Identify the correct statement about the cell nucleus:
A. It is absent in all eukaryotic cells.
B. DNA replication occurs in the cytoplasm.
C. It contains the nucleolus, which synthesizes ribosomal RNA.
D. It is surrounded by a single membrane.
Answer: Option C
Solution (By JKSSB Mock Tests)
The nucleolus makes rRNA and assembles ribosomal subunits. Nucleus has a double membrane, is present in eukaryotes, and is the site of DNA replication.
Explanation:
The sinoatrial (SA) node, located in the right atrium, generates electrical impulses spontaneously and initiates each heartbeat, setting the rhythm. It is called the natural pacemaker. The atrioventricular (AV) node delays the impulse before it travels to the ventricles. The bundle of His and Purkinje fibers conduct the impulse through the ventricles.
Explanation:
In aquatic plants like Hydrilla, the rate of photosynthesis can be estimated by counting the number of oxygen bubbles released per minute under light. Manometry measures pressure changes, respirometry respiration, spectrophotometry light absorbance.
Explanation:
Human somatic cells are diploid (2n = 46), with 23 pairs of homologous chromosomes. Gametes (sperm and egg) are haploid (n = 23), containing one set of chromosomes. Fertilization restores diploidy. The haploid number is 23. Option 22 would be autosomes plus one sex chromosome, but the total count is 23. 44 is the number of autosomes in somatic cells.
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