Question

QUESTION 7

What is the purpose of gap junctions?

A. To prevent the leakage of extracellular fuid.

B. To provide cytoplasmic channels between adjacent plant cells.

C. To fasten cells together.

D. To provide cytoplasmic channels between adjacent animal cells.

QUESTION 8

During which phase of the cell cycle do homologous pairs of chromosomes line up on the metaphase plate?

A. Metaphase III

B. Metaphase I

C. Metaphase

D. Metaphase II

QUESTION 9

Which one of the following is NOT a mechanism that contributes to genetics variation?

A. Random pairing of homologous chromosomes

B. Random fertilization

C. Crossing over

D. Independent assortment of chromosomes

QUESTION 10

Generally speaking, how does a proto-oncogene become an oncogene?

A. The proto-oncogene is an inactive precursor protein that is cleaved to form the mature oncogene.

B. The proto-oncogene is phosphorylated, altering the function to that of an oncogene.

C. Proto-oncogenes can never become oncogenes. These are two completely different things.

D. The proto-oncogene is mutated, altering the function to that of an oncogene.

QUESTION 11

During which process are gametes (sperm and egg) produced?

A. Mitosis

B. Budding

C. Binary Fission

D. Meiosis

Answer 1

QUESTION 7

Answer   D. To provide cytoplasmic channels between adjacent animal cells.

Gap junctions are a specialized intercellular connection between animal cells. They connect the cytoplasm of two cells and help in exchange of ions, molecules, electrical impulses, second messengers,and small metabolites between adjacent cells. These are generally composed of proteins namely connexons and pannexins which connect across the intercellular space. They are similar to plasmodesmata connections found in plant cells.

QUESTION 8

Answer B. Metaphase I

In meiosis, diploid cell contains two copies of each chromosome called homologs or homologous chromosomes. Homologs include a set of one maternal and one paternal chromosome that pair up with each other. Homologs have the same genes in the same loci. During DNA replication, each homolog consists of two identical sister chromatids. The pairs of homologous chromosomes (bivalents) get coiled, condensed and arrange themselves on a plane equidistant from the poles called the metaphase or equatorial plate. Each set of homologs pair with each other and exchange DNA.

QUESTION 9

Answer B. Random fertilization

Random fertilization is the collection of genes within one gamete and does not generate new variation within the species.

QUESTION 10

Answer D. The proto-oncogene is mutated, altering the function to that of an oncogene.

Proto-oncogenes cause normal cells to become cancerous when mutated. Mutations in proto-oncogenes lead to formation of an oncogene which leads to cancer.

QUESTION 11

Answer D. Meiosis

Gametogenesis occurs by meiotic division where diploid gametocytes give rise to haploid gamtes. In animals, meiosis results in the formation of gametes—egg and sperm. In plants, meiosis leads to production of spores.