Biology 1401 Chapter 12 Patterns Of Inheritance

A diploid organism that has two identical alleles for the same trait is called homozygous for that particular trait. This means that both alleles are the same, either both dominant or both recessive. Homozygosity leads to the expression of a single trait, as both alleles are identical and will produce the same phenotype.

Blood type O is considered the universal donor because it lacks both A and B antigens on its red blood cells. This means that blood type O can be safely given to individuals with any blood type during a blood transfusion. In contrast, individuals with blood types A, B, or AB have specific antigens on their red blood cells that can cause a reaction if given to someone with a different blood type. Therefore, blood type O is the safest option for transfusions when the recipient's blood type is unknown or when there is a shortage of compatible blood types.

When the two haploid gametes contain two different alleles of a given gene, the resulting offspring is called heterozygous. Heterozygous refers to an individual that carries two different alleles for a particular gene. In this case, the offspring inherits one allele from each parent, resulting in a heterozygous genotype. This is in contrast to homozygous, where the individual carries two identical alleles, and haploid, which refers to a cell or organism with only one set of chromosomes. "Discrete" and "a fused allele" are not correct terms to describe the resulting offspring in this scenario.

An allele that is present but unexpressed is recessive. This means that it is masked or overridden by the presence of a dominant allele. In genetics, an individual inherits two alleles for each gene, one from each parent. If a dominant allele is present, it will be expressed in the phenotype, while a recessive allele will only be expressed if both alleles are recessive. Therefore, if an allele is present but unexpressed, it suggests that it is recessive and being masked by a dominant allele.

When a dominant yellow seed-bearing plant is crossed with a recessive green seed-bearing plant, the F1 generation will all be yellow because yellow is dominant over green. However, when the F1 generation plants are crossed with each other, the resulting F2 generation will show a phenotypic ratio of 3 yellow plants to 1 green plant. This is because the yellow plants can either be homozygous dominant (YY) or heterozygous (Yy), while the green plants can only be homozygous recessive (yy). As a result, 3/4 of the F2 generation will have yellow seeds and 1/4 will have green seeds.

Mendel referred to the trait that was expressed in the hybrid, F1 or first filial generation as dominant because it was the trait that appeared in the offspring when two different traits were crossed. The dominant trait masks the expression of the recessive trait in the hybrid generation.

The genotype PpTt indicates that the plant has one allele for purple flowers (P) and one allele for tall plants (T). Since the allele for purple flowers is dominant over the allele for white flowers (p), the plant will have purple flowers. Similarly, since the allele for tall plants is dominant over the allele for dwarf plants (t), the plant will be tall. Therefore, the appearance of a plant with the genotype PpTt would be purple flowers and tall.

The allelic make up of an individual refers to the combination of alleles present in their genome. This combination determines the individual's genetic characteristics and traits. Therefore, the term "genotype" accurately describes the allelic make up of an individual. The other options, such as blueprint, phenotype, and genetic pattern, do not specifically refer to the allelic make up of an individual.

Multiple alleles refers to the presence of three or more alternative forms of a single gene in a population. These alternative forms, or alleles, can result in different variations of a particular trait. Heterozygotes refers to individuals who have two different alleles for a particular gene, while homozygotes have two identical alleles. Epistatic refers to the interaction between different genes. Multiple zygotes refers to the formation of multiple fertilized eggs. Therefore, multiple alleles is the correct term to describe the presence of three or more alternative forms of a single gene.

In a heterozygous individual, where two different alleles are present for a particular gene, the dominant allele is the one that is expressed. The dominant allele masks the expression of the recessive allele, which means that the traits associated with the dominant allele will be visible in the individual. Therefore, the correct answer is "dominant."

A heterozygote for both traits means that the individual has one dominant and one recessive allele for each trait. In this case, the individual would have one allele for purple flowers (Pp) and one allele for white flowers (pp), as well as one allele for tall plants (Tt) and one allele for dwarf plants (tt). When gametes are produced, they separate and only one allele for each trait is passed on. Therefore, the possible combinations of gametes that could be produced by this heterozygote are PT, Pt, pT, and pt.

Pleiotropy refers to the phenomenon where a single allele can have multiple effects on the phenotype. This means that the allele can influence multiple traits or characteristics in an organism. In contrast, epistasis refers to the interaction between different genes, recessive and dominant refer to the expression of alleles in relation to each other, and homozygotic refers to having two identical alleles for a particular gene. Therefore, the best explanation for the correct answer is that if an individual allele has more than one effect on the phenotype, it is said to be pleiotropic.

Dihybrid refers to an individual that possesses two different alleles for two different traits. This means that the individual has one allele for each trait from each parent, resulting in a combination of two different alleles. This is different from a monohybrid, which refers to an individual that possesses two alleles for only one trait. A homozygote refers to an individual that possesses two identical alleles for a particular trait. True breed refers to a population of individuals that consistently produce offspring with the same traits. Diallelic refers to a system with two different alleles.

A Punnett square is a tool used in genetics to determine the possible combinations of alleles and predict the ratios of genotypes and phenotypes in offspring. It helps in understanding the inheritance patterns of traits. However, it is not used to establish a pedigree, which is a diagram that shows the presence or absence of a particular trait across generations in a family. Pedigrees are used to study the inheritance of genetic disorders and determine the mode of inheritance. Therefore, establishing a pedigree is not a function of a Punnett square.

Mendel's experiments had all of the following characteristics except that he always used only two plants for his work. Mendel actually used a large number of plants in his experiments, not just two. He performed his experiments by cross-pollinating different pea plants and then observing the traits of the offspring. He studied multiple generations of plants, self-pollinating them to ensure the traits were stable. This allowed him to establish the principles of inheritance and develop his laws of genetics.

In a dihybrid cross, there are four possible gamete combinations for each trait. Since we are looking for the phenotype white, tall, we need to find the combinations that have both p and T alleles. Out of the 16 possible combinations, there are three that satisfy this condition: PT, pT, and Pt. Therefore, the answer is 3.

In carnations, the inheritance of the red pigment is not completely dominant or recessive. Instead, when a carnation plant has one copy of the red pigment gene (R) and one copy of the no pigment gene (r), it produces a smaller amount of red pigment, resulting in a pink appearance. This is an example of incomplete dominance, where neither allele is fully dominant over the other, and a blending of traits occurs.

A gene for a particular trait that is only expressed in the presence of another gene of the same kind is called a recessive gene. This means that the trait will only be visible or expressed if an individual has two copies of the recessive gene. In the presence of a dominant gene, the trait will not be expressed. This is because the dominant gene will override the expression of the recessive gene.

Mendel chose the garden pea for his work on inheritance because it had a large number of true breeding varieties already available, the generation time was short allowing for easy growth of many offspring, and he had the option to self- or cross-pollinate. However, the reason he did not choose the garden pea was because earlier investigators had shown segregation among the offspring.

The ABO blood group expression is an example of multiple alleles because there are three different alleles (A, B, and O) that determine the blood type. Each individual can inherit two alleles, resulting in four possible blood types (A, B, AB, and O). The presence of multiple alleles allows for a range of phenotypic variations in the population.

By crossing yellow-seeded plants with true breeding green-seeded plants, we can determine if the yellow-seeded plants are homozygous or heterozygous. If the offspring from this cross produce only yellow seeds, then the yellow-seeded plants are homozygous. However, if the offspring produce both yellow and green seeds, then the yellow-seeded plants are heterozygous. This is because true breeding green-seeded plants will only contribute the recessive green allele, allowing us to observe the presence or absence of the dominant yellow allele in the offspring.

Mendel's first law, also known as the law of segregation, states that alternative alleles segregate in gametes and each allele has an equal probability of being passed on into the gamete. This means that during the formation of gametes, the two alleles for a trait separate from each other so that each gamete receives only one allele. This law does not encompass the idea that all genes found in an individual are not separable into gametes. This statement contradicts Mendel's first law, as it suggests that all genes are inherited together and cannot be separated during gamete formation.

Mendel's observations that different pairs of genes assort independently of each other is known as the Statement of Assortment Principle. This principle states that the inheritance of one trait does not affect the inheritance of another trait, and they are passed down independently. Mendel's experiments with pea plants showed that the inheritance of traits such as seed color and seed shape were not linked and could be inherited separately. This principle laid the foundation for understanding the inheritance patterns of genes and formed the basis of Mendel's First Law of Heredity.

A test cross is the mating of a hybrid F1 plant with a homozygous recessive plant for the same trait. This cross is used to determine the genotype of the hybrid plant by observing the phenotypic ratios of the offspring. By crossing the hybrid with a homozygous recessive plant, if any offspring display the recessive trait, it indicates that the hybrid plant is heterozygous for the trait. This cross is commonly used in genetics to determine the genotype of an individual or to determine if an individual is homozygous or heterozygous for a specific trait.

The fact that the trait is present in every generation suggests that it is dominant. In dominant inheritance, a trait is expressed even if only one copy of the gene is present. This means that if an individual inherits the dominant allele from either parent, they will display the trait. In contrast, recessive traits require two copies of the gene to be present for the trait to be expressed. Since the question states that the trait is present in every generation, it indicates that only one copy of the gene is needed, pointing towards dominant inheritance.

Mendel's understanding of the inheritance of traits in peas, expressed in modern language, included the following concepts: parents transmit information encoded in genes, each individual contains two genes for each trait, not all genes are identical; alternative forms (alleles) exist, and each of the alleles present in an individual is discrete. However, Mendel's understanding did not include the concept that if a given allele is present, its effects will be seen in the individual. This means that the presence of an allele does not necessarily guarantee that its effects will be expressed in the phenotype of the individual.

Mendel's observation that he never got any pea plants with light purple flowers when crossing dark purple-flowered pea plants with white-flowered pea plants contradicts the idea of acquired characteristic inheritance, which suggests that traits acquired during an organism's lifetime can be passed on to the next generation. It also goes against the theory of blending inheritance, which proposes that parental traits blend together in the offspring. The assumption of direct transmission of traits would imply that the offspring should have had a mix of the parents' traits. However, Mendel's results align with the law of dominance, which states that one allele (in this case, the allele for dark purple flowers) can mask the expression of another allele (the allele for light purple flowers) in a heterozygous individual. This explains why only the dominant trait (dark purple flowers) was observed in the offspring. The laws of probability are not directly related to this specific observation.

Genes assort independently of one another because they are located on different chromosomes. Chromosomes are the structures that contain genes, and during the process of meiosis, chromosomes segregate randomly into gametes. This means that the genes on different chromosomes can be inherited independently of each other, leading to the assortment of traits that may or may not be related.

The best explanation for the differences described is that many genes, rather than one gene, control some variations in species. This means that height and eye color in humans are influenced by multiple genes, leading to a wide range of possibilities and continuous variation. In contrast, in pea plants, the tall allele is dominant over the short allele, resulting in only two distinct heights and no intermediate heights.

Plants with a genotype of PPTt can form gametes with different combinations of alleles. The genotype PPTt indicates that there are two different alleles for each gene: P and T. Since each gene can independently assort during gamete formation, there are 2^4 = 16 possible combinations of alleles that can be formed. Therefore, the correct answer is 16.

The correct genotypic ratio for yellow, round F2 individuals is 1/16 YYRR, 2/16 YYRr, 2/16 YyRR, 4/16 YyRr. This ratio is obtained by combining the genotypes of the parent peas (YYRR and yyrr) and following Mendelian inheritance patterns. The capital letters represent dominant alleles (Y and R) for yellow and round traits, while the lowercase letters represent recessive alleles (y and r) for green and wrinkled traits. The ratio reflects the different combinations of alleles that can be inherited from the parents, resulting in a variety of genotypes in the F2 generation.

Epistasis is the correct answer because it refers to the interaction between different gene pairs where one gene pair controls the expression of another gene pair. This interaction can result in the masking or altering of the phenotypic expression of the second gene pair. Epistasis is a form of genetic interaction that can have significant effects on the inheritance patterns and phenotypic variation within a population.

The observable outward manifestation of the genes of an individual is referred to as its genotype. Genotype refers to the specific genetic makeup of an individual, including all the genes they possess. It is responsible for determining the traits and characteristics that an individual may exhibit. The phenotype, on the other hand, refers to the physical expression of those genes, such as the individual's appearance, behavior, and other observable traits. Therefore, while the phenotype is the outward manifestation, the genotype is the underlying genetic blueprint that influences it.

Mendel obtained a phenotypic ratio of 3:1 (purple-flowered pea plants to white-flowered pea plants) when crossing two purple-flowered pea plants. This suggests that the trait for flower color is controlled by a single gene with two alleles, one for purple (dominant) and one for white (recessive). The heterozygous purple pea plant would have one allele for purple and one allele for white, while the homozygous recessive white pea plant would have two alleles for white. When these two plants are crossed, there is a 25% chance of obtaining a homozygous recessive white pea plant, which matches the observed phenotypic ratio.