CBSE Questions for Class 9 Biology The Fundamental Unit Of Life Quiz 4 - MCQExams.com

• The endoplasmic reticulum is a complex yet well-organized organelle of the eukaryotic cell. 
• It plays a major role in the manufacturing and packaging of proteins.
• ER is of 2 types:

1. Rough endoplasmic reticulum - It consists of ribosomes on its external surface, thus giving it a rough appearance and is responsible for protein synthesis.
2. Smooth endoplasmic reticulum - It doesn't have ribosomes and is smooth in appearance, its main function is to produce cellular products like hormones and lipids. 

• Chromatin is a complex of DNA and proteins that form chromosomes within the nucleus of eukaryotic cells. Nuclear DNA does not appear in free linear strands. It is highly condensed and wrapped around nuclear proteins in order to fit inside the nucleus.
• Mitochondria, ribosomes, endoplasmic reticulum and centriole are found inside the nucleus, but outside the nucleus.

Correct answer: B
Explanation:

• The odd one out of the following options is the gamete. The chromosome, nucleus and gene are the parts of the DNA.
• The chromosomes are the condensed form of DNA and histones.
• The nucleus is the site where the DNA is present and the gene is the segment of DNA that encodes for the proteins.
• The gamete is the haploid cell that is produced by the meiotic division of the germ cells

• A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. The term is also used for the complete set of chromosomes in a species or in an individual organism. The study of whole sets of chromosomes is sometimes known as karyology. Hence, the karyology is the study of the nucleus.
  
• So, the correct answer is 'nucleus'.
  

• Eukaryotes are more complex than prokaryotes in their body organization as well as the genetic material. It is because the eukaryotes have a nucleus in which genetic material is found separated from the cytoplasm. They also have more DNA than prokaryotes.
• In contrast, prokaryotes are simple. They do not have any nucleus, in absence of which their genomes are less complex. 

• The endoplasmic reticulum is a membranous network present in the eukaryotic cells. 
• It is of two types such as smooth endoplasmic reticulum (absence of ribosomes) and rough endoplasmic reticulum (presence of ribosome). 
• The endoplasmic reticulum is responsible for the formation and transportation of proteins and lipids. 

• Robert Brown was a Scottish life scientist and paleobotanist who discovered the nucleus and discovered that each and every animal are the product of cells. 
• The cell nucleus​ could be a membrane-shaped structure that consists of a cell's hereditary statistics and controls its extension and copy.
•  It is the command center of a organism cell and is typically the foremost notable cell organ in each size and performance.
•  Hence, Nucleus was discovered by Robert Brown.

• Hammerling's nucleocytoplasmic experiments state that the cytoplasm is the centre for all the metabolic activities in the cell and the nucleus is the controlling centre. 

• This experiment was conducted using Acetabularia.

• Acetabularia is a genus unicellular or single-celled green algae belonging to the family Polyphysaceae which are found in subtropical waters.

• They are gigantic in size and complex in form, therefore, used in experiments in cell biology.

• So, the correct answer is 'Acetabularia'.

• The nuclear membrane or karyotheca is a double membrane having pores at intervals.
• The nuclear membrane on its inside has a supporting membrane called the nuclear lamina or the fibrous lamina having a uniform thickness.
• It is a dense network of fibres present inside the nucleus of cells and are made up of intermediate filaments and membrane-associated proteins.
• It provides mechanical support to the nucleus and also regulates DNA replication and cell division 
• So, the correct answer is 'Both B and C.'

• The DNA present in the nucleus undergoes transcription to form the messenger RNA or mRNA.
  
• The mRNA formed within the nucleus is transported out of the nucleus and into the cytoplasm of the cell and gets attached to the ribosomes. 
• It then synthesis proteins in the cytoplasm which is required by the cell for various cellular activities.
• So, the correct answer is 'RNAs'.