Βιολογία Διαγωνισμός 2025

Most molecular biologists believe that viruses originated from fragments of cellular nucleic acids. Which of the following observations supports this theory?

• Viruses contain either DNA or RNA.

• Viruses can only replicate inside host cells.

• Viruses can infect both prokaryotic and eukaryotic cells.

• The genomes of viruses are usually similar to the genomes of host cells.

Assuming that the replication rate at a fork is 60,000 nucleotides/min for the continuous strand and 50,000/min for the discontinuous strand. In a bacterial DNA of 300,000 base pairs, replication will be completed:

• in 5 min

• in 6 min

• in 3 min

• in 5 min for half the molecule and in 6 min for the other half

The cultivated wheat can be octoploid (8n=88) and originates from the normal diploid wild-type plant. In a wild-type plant, how many DNA molecules are included in the total cells resulting from the reduction I of an immature germ cell?

• 11

• 22

• 44

• 88

The diagram shows the change in the rate of the enzymatic reaction of lactase as a function of the increase in the substrate of lactose. The rate of the reaction remains constant from point X onwards because:

• the active site of all enzymes is occupied.

• no more lactose is added.

• the amount of

The reaction rate remains constant from point X onwards because:

• the active site of all enzymes is occupied.

• no additional lactose is added.

• the amount of produced product has been completed.

• the enzyme has been denatured.

Pigs are easily infected by the avian flu virus and the human flu virus, which may be present simultaneously in a pig. When this happens, it is possible for genes from the avian flu virus and the human flu virus to combine, thus producing a genetically distinct virus, which can subsequently cause widespread disease. The production of new types of the flu virus in the manner described above resembles more...

• the bottleneck effect.

• the founder effect.

• genetic drift.

• gene flow.

Which diagram correctly depicts a phase of reduction in an organism that has six chromosomes in its somatic cells?

The trinucleotide repeats in a gene are the result of...

• a high mutation rate across the genome.

• extensive duplication of a single codon.

• deviations from the genetic code in human mitochondria.

• the failure of tRNA to recognize specific codons.

Which of the following statements best describes evolution?

• Genetic drift is a random process, but mutations and natural selection are not random.

• Mutations are the only source of genetic variation.

Which of the following statements best describes evolution?

• Genetic drift is a random process, but mutations and natural selection are not random.

• Mutations and genetic drift are random processes, but natural selection is not random.

• Mutations and natural selection are random processes, but genetic drift is not random.

• Natural selection is a random process, but mutations and genetic drift are not random.