Biology: CUET Mock Test - 3 - Class 12 MCQ

Coitus or copulation is the process that leads to the release of semen from the penis into the vagina. The sperms populate the vagina along with other contents of semen. This process is called insemination.

The heart is the first organ to form in the developing fetus. It is formed after one month of pregnancy. The brain takes more time to develop.

The F2 generation in a dihybrid cross produces all possible phenotypes. The ratio obtained for it is 9:3:3:1.

Syngamy is the process of fertilization that produces a diploid cell on the fusion of two haploid cells. It is also often called internal fertilization since the process takes place on the inside. However, there are few species of organisms where syngamy occurs outside their bodies, in an external medium. Example, algae, fishes, amphibians, etc. This is also called as external fertilization.

Sperms are released into the vagina. From here, they travel through the cervix and uterus before reaching oviduct or fallopian tube, where they can encounter an egg.

Limbs and digits, along with external genitalia, are formed during the first trimester. This is a period of 12 weeks after pregnancy.

The F2 progeny of a dihybrid Mendelian cross has a phenotypic ratio of 9:3:3:1. Thus of the 1600 plants sampled, 900 will be round yellow, 300 round green, 300 wrinkled yellow and 100 wrinkled green.

The pair of chromosomes that line up during meiosis has two copies of each homologous chromosome. Hence it is called a bivalent.

Androecium is a collection of stamens. Stamens consists of anthers and filaments. Anthers are fused to the top of the filament that acts like a stalk. Pollen sacs are present on the anthers, within which are the pollen grains.

Trimesters are periods of three months’ post-pregnancy. Fetal movements can be observed starting five months’ post-pregnancy i.e., during the second trimester.

The first two laws of Mendel were based on his studies on monohybrid crosses. These were the law of dominance and the law of segregation. The dihybrid cross studies supported them, but also led to the formulation of a third law: the law of independent assortment.

Sutton and Boveri had studied the segregation of chromosomes very closely by staining the cells and then developing a differential staining approach to visualize the pairs of chromosomes. To their surprise, this was very similar to the expectation of Mendel’s factors. Hence they made the conclusion that independent separation of chromosomes should lead to independent segregation of factors.

The egg is released and awaits in ampulla for the sperm. The sperms cross the reproductive tract barriers before reaching the ampulla to fertilize the egg.

The maternal increase in the hormones is responsible for the development and growth of the fetus, maintenance of pregnancy, and the changes in metabolism in mother essential for the proper nourishment of fetus. Lactation is not a part of pregnancy. It occurs after the baby has been delivered.

The Law of Independent Assortment states the independent segregation of traits that are unrelated. Mendel drew this conclusion based on his studies on garden pea plants.

Sutton and Boveri were the key players in the world of biology during the decade of 1900-1910. They observed chromosome movements and studied Mendel’s experiments. Based on these, they devised the chromosomal theory of inheritance.

Fertilization occurs only when the egg and sperm are present in the ampulla at the same time. Hence the coitus should happen near the period of ovulation. Ovulation occurs at the end of the follicular phase or the onset of luteal phase.

The process of implantation is followed by the rapid differentiation of the inner mass of cells of the blastocyst. These cells differentiate into the outer layer of ectoderm and the inner layer of endoderm. Mesoderm arises later.

The law of independent assortment was the third law of Mendel. It states that when multiple traits are under consideration, each trait segregates independently of the other.

Sutton and Boveri were inspired by Mendel’s studies. With the advent of microscopy, they could observe the chromosomal movements during meiosis. Both of these led them to devise the chromosomal theory of inheritance.

Ovulation is the release of egg from the ovary. Spermiation is the release of sperm from testis. Insemination is the release of semen into vagina. Fertilization is the process that leads to fusion of male and female gametes.

Ectoderm and endoderm are the first layers that arise as a result of the differentiation of the implanted blastocyst. Eventually, a third layer separating ectoderm from the endoderm arises. This layer is called mesoderm.

For a dihybrid cross involving two traits, the independent law of assortment states that the traits would segregate independently of each other. Thus, the phenotypic ratio would be xy.

The chromosomal theory of inheritance was stated by Sutton and Boveri. It talks about the movement of chromosomal pairs independent of each other to reach the metaphase plate during Meiosis I.

The sperm contacts the egg cell at zona pellucida. The zona pellucida then undergoes chemical changes which renders egg insusceptible to further encounters with another sperm. This is essential to ensure that only a single sperm fertilizes the egg.

Development is the process that leads to the formation of an organism from the zygote. Potency is the ability of a cell to differentiate into another cell type. Stemness is the potential of a cell to divide indefinitely and also differentiate to multiple different cell types.

The whole image is a stamen. The blue part depicts the anther that carries the male gametes and the red part is the filament. The anther is fused with the filament.

The chromosomal theory of inheritance was devised by the observations of the movements of chromosomes during the process of meiosis. According to this theory and the experiments that validate it, the chromosomes segregate independently of each other.

The secondary oocyte released from the ovary has finished first round of meiosis. The second round of meiosis occurs in ampulla after the egg encounters the sperm. This leads to formation of large ovum and a tiny second polar body.

The stem cells are a population of cells within the inner cell mass that possess the ability to give rise to an entire organism. They have a property called stemness, which gives them this ability.