Practice Quiz On Genetics

When pink-flowered plants were crossed and produced offspring with red, pink, and white flowers in a ratio of 1:2:1, it indicates incomplete dominance. Incomplete dominance occurs when the traits of the parents blend together in the offspring, resulting in an intermediate phenotype. In this case, the pink-flowered plants are not completely dominant over the red and white flowers, as both colors are expressed in the offspring. Therefore, the statement "This is an example of incomplete dominance" is true.

This statement is true because co-dominance occurs when both alleles for a gene are expressed equally in the phenotype of a heterozygous individual. In this case, the yellow and brown alleles are both expressed in the mixed color puppies, indicating co-dominance.

Phenotype refers to the actual physical appearance of an individual. It is the result of the interaction between an individual's genetic makeup and environmental factors. This includes observable traits such as hair color, eye color, height, and behavior. The phenotype can be influenced by both dominant and recessive alleles, as well as other genetic and non-genetic factors.

An individual who has two of the same allele is said to be homozygous. This means that both copies of the gene at a specific location on the chromosomes are identical. In other words, the individual inherited the same version of the gene from both parents. This can result in the expression of a specific trait or characteristic.

When two individuals that are heterozygous (Bb) are crossed, they can produce three possible genotypes in their offspring: BB, Bb, and bb. This is because each parent can pass on either a dominant allele (B) or a recessive allele (b), resulting in a combination of both alleles (Bb) or two copies of either allele (BB or bb) in the offspring.

Incomplete dominance is a genetic phenomenon where neither of the two alleles is completely dominant over the other, resulting in a phenotype that is an intermediate blend of the phenotypes of the two homozygotes. In other words, the heterozygote has a phenotype that is different from both the homozygotes. This is in contrast to complete dominance, where one allele is completely dominant over the other. Therefore, the statement that incomplete dominance occurs when the phenotype of the heterozygote differs from the phenotypes of both homozygotes is true.

Y-linked traits are inherited only by males because the Y chromosome is passed down from father to son. Females do not have a Y chromosome, so they cannot inherit traits that are specifically linked to it. Y-linked traits are typically rare and include characteristics such as male pattern baldness and certain types of color blindness. Since only males possess a Y chromosome, they are the only ones who can pass down Y-linked traits to their male offspring.

When an individual is homozygous for a trait, it means they have two identical alleles for that trait. In this case, the individual homozygous for black hair (BB) has two black hair alleles. On the other hand, a heterozygous individual (Bb) has one black hair allele and one allele for a different hair color, which is not specified. When these two individuals cross, their possible genotypes are BB (homozygous black hair) and Bb (heterozygous black hair).

The appearance resulting from a given gene combination is referred to as the phenotype. The phenotype includes all observable traits and characteristics of an organism, such as its physical appearance, behavior, and physiological features. It is determined by the interaction between an organism's genotype (the genetic makeup) and its environment. The phenotype is what we can see and study, making it an important factor in understanding genetics and studying the effects of genes on an organism.

An allele refers to one of several possible forms of a gene. Genes can have different variations or alleles, which can result in different traits or characteristics. Alleles can be dominant or recessive, and they determine the expression of a particular gene in an individual. Therefore, an allele is not another word for a gene, a homozygous genotype, or a heterozygous genotype, but rather a specific form or variant of a gene.

Sex-linked genetically inherited traits can appear in both males and females because they are determined by genes located on the sex chromosomes. In humans, these traits are often associated with the X chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. If a gene on the X chromosome carries a trait, it can be expressed in both males and females, although the inheritance pattern may differ. Males are more likely to express sex-linked traits because they only have one X chromosome, while females need to inherit the trait on both X chromosomes to express it.

The correct answer is "the percentage or fraction of all alleles for a specific gene represented by one specific allele." This is because allele frequency refers to the proportion of a specific allele in a population's gene pool. It is calculated by dividing the number of copies of a specific allele by the total number of alleles for that gene in the population. This measure helps in understanding the genetic diversity and evolution of a population.

A highly variable gene variant or DNA sequence present in more than 1% of a population is called a polymorphism. This means that the gene variant or DNA sequence can occur in different forms or variations within the population. These variations can be inherited and contribute to the genetic diversity within a population.

The dominance relationship between the A and B alleles of the ABO blood group gene is an example of co-dominance. This means that both alleles are expressed equally in the phenotype. In individuals with both A and B alleles, both A and B antigens are present on the surface of red blood cells, resulting in the AB blood type. This is different from complete dominance, where one allele completely masks the expression of the other, and from incomplete dominance, where a heterozygote exhibits an intermediate phenotype. Epistasis refers to the interaction between different genes, not alleles of the same gene.

The probability that the alien couple will have a child that is heterozygous for eye color is 1/2. This is because the homozygous Martian (RR) can only pass on the dominant red eye color allele (R), while the heterozygous Martian (Rr) can pass on either the dominant red allele (R) or the recessive purple allele (r). Therefore, there is a 50% chance that the child will receive the recessive purple allele from the heterozygous parent, resulting in a heterozygous genotype (Rr) for eye color.

Since both the woman and her husband show the normal phenotype for skin pigmentation, it means that they both have one dominant allele for pigmentation. However, since both of them had one parent who was an albino, it means that they both carry one recessive allele for albinism. Therefore, the probability of their first child having albinism is 25% because there is a 25% chance that both parents will pass on their recessive alleles for albinism to their child.

Males have only one X chromosome, while females have two X chromosomes. Sex-linked traits are carried on the X chromosome. Since males have only one X chromosome, they have a higher chance of expressing sex-linked traits compared to females. This is because if a male inherits a recessive allele for a sex-linked trait on his X chromosome, he does not have a second X chromosome to mask the expression of that allele. In contrast, females have two X chromosomes, so even if they inherit a recessive allele for a sex-linked trait on one X chromosome, the presence of a dominant allele on their other X chromosome can mask the expression of the recessive allele.

The chances that the alien couple will have a child with red eyes is 1. This is because the homozygous Martian (RR) will always pass on the dominant red eye allele to their offspring, while the heterozygous Martian (Rr) has a 50% chance of passing on the red eye allele. Therefore, regardless of which allele the heterozygous Martian passes on, the child will always have at least one red eye allele and will have red eyes.

The probability of the Martians having a child with purple eyes is 0. This is because the homozygous Martian (RR) does not carry the recessive gene for purple eyes, and the heterozygous Martian (Rr) only has a 50% chance of passing on the recessive gene. Therefore, there is no possibility for the child to inherit the recessive gene for purple eyes.

Since both the woman and her husband have the normal phenotype for skin pigmentation, it means that they both have one normal allele and one albino allele for the gene responsible for pigmentation. When they have children, each parent has a 50% chance of passing on either the normal allele or the albino allele. Therefore, the chance of passing on the albino allele to each child is 50%. Since the inheritance of alleles is independent in each child, the chance of their third child having albinism is also 50%. Therefore, the correct answer is 50%.

The genes in a population comprise its gene pool. The gene pool refers to the total collection of genes, including all the different alleles, present in a population. It represents the genetic diversity within a population and provides the raw material for evolution to occur. Gene flow, on the other hand, refers to the transfer of genes from one population to another. Genotype refers to the specific combination of alleles an individual possesses. Gene allocation is not a term commonly used in genetics.

The given answer is 5/24 or about 21%. This can be determined by counting the number of dominant alleles (A) in the given sequence of alleles. There are a total of 24 alleles in the sequence, and only 5 of them are dominant (A). Therefore, the frequency of the dominant allele is 5/24, which can be simplified to about 21%.

The term "dominant" refers to the ability of one allele to mask or override the expression of another allele in a hybrid individual. This means that even if an individual carries both dominant and recessive alleles for a particular trait, only the dominant allele will be expressed, while the recessive allele remains hidden or masked. Therefore, the correct answer is "one allele can mask the expression of another hybrid."

Polygenic inheritance is an exception to Mendel's principles because it involves the inheritance of traits that are controlled by multiple genes, rather than a single gene. Mendel's principles primarily focus on the inheritance of traits controlled by a single gene, and do not account for the complexity of traits controlled by multiple genes. Polygenic inheritance is observed in traits such as height, skin color, and intelligence, which are influenced by the combined effects of multiple genes.

In the given population of mice, the frequency of the 'a' allele is represented by the sequence "aaAaaaAaAaaaaaaaaaAaaaAa". To determine the frequency of the 'a' allele, we count the number of times the 'a' allele appears in the sequence. In this case, there are 19 'a' alleles out of a total of 24 alleles. Therefore, the frequency of the 'a' allele is 19/24 or approximately 79.16%.

In a heterozygote, both alleles are expressed equally and contribute to the phenotype. This is known as co-dominance. In completely dominant inheritance, one allele is dominant over the other and masks its expression. In incompletely dominant inheritance, a blending of the two alleles occurs resulting in an intermediate phenotype. Epistatic refers to the interaction between different genes where one gene masks or modifies the expression of another gene.

In a population in Hardy-Weinberg equilibrium, the frequency of a recessive allele will remain the same over time. This is because Hardy-Weinberg equilibrium assumes that there are no forces at work to change the allele frequencies in a population. The equilibrium is maintained through a balance of genetic drift, mutation, migration, and natural selection. As long as these forces are not acting upon the population, the frequency of the recessive allele will remain constant from generation to generation.

The Hardy-Weinberg equilibrium assumes that mating occurs randomly, meaning that individuals in a population have an equal chance of mating with any other individual. This assumption allows for the calculation of allele frequencies in a population. However, the given answer states that mating occurs preferentially, which contradicts the assumption of random mating. Therefore, this is not an assumption of the Hardy-Weinberg equilibrium.

Huntington's disease is a genetic disorder caused by a dominant allele. It is characterized by the progressive degeneration of nerve cells in the brain, leading to various physical and mental symptoms. The presence of a single mutated gene is enough to cause the disease, making it dominant. This means that if one parent has the disease, there is a 50% chance that their child will inherit the disorder.

When plants with red flowers are crossed with plants with white flowers, the resulting offspring will all have pink flowers. This is because the red flower parent is homozygous for the red flower trait (RR) and the white flower parent is homozygous for the white flower trait (WW). The offspring, being heterozygous (RW), will inherit one allele for red flowers and one allele for white flowers, resulting in pink flowers. Therefore, the proportion of offspring with pink flowers is 100%.

Incomplete dominance occurs when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes. In this case, individuals homozygous for the allele causing familial hypercholesterolemia completely lack receptors, while individuals homozygous for the normal allele have normal receptors. Heterozygotes, however, have only half the number of receptors, resulting in an intermediate phenotype. This demonstrates incomplete dominance, as the heterozygous phenotype is not completely dominant over the homozygous phenotypes.

Gene flow refers to the movement of genes from one population to another through migration. It occurs when individuals or their gametes migrate and breed with individuals from another population, resulting in the transfer of genetic material. This process can introduce new genetic variations into a population and increase genetic diversity. Therefore, migration is the correct answer to the question as it accurately describes gene flow.

The correct answer is "no, mating is non-random". This is because individuals with a streak of white fur between the eyes mate only with individuals lacking this marking, indicating that mating is based on a specific trait rather than random chance. This non-random mating pattern disrupts the equilibrium of the population, as it leads to the preferential selection of certain traits and can result in changes in the frequency of those traits over time.