Biology Test 311

phenotype of organism not affected when it produce normal enzyme

In a monohybrid cross, Mendel observed that the phenotypic ratio in the F₂ generation was 3:1, where three individuals showed the dominant trait for every one individual that showed the recessive trait. This ratio is a fundamental principle in Mendelian genetics, illustrating how dominant and recessive traits are inherited when crossing two heterozygous parents. An interesting additional fact is that Mendel's work laid the foundation for modern genetics, yet his contributions were not recognized until after his death.

father has to be affected

In a dihybrid cross, Mendel found that the genotypic ratio in the F₂ generation is 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1. This ratio represents the distribution of genotypes for two different traits, showing how alleles for different genes assort independently during gamete formation. This discovery led to the formulation of Mendel's law of independent assortment. An additional interesting fact is that this principle only applies when the genes in question are located on different chromosomes or are far apart on the same chromosome.

Down's syndrome is not a Mendelian disorder; it is a chromosomal disorder caused by the presence of an extra copy of chromosome 21 (trisomy 21). Mendelian disorders are caused by mutations in a single gene and follow Mendel's laws of inheritance. Down's syndrome's occurrence is related to chromosomal nondisjunction rather than single-gene mutations. An interesting fact is that Down's syndrome is one of the most common chromosomal abnormalities in humans.

Product of regulator gene is important it should not present close to lac genes

When a homozygous dominant tall pea plant (TT) is crossed with a homozygous recessive dwarf pea plant (tt), all the offspring (F1 generation) will be heterozygous (Tt) and exhibit the dominant tall phenotype. This is a classic example of Mendel's law of dominance, where the dominant allele masks the presence of the recessive allele in the heterozygote. An interesting fact is that this simple cross was one of the key experiments that helped Mendel deduce the basic principles of genetics.

The term "homozygous" refers to an organism that has two identical alleles for a particular trait. This can be either homozygous dominant (TT) or homozygous recessive (tt) for that trait. This genetic makeup determines the organism's phenotype for simple Mendelian traits. An interesting fact is that homozygous individuals are true-breeding for a trait, meaning they will only produce offspring with the same phenotype for that trait when crossed with another homozygous individual.

Blood type AB in humans is an example of co-dominance, where both A and B alleles express themselves equally in the phenotype. Individuals with AB blood type have both A and B antigens on the surface of their red blood cells. This contrasts with incomplete dominance, where the heterozygote expresses a blend of the two parental phenotypes. An interesting fact is that the ABO blood group system was the first genetic polymorphism discovered in humans.

non-functional origin give zero copy number