Mr. Ducre' S Freshmen Biology Quiz #1, 2nd Quarter 2013/2014:

Genes located on homologous chromosomes can have different forms, known as alleles, which control different variations of a trait. Alleles are alternate versions of a gene that can result in different phenotypes or observable characteristics. They are responsible for the genetic diversity within a population and are passed on to offspring through gametes during reproduction.

An allele is an alternate form of a gene. Genes exist in different versions called alleles, which can have different variations or mutations. These variations in alleles contribute to the diversity of traits observed in individuals within a population.

The ratio of 9:3:3:1 in di-hybrid crosses indicates independent assortment. This means that during the formation of gametes, the alleles for two different traits segregate independently of each other. In other words, the inheritance of one trait does not influence the inheritance of the other trait. This is a key principle of Mendelian genetics and is observed when the genes for the two traits are located on different chromosomes or are far apart on the same chromosome.

The tall pea plant provides information about the phenotype because it describes a physical characteristic (tallness) of the plant. The term "phenotype" refers to the observable traits or characteristics of an organism, while "genotype" refers to the genetic makeup of an organism. In this case, the information given does not provide any details about the specific genes or alleles responsible for the tallness of the pea plant, hence it only gives information about the phenotype.

Crossing over refers to the exchange of genetic material between homologous chromosomes during meiosis. This process leads to genetic recombination, where the alleles on the chromosomes are rearranged, resulting in new combinations of genes. Therefore, the correct answer is genetic recombination.

Pollination is the process of transferring pollen grains from the male reproductive organ (stamen) to the female reproductive organ (pistil) of a flower. This transfer allows for the fertilization of the ovule, leading to the formation of seeds. Therefore, the answer "the transfer of the male pollen grain to the female organ" accurately describes the process of pollination.

When a man who is heterozygous for blood type A (genotype AO) marries a woman who is heterozygous for blood type B (genotype BO), their possible genotypes for their child are AO, BO, AB, and OO. The genotype OO represents blood type O. Therefore, there is a 25% chance that their first child will have type O blood.

Red-green color blindness is caused by a recessive allele. This means that a person needs to inherit two copies of the recessive allele (one from each parent) in order to have red-green color blindness. If a person only inherits one copy of the recessive allele, they will be a carrier of the trait but will not exhibit color blindness. This trait is more common in males because they only have one X chromosome, so if they inherit the recessive allele on their X chromosome, they will have red-green color blindness. Females, on the other hand, have two X chromosomes, so they need to inherit two copies of the recessive allele to have the trait.

The white mouse producing only brown offspring when mated with a brown mouse suggests that the white mouse carries a dominant allele for the brown fur color. Since the parents of the white mouse are both white, it is unlikely to be homozygous dominant (both alleles for brown fur color) as it would produce brown offspring when mated with another white mouse. Therefore, the white mouse is most probably heterozygous, carrying one allele for white fur color and one allele for brown fur color.

In a F1 dihybrid cross, the parents are heterozygous for both traits, so the possible genotypes of the offspring are WWGg, WWgg, wwGg, and wwgg. The probability of obtaining an individual that is wrinkled, green, and true breeding (wwgg) is 1/16 because there is only one possible genotype out of the total 16 possible genotypes.

When two blue Andalusian offspring are mated, the result will be a 100% blue phenotypic ratio in their offspring. This is because the blue color is a dominant trait in this case, and both parents contribute the blue allele to their offspring. Therefore, all the offspring will inherit the blue allele and display the blue phenotype.

The given answer, TtHH, is an example of a genotype because it represents the combination of alleles for two different traits. The letters T and H represent the dominant alleles for two different genes, while the lowercase letters t and h represent the recessive alleles. This combination of alleles determines the specific genetic makeup of an organism, in this case, for the traits represented by the genes T and H.

Cystic Fibrosis and Tay-Sachs disease are both recessive disorders that are more commonly found within specific ethnic groups. This means that individuals within these ethnic groups are more likely to carry the gene for these disorders, resulting in a higher occurrence of the diseases within these populations. This is due to the genetic inheritance patterns within these specific ethnic groups, where the gene for the disorder is more prevalent.

A Punnett Square is a grid used to predict the possible genotypes of offspring in a genetic cross. In this case, the cross is between Ww and ww. Since each parent has only one allele (W or w), the Punnett Square will have two rows and two columns, resulting in a 2x2 grid. The vertical axis represents the possible alleles from one parent (W or w), and the horizontal axis represents the alleles from the other parent (w). The intersecting cells in the grid show the possible genotypes of the offspring.

Incomplete dominance is the type of inheritance shown when a red-flowering plant is crossed with a white flowering plant and only pink-flowering plants are produced. In this type of inheritance, neither allele is completely dominant over the other, resulting in a blending of traits. In the case of flower color, the red allele and the white allele mix together to produce the pink color in the offspring.

The law of independent assortment states that the inheritance of alleles for one trait is not affected by the inheritance of alleles for a different trait if the genes for the traits are on separate chromosomes. This means that during the formation of gametes, the alleles for different traits segregate independently of each other. In other words, the inheritance of one trait does not influence the inheritance of another trait if they are located on different chromosomes. This allows for a greater variety of genetic combinations and contributes to genetic diversity.

In a monohybrid cross, two individuals with different genotypes for a single trait are crossed. This results in three different genotypes in the offspring. In a dihybrid cross, two individuals with different genotypes for two different traits are crossed. Each trait is inherited independently, so the number of possible genotypes for each trait is multiplied. Since there are two traits, there would be 2 x 2 = 4 different genotypes resulting from a dihybrid cross.

In this cross, the round hybrid pea (Ww) is crossed with a true breeding round parent (WW). Since the true breeding parent is homozygous dominant (WW), it can only contribute dominant alleles to the offspring. Therefore, all the offspring will inherit a dominant allele for round shape from the true breeding parent. As a result, all the offspring will be round.

Eye color in humans is the result of polygenic inheritance. This means that multiple genes, each with different alleles, contribute to the variation in eye color. The expression of these genes is influenced by a combination of factors, including genetic and environmental factors. Therefore, eye color cannot be determined by a single gene or a simple dominant trait, but rather by the interaction of multiple genes.

The probability of getting heads on a single flip of a fair coin is 1/2. Since there are 4 flips in total and we want heads to occur on three flips, we can calculate the probability by multiplying the probability of getting heads (1/2) three times and the probability of getting tails (1/2) once. Therefore, the probability is (1/2) * (1/2) * (1/2) * (1/2) = 1/16. However, since we are only interested in the specific scenario where heads occurs on three flips and tails on one, we need to account for the different ways this can happen. There are 4 possible arrangements of heads and tails: HHTT, HTHT, HTHH, and THHH. So, the probability is 4 * (1/16) = 1/4.