Bio 103 - Chapter 14 (2) - Pharmacgy

Mendel used the scientific approach to identify two laws of inheritance. This means that he followed a systematic and evidence-based process to study and understand how traits are passed down from one generation to the next. By conducting experiments with pea plants and analyzing the patterns of inheritance, Mendel formulated the laws of segregation and independent assortment, which laid the foundation for the field of genetics. Therefore, the statement "Mendel used the scientific approach to identify two laws of inheritance" is true.

Tag-Sachs disease is indeed an inherited disorder in humans. It is a rare genetic disorder caused by a deficiency of an enzyme called hexosaminidase A (Hex A). This enzyme is responsible for breaking down a fatty substance called GM2 ganglioside in the brain and spinal cord. Without enough Hex A, GM2 ganglioside accumulates, leading to the destruction of nerve cells in the brain. This results in various symptoms such as progressive loss of motor skills, developmental regression, seizures, and eventually, premature death. Since it is inherited, individuals with Tay-Sachs disease have a faulty gene that is passed down from their parents.

Gregor Mendel drew the conclusion that traits are inherited in discrete units, and are not the result of "blending" from his experiments with pea plants. This means that traits are passed down from parents to offspring in a predictable and independent manner, rather than being a mixture or combination of the parents' traits. Mendel's experiments showed that certain traits would be expressed in the offspring, while others would not, indicating that there is a clear separation and segregation of traits. This concept of discrete inheritance units laid the foundation for our understanding of genetics.

The probability that their first child will have albinism is 1/4. Since albinism is a recessive trait, both parents must carry the recessive gene in order for their child to have albinism. In this case, both parents have one parent who has albinism, which means they each carry one copy of the recessive gene. When they have a child, there is a 1/4 chance that both parents will pass on their recessive genes, resulting in the child having albinism.

A genotype refers to the specific combination of genes present in an organism, which determines its genetic makeup and potential traits. It is a fundamental concept in genetics and is responsible for the inheritance of traits from parents to offspring. Therefore, the statement "A genotype is the genetic makeup of a trait" is correct because it accurately describes the relationship between genotype and traits.

Inheritance patterns can be more complex than predicted by simple Mendelian genetics because there are many factors that can influence the expression of genes. Mendelian genetics only considers the inheritance of single genes, but in reality, many traits are influenced by multiple genes and environmental factors. Additionally, there are different types of inheritance patterns, such as incomplete dominance, codominance, and polygenic inheritance, that do not follow the simple dominant/recessive pattern described by Mendel. Therefore, it is true that inheritance patterns can be more complex than predicted by simple Mendelian genetics.

Incomplete dominance is the type of dominance observed when the F1 offspring of a cross between two different homozygous parents display an intermediate phenotype. In this case, when a red flower mates with a white flower, the resulting F1 individuals have a pink color, which is a blend of the parental colors. This indicates that neither the red nor the white allele is dominant over the other, resulting in incomplete dominance.

Skin pigmentation is considered as a quantitative character because it can be measured and expressed numerically. Quantitative characters are traits that can be measured on a continuous scale, such as height, weight, or skin color. In the case of skin pigmentation, it can be measured using various methods, such as spectrophotometry or visual assessment, and the results can be quantified using numerical values. Therefore, skin pigmentation fits the definition of a quantitative character.

A test cross is performed to determine the genotype of an organism with a dominance phenotype. In a test cross, the organism with the dominant phenotype is crossed with a homozygous recessive individual. If all the offspring have the dominant phenotype, it suggests that the organism is homozygous dominant. However, if some of the offspring have the recessive phenotype, it indicates that the organism is heterozygous. Therefore, a test cross is a useful method to determine the genotype of an organism with a dominance phenotype.

Phenotype refers to the observable characteristics of an organism, which are determined by the interaction between its genes (genotype) and the environment. Alternative versions of genes are actually called alleles, not phenotype. Alleles are different forms of the same gene that can produce variations in the phenotype. Therefore, the given answer "False" is correct.

The ABO system has 6 genotypes and 4 phenotypes. This is because there are three alleles that determine blood type (A, B, and O), and each individual has two of these alleles. The possible genotypes are AA, AO, BB, BO, AB, and OO. However, the phenotypes are only A, B, AB, and O, as the presence or absence of the A and B antigens on red blood cells determines the blood type.

Complete dominance refers to a situation where one allele completely masks the expression of the other allele in a heterozygous individual. In Tay-Sachs disease, a recessive genetic disorder, the presence of a normal allele is sufficient to prevent the disease from occurring. Therefore, the normal allele exhibits complete dominance over the disease-causing allele, as individuals with one normal allele and one disease-causing allele are phenotypically normal.

When two individuals with the genotype AaBbCc are mated, each trait is inherited independently. The probability of an offspring being homozygous recessive for each trait is 1/4 (since it requires both recessive alleles). Since there are three traits, the probability of an offspring being homozygous recessive for all three traits is (1/4) * (1/4) * (1/4) = 1/64. Therefore, the fraction of the offspring expected to be homozygous recessive for the three traits is 1/64.

The MN phenotype is not intermediate between M and N phenotypes. Instead, it is a distinct phenotype that can be inherited from both M and N alleles. The M and N alleles are codominant, meaning that both alleles are expressed equally and independently of each other. Therefore, individuals with the MN phenotype can have both M and N antigens on their red blood cells, rather than a blend of the M and N antigens.

A testcross is a breeding experiment used to determine the genotype of an individual with a dominant phenotype. In this case, the cross between Hh and hh is an example of a testcross because hh is a homozygous recessive individual, while Hh is a heterozygous individual. By crossing Hh with hh, if any of the offspring display the recessive phenotype, it can be concluded that Hh is the genotype of the parent with the dominant phenotype.