Typically, a protein misfolds at higher temperatures, becoming nonfunctional.
- Example: Drosophila larvae
- Semilethal: affect some, but not all individuals in a population.
- Environmental factors may lessen their effects.
- Temperature-sensitive (ts):
Gene Interactions
- Two or more genes affect a single trait
- Morphological traits (height, weight, pigmentation) involve multiple genes and environmental factors.
Epistasis
- One gene masks the phenotypic effects of another
- Example: Flower color in sweet peas (Lathyrus odoratus)
- Two genes affecting flower color.
- Mutations in allele were in different genes.
- Both/two enzymes needed to form purple pigment (c allele masks the P allele, pp masks the C allele).
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Description
Explore the concepts of incomplete dominance and overdominance in genetics. Discover how heterozygotes can exhibit unique phenotypes and gain reproductive advantages over homozygotes through examples such as flower color in four o’clock plants and sickle-cell anemia. This quiz will test your understanding of these fundamental genetic principles.
