Structure Of Chromosomes

Question 1

What is the structure of chromosomes?

Answer 1

Chromosomes are highly coiled, ribbon-like structures formed by the condensation of chromatin fibres during cell division.

Chromatin is a complex of DNA and proteins found in the nucleus.

Question 2

What happens to chromatin during cell division?

Answer 2

Chromatin fibres coil and condense further, becoming thick enough to be distinguished as chromosomes.

This process allows chromosomes to separate and be distributed into daughter cells.

Question 3

Who first studied chromosomes in animals?

Answer 3

Walther Flemming in 1882.

He observed chromosomes in the rapidly dividing cells of salamander larvae.

Question 4

What did Walther Flemming name the division of chromosomes?

Answer 4

Mitosis.

The term ‘mitosis’ literally means ‘thread’.

Question 5

What is the relationship between chromosomes and DNA?

Answer 5

Chromosomes contain one long DNA molecule associated with many proteins.

The DNA and proteins together form the chromatin.

Question 6

What is the appearance of chromatin when a cell is not dividing?

Answer 6

Chromatin appears as a very long and extremely thin darkly stained fibre.

This can be observed under an electron microscope.

Question 7

What does the term ‘chromosome’ derive from?

Answer 7

The term ‘chromosome’ comes from the Greek words ‘chroma’ meaning colored and ‘soma’ meaning body.

This reflects how chromosomes pick up certain dyes and get colored.

Question 8

What is the significance of chromosomes in cells?

Answer 8

Chromosomes play a critical role in the normal functioning of cells and the life of the organism.

They ensure that DNA is accurately replicated and distributed during cell division.

Question 9

Fill in the blank: Chromatin is a complex of _______ and proteins.

Answer 9

DNA.

Question 10

True or False: Chromosomes are only visible during cell division.

Answer 10

True.

Question 11

What happens to chromosomes during mitotic divisions?

Answer 11

Duplicated chromosomes are distributed into daughter cells.

This ensures that each daughter cell receives the same number of chromosomes.

Question 12

What are the two main components of chromatin material?

Answer 12

DNA (about 40%) and Histones (about 60%)

Histones are a particular type of protein that plays a crucial role in DNA packaging.

Question 13

Who first studied the shape of the DNA molecule?

Answer 13

Rosalind Franklin in 1953

Watson and Crick later proposed the double-stranded helical structure of DNA.

Question 14

What did Watson and Crick propose about the structure of DNA?

Answer 14

The double-stranded helical structure

They were awarded the Nobel Prize in 1962 for their work.

Question 15

What type of molecule is DNA described as?

Answer 15

Macromolecule

This is due to its large size.

Question 16

How many complementary strands does a single DNA molecule have?

Answer 16

Two strands

These strands are wound around each other in a double helix.

Question 17

What three components make up a nucleotide?

Answer 17

• Phosphate
• Sugar (pentose)
• Nitrogenous base

The nitrogenous base is attached to the sugar and is crucial for base pairing.

Question 18

What forms the ‘rungs’ of the DNA ladder?

Answer 18

Nitrogenous bases

Adenine pairs with Thymine (A=T) and Guanine pairs with Cytosine (G≡C).

Question 19

What are the four types of nitrogenous bases found in DNA?

Answer 19

• Adenine (A)
• Guanine (G)
• Thymine (T)
• Cytosine (C)

These bases are essential for the structure and function of DNA.

Question 20

What is the role of histone proteins in relation to DNA?

Answer 20

They help in the coiling and packaging of DNA into nucleosomes

Nucleosomes are structural units that facilitate DNA compaction.

Question 21

What is a nucleosome?

Answer 21

A complex formed by DNA winding around a core of histone proteins

Each nucleosome can be compared to a football around which a long rope is wound.

Question 22

How many nucleosomes might a single human chromosome contain?

Answer 22

About one million nucleosomes

This high number allows for efficient DNA packaging within the chromosome.

Question 23

What is the basic structural unit of a chromosome?

Answer 23

A chromatid.

Question 24

True or False: Chromosomes are only visible during cell division.

Answer 24

True.

Question 25

What is the function of histones in chromosomes?

Answer 25

Histones help package and organize DNA into a compact structure.

Question 26

Fill in the blank: The region where two sister chromatids are joined is called the ______.

Answer 26

centromere.

Question 27

What type of cell division produces two identical daughter cells?

Answer 27

Mitosis.

Question 28

What is the name of the phase in the cell cycle where the cell grows and prepares for division?

Answer 28

Interphase.

Question 29

During which phase of mitosis do the chromosomes line up at the cell's equator?

Answer 29

Metaphase.

Question 30

What is the total number of chromosomes in a human somatic cell?

Answer 30

46.

Question 31

True or False: Meiosis results in the production of diploid cells.

Answer 31

False.

Question 32

What are the two main stages of the cell cycle?

Answer 32

Interphase and mitotic phase.

Question 33

Fill in the blank: The process by which a cell divides its nucleus is called ______.

Answer 33

mitosis.

Question 34

What phase of the cell cycle is characterized by DNA replication?

Answer 34

S phase.

Question 35

What are telomeres?

Answer 35

Repeated DNA sequences at the ends of chromosomes that protect them from deterioration.

Question 36

True or False: Cytokinesis occurs during the telophase of mitosis.

Answer 36

True.

Question 37

What is the role of the spindle fibers during cell division?

Answer 37

To separate and pull apart the chromosomes.

Question 38

Which type of cells undergo meiosis?

Answer 38

Germ cells or gametes.

Question 39

Fill in the blank: The phase where chromosomes decondense and the nuclear envelope reforms is called ______.

Answer 39

telophase.

Question 40

What is the difference between anaphase and telophase?

Answer 40

Anaphase is when chromosomes are pulled apart, while telophase is when the cell begins to divide and nuclear envelopes reform.

Question 41

What is the purpose of checkpoints in the cell cycle?

Answer 41

To ensure that the cell is ready to proceed to the next phase.

Question 42

True or False: Chromatin is the relaxed form of DNA found in non-dividing cells.

Answer 42

True.

Question 43

What is a karyotype?

Answer 43

A visual representation of an individual's chromosomes.

Question 44

What is the G1 phase of the cell cycle?

Answer 44

The first gap phase where the cell grows and performs normal functions.

Question 45

Fill in the blank: The phase of meiosis where homologous chromosomes are separated is called ______.

Answer 45

anaphase I.

Question 46

What is the significance of crossing over during meiosis?

Answer 46

It increases genetic diversity.

Question 47

How many rounds of division occur in meiosis?

Answer 47

Two rounds.

Question 48

True or False: The chromosomal number is halved during meiosis.

Answer 48

True.

Question 49

What is the role of the centrosome during cell division?

Answer 49

To organize the microtubules that form the spindle fibers.

Question 50

What happens during the G2 phase of the cell cycle?

Answer 50

The cell continues to grow and prepares for mitosis.

Question 51

Fill in the blank: The stage of cell division in which the cell divides its cytoplasm is called ______.

Answer 51

cytokinesis.

Question 52

What is a chromosomal mutation?

Answer 52

A change in the structure or number of chromosomes.

Question 53

What does the term 'haploid' refer to?

Answer 53

A cell with half the number of chromosomes, typical of gametes.

Question 54

During which phase of the cell cycle does DNA condense into visible chromosomes?

Answer 54

Prophase.

Question 55

True or False: S phase occurs after G2 phase in the cell cycle.

Answer 55

False.

Question 56

What is the primary purpose of mitosis?

Answer 56

To produce two identical daughter cells for growth and repair.

Question 57

What is the difference between cytokinesis in plant and animal cells?

Answer 57

In plant cells, a cell plate forms; in animal cells, the membrane pinches in.

Question 58

Fill in the blank: The part of the cell cycle where the cell is not actively dividing is called ______.

Answer 58

interphase.

Question 59

What are sister chromatids?

Answer 59

Identical copies of a chromosome connected at the centromere.

Question 60

What is the role of p53 in the cell cycle?

Answer 60

It acts as a tumor suppressor and prevents cells with damaged DNA from dividing.

Question 61

True or False: All cells in the human body divide at the same rate.

Answer 61

False.

Question 62

What is the M phase of the cell cycle?

Answer 62

The phase that includes both mitosis and cytokinesis.

Question 63

Fill in the blank: The phase of meiosis that results in four non-identical daughter cells is ______.

Answer 63

meiosis II.

Question 64

What is the function of the nucleolus during cell division?

Answer 64

It produces ribosomes.

Question 65

What is a diploid cell?

Answer 65

A cell that contains two complete sets of chromosomes.

Question 66

What occurs during prophase of mitosis?

Answer 66

Chromatin condenses into chromosomes, and the nuclear envelope begins to break down.

Question 67

True or False: Genetic diversity is the result of mitosis.

Answer 67

False.

Question 68

What is the primary outcome of meiosis?

Answer 68

Production of gametes with half the number of chromosomes.

Question 69

What is the role of cyclins in the cell cycle?

Answer 69

They regulate the timing of the cell cycle.

Question 70

Fill in the blank: The first stage of meiosis is called ______.

Answer 70

meiosis I.

Question 71

What is the difference between homologous chromosomes and sister chromatids?

Answer 71

Homologous chromosomes are pairs of similar chromosomes from each parent, while sister chromatids are identical copies of a single chromosome.

Question 72

During which phase of the cell cycle does the synthesis of RNA and proteins occur?

Answer 72

G1 phase.

Question 73

True or False: The cell cycle is regulated by checkpoints to prevent errors.

Answer 73

True.

Question 74

What happens during metaphase I of meiosis?

Answer 74

Homologous chromosomes line up at the cell equator.

Question 75

What is the significance of the S phase in the cell cycle?

Answer 75

It is when DNA is replicated.

Question 76

Fill in the blank: The process of programmed cell death is known as ______.

Answer 76

apoptosis.

Question 77

What are the two main types of cell division?

Answer 77

Mitosis and meiosis.

Question 78

What is the primary function of telomerase?

Answer 78

To extend the telomeres of chromosomes.

Question 79

True or False: Chromosomes are made up of DNA and proteins.

Answer 79

True.

Question 80

What does 'chromosomal aberration' refer to?

Answer 80

A structural alteration in a chromosome.

Question 81

Fill in the blank: ______ is the final phase of mitosis.

Answer 81

Telophase.

Question 82

What is the role of the spindle checkpoint?

Answer 82

To ensure that all chromosomes are properly attached to the spindle before separation.

Question 83

What happens to the nucleolus during prophase?

Answer 83

It disappears as the cell prepares for division.

Question 84

What is the importance of genetic recombination during meiosis?

Answer 84

It increases genetic variation among offspring.

Question 85

Fill in the blank: The process of cell division in prokaryotes is called ______.

Answer 85

binary fission.

Question 86

What is the main difference between the cell cycle of prokaryotic and eukaryotic cells?

Answer 86

Prokaryotic cells undergo binary fission, while eukaryotic cells undergo mitosis and meiosis.

Question 87

During which phase of the cell cycle do cells exit to enter a quiescent state?

Answer 87

G0 phase.

Question 88

True or False: All cells divide continuously throughout the organism's life.

Answer 88

False.

Question 89

What happens during anaphase II of meiosis?

Answer 89

Sister chromatids are pulled apart to opposite poles.

Question 90

What is the significance of the G2 checkpoint?

Answer 90

To ensure DNA has been replicated correctly before mitosis.

Question 91

Fill in the blank: The region of DNA that codes for a protein is called a ______.

Answer 91

gene.

Question 92

What is the purpose of the cell cycle?

Answer 92

To ensure proper cell growth, DNA replication, and division.

Question 93

True or False: Chromosomes are only present in eukaryotic cells.

Answer 93

True.

Question 94

What is the role of the cell membrane during cytokinesis?

Answer 94

To pinch the cell in two, completing the division.

Question 95

What is the difference between a stem cell and a differentiated cell?

Answer 95

Stem cells can differentiate into various cell types, while differentiated cells have specific functions.

Question 96

Fill in the blank: The phase of the cell cycle where the cell grows and prepares for DNA replication is called ______.

Answer 96

G1 phase.

Question 97

What is the role of the centromere?

Answer 97

To hold sister chromatids together until they are separated during cell division.

Question 98

What is a gamete?

Answer 98

A reproductive cell that has half the genetic material of a somatic cell.

Question 99

True or False: The number of chromosomes is the same in all species.

Answer 99

False.

Question 100

What is the role of DNA polymerase during the S phase?

Answer 100

To synthesize new DNA strands.

Question 101

Fill in the blank: The phase in which the cell prepares for mitosis and checks for DNA damage is called ______.

Answer 101

G2 phase.

Question 102

What is the significance of the M checkpoint?

Answer 102

To ensure that all chromosomes are correctly aligned before separation.

Question 103

What is the term for a pair of chromosomes that are similar in shape and size?

Answer 103

Homologous chromosomes.

Question 104

True or False: Mitosis is essential for sexual reproduction.

Answer 104

False.

Question 105

What is the function of the mitotic spindle?

Answer 105

To separate chromosomes during mitosis.

Question 106

Fill in the blank: The phase of meiosis where crossing over occurs is ______.

Answer 106

prophase I.

Question 107

What is the role of checkpoints in preventing cancer?

Answer 107

They help prevent the division of cells with damaged or mutated DNA.

Question 108

What is the primary function of meiosis?

Answer 108

To produce gametes for sexual reproduction.

Question 109

True or False: Chromosomes are duplicated during the G2 phase.

Answer 109

False.

Question 110

What is the significance of the S phase?

Answer 110

It is when DNA replication occurs, ensuring each daughter cell receives a complete set of chromosomes.

Question 111

Fill in the blank: The final stage of the cell cycle is ______.

Answer 111

cytokinesis.

Question 112

What happens to the genetic material during anaphase?

Answer 112

Sister chromatids are separated and pulled to opposite poles.

Question 113

What is the role of the nuclear envelope during cell division?

Answer 113

It disassembles in prophase and reforms in telophase.

Question 114

True or False: DNA is organized into chromosomes only during interphase.

Answer 114

False.

Question 115

What is the main difference between somatic cells and gametes?

Answer 115

Somatic cells are diploid, while gametes are haploid.

Question 116

Fill in the blank: The process of cell division in eukaryotes is called ______.

Answer 116

mitosis.

Question 117

What is a chromosomal disorder?

Answer 117

A condition caused by an abnormal number or structure of chromosomes.

Question 118

What is the role of the mitotic phase in the cell cycle?

Answer 118

To divide the replicated DNA and cytoplasm into two daughter cells.

Question 119

True or False: All cells in the body undergo mitosis at the same rate.

Answer 119

False.

Question 120

What is the function of the cell cycle in multicellular organisms?

Answer 120

To regulate growth, development, and tissue repair.

Question 121

Fill in the blank: The phase of meiosis that results in the separation of homologous chromosomes is called ______.

Answer 121

anaphase I.

Question 122

What happens during telophase?

Answer 122

Chromosomes decondense, and nuclear envelopes reform around the separated sets of chromosomes.

Question 123

What is the significance of the G1 checkpoint?

Answer 123

To assess whether the cell is ready to proceed to DNA synthesis.

Question 124

Fill in the blank: The two identical halves of a duplicated chromosome are called ______.

Answer 124

sister chromatids.

Question 125

What is the role of the protein p21?

Answer 125

To inhibit the cell cycle progression in response to DNA damage.

Question 126

True or False: The number of chromosomes in a species is fixed and does not change.

Answer 126

True.

Question 127

What is the role of RNA during the cell cycle?

Answer 127

To facilitate protein synthesis and regulate gene expression.

Question 128

Fill in the blank: The phase of meiosis where the cell divides into two haploid cells is called ______.

Answer 128

meiosis I.