Podcast
Questions and Answers
What material makes up the fibre of a chromosome?
What material makes up the fibre of a chromosome?
- Chromatin (correct)
- RNA and proteins
- Histone octamer
- DNA and lipids
Who first observed the structures named 'chromosomes'?
Who first observed the structures named 'chromosomes'?
- Walther Flemming (correct)
- Francis Crick
- Rosalind Franklin
- James Watson
When do chromatin fibres become distinguishable as chromosomes?
When do chromatin fibres become distinguishable as chromosomes?
- During translation
- During apoptosis
- During transcription
- During mitosis (correct)
What are the components of nucleosomes?
What are the components of nucleosomes?
What did Watson and Crick contribute to the study of DNA?
What did Watson and Crick contribute to the study of DNA?
What percentage of histones make up chromatin?
What percentage of histones make up chromatin?
What term describes the complex of DNA and proteins in its coiled form?
What term describes the complex of DNA and proteins in its coiled form?
What are the three components of a nucleotide?
What are the three components of a nucleotide?
Which of the following scientists discovered chromosomes?
Which of the following scientists discovered chromosomes?
What is the primary function of the centromere during cell division?
What is the primary function of the centromere during cell division?
Which nitrogenous base is unique to RNA?
Which nitrogenous base is unique to RNA?
Which components form the structure of a nucleotide?
Which components form the structure of a nucleotide?
In which phase of mitosis do spindle fibres first appear?
In which phase of mitosis do spindle fibres first appear?
During cell division, sister chromatids are separated at the:
During cell division, sister chromatids are separated at the:
During which phase of mitosis does the nuclear membrane reappear?
During which phase of mitosis does the nuclear membrane reappear?
Which of the following sequences encodes particular proteins and is inherited from parents to offspring?
Which of the following sequences encodes particular proteins and is inherited from parents to offspring?
Which structure remains attached to each chromosome during metaphase?
Which structure remains attached to each chromosome during metaphase?
Who proposed the 'double helical' model of DNA?
Who proposed the 'double helical' model of DNA?
What initiates the separation of sister chromatids during mitosis?
What initiates the separation of sister chromatids during mitosis?
What percentage of the human genome is considered 'junk DNA'?
What percentage of the human genome is considered 'junk DNA'?
In which phase does the cleavage furrow start to deepen in an animal cell?
In which phase does the cleavage furrow start to deepen in an animal cell?
At which stage are chromosomes visible as two chromatids joined at the centromere?
At which stage are chromosomes visible as two chromatids joined at the centromere?
What is the primary function of the centromere during cell division?
What is the primary function of the centromere during cell division?
Which of the following best describes sister chromatids?
Which of the following best describes sister chromatids?
DNA fingerprinting is based on variations in which type of DNA?
DNA fingerprinting is based on variations in which type of DNA?
For what purposes can DNA fingerprinting be particularly useful?
For what purposes can DNA fingerprinting be particularly useful?
During which stage of mitosis are sister chromatids detached from each other?
During which stage of mitosis are sister chromatids detached from each other?
What happens to the number of chromosomes during mitosis?
What happens to the number of chromosomes during mitosis?
What is the role of genes on a chromosome?
What is the role of genes on a chromosome?
Why is cell division important for growth?
Why is cell division important for growth?
Which scientist proposed the chemiosmotic hypothesis in 1961?
Which scientist proposed the chemiosmotic hypothesis in 1961?
What results from non-cyclic photophosphorylation?
What results from non-cyclic photophosphorylation?
During the light reaction, which molecule's photolysis occurs?
During the light reaction, which molecule's photolysis occurs?
Where does photosynthetic ATP formation occur?
Where does photosynthetic ATP formation occur?
What is the biosynthetic phase of photosynthesis primarily responsible for?
What is the biosynthetic phase of photosynthesis primarily responsible for?
What process uses oxygen and releases CO₂ in plants?
What process uses oxygen and releases CO₂ in plants?
In which part of the chloroplast are ATP and NADPH used?
In which part of the chloroplast are ATP and NADPH used?
What is the term used for photosynthetic ATP formation?
What is the term used for photosynthetic ATP formation?
Which cells in the human body last a lifetime once formed?
Which cells in the human body last a lifetime once formed?
What is the approximate lifespan of red blood cells?
What is the approximate lifespan of red blood cells?
What is the average lifespan of bone cells in adults?
What is the average lifespan of bone cells in adults?
Which step is NOT a part of karyokinesis?
Which step is NOT a part of karyokinesis?
During which phase of the cell cycle does the division of the nucleus occur?
During which phase of the cell cycle does the division of the nucleus occur?
How often are skin cells replaced in the human body?
How often are skin cells replaced in the human body?
Which type of cell division leads to the production of haploid cells?
Which type of cell division leads to the production of haploid cells?
What happens to the balance of cell production and cell death as humans grow old?
What happens to the balance of cell production and cell death as humans grow old?
Which process occurs during the S-phase of interphase?
Which process occurs during the S-phase of interphase?
What happens to DNA during cell division?
What happens to DNA during cell division?
Which phase involves the synthesis of RNA and proteins necessary for cell division?
Which phase involves the synthesis of RNA and proteins necessary for cell division?
What is the primary activity of the First Growth Phase (G1) in the cell cycle?
What is the primary activity of the First Growth Phase (G1) in the cell cycle?
Which of these cell types is replaced approximately every 120 days?
Which of these cell types is replaced approximately every 120 days?
What occurs during the interphase of the cell cycle?
What occurs during the interphase of the cell cycle?
Which organelles divide during the G1 phase due to having their own DNA?
Which organelles divide during the G1 phase due to having their own DNA?
What is the fate of a cell that withdraws from the cell cycle in late G1 phase?
What is the fate of a cell that withdraws from the cell cycle in late G1 phase?
Which cells in the human body are known to last a lifetime?
Which cells in the human body are known to last a lifetime?
How long does the average life of epithelial cells lining the gut last?
How long does the average life of epithelial cells lining the gut last?
In which stage of animal cell mitosis do chromosomes align at the equatorial plane?
In which stage of animal cell mitosis do chromosomes align at the equatorial plane?
What event marks the beginning of cytokinesis in animal cells?
What event marks the beginning of cytokinesis in animal cells?
Which structure disappears during prophase in both animal and plant cells?
Which structure disappears during prophase in both animal and plant cells?
At what stage do sister chromatids separate and move towards opposite poles in animal cells?
At what stage do sister chromatids separate and move towards opposite poles in animal cells?
During which stage does the cleavage furrow deepen to complete cytokinesis in animal cells?
During which stage does the cleavage furrow deepen to complete cytokinesis in animal cells?
How is the cytoplasm divided in plant cells during cytokinesis?
How is the cytoplasm divided in plant cells during cytokinesis?
Which stage in both animal and plant cells involves the disappearance of spindle fibres?
Which stage in both animal and plant cells involves the disappearance of spindle fibres?
During which stage do chromosomes appear as thread-like structures in both animal and plant cells?
During which stage do chromosomes appear as thread-like structures in both animal and plant cells?
The X-shaped structure formed due to crossing over between the non-sister chromatids of paired homologous chromosomes is called?
The X-shaped structure formed due to crossing over between the non-sister chromatids of paired homologous chromosomes is called?
What process during meiosis results in genetic recombination?
What process during meiosis results in genetic recombination?
Where does mitosis occur in the body?
Where does mitosis occur in the body?
During which phase of mitosis do the chromosomes line up at the cell equator?
During which phase of mitosis do the chromosomes line up at the cell equator?
What key event distinguishes meiosis from mitosis?
What key event distinguishes meiosis from mitosis?
Which nitrogenous base is not found in DNA?
Which nitrogenous base is not found in DNA?
How many daughter cells are produced from one parent cell during mitosis?
How many daughter cells are produced from one parent cell during mitosis?
In which stage of karyokinesis are sister chromatids separated and pulled to opposite poles?
In which stage of karyokinesis are sister chromatids separated and pulled to opposite poles?
Which structure initiates cytokinesis in plant cells?
Which structure initiates cytokinesis in plant cells?
What term describes a full set of chromosomes passed to each daughter cell during mitosis?
What term describes a full set of chromosomes passed to each daughter cell during mitosis?
What type of proteins are primarily associated with chromatin?
What type of proteins are primarily associated with chromatin?
During which phase of the cell cycle do chromatin fibers coil and condense to form chromosomes?
During which phase of the cell cycle do chromatin fibers coil and condense to form chromosomes?
Who was the first scientist to study chromosomes in animals?
Who was the first scientist to study chromosomes in animals?
What year did Rosalind Franklin first work out the shape of the DNA molecule?
What year did Rosalind Franklin first work out the shape of the DNA molecule?
What macromolecule is described as having two complementary strands of nucleotides winding around each other?
What macromolecule is described as having two complementary strands of nucleotides winding around each other?
In which cells did Flemming first observe chromosomes?
In which cells did Flemming first observe chromosomes?
Which of the following best describes the form of chromatin in a non-dividing cell under an electron microscope?
Which of the following best describes the form of chromatin in a non-dividing cell under an electron microscope?
Which scientist is associated with the term 'mitosis'?
Which scientist is associated with the term 'mitosis'?
Which phase does not belong to the interphase of the cell cycle?
Which phase does not belong to the interphase of the cell cycle?
Which components make up each nucleotide in a DNA strand?
Which components make up each nucleotide in a DNA strand?
Study Notes
Structure of Chromosomes
- Chromosomes are discrete units of DNA and proteins, making up chromatin.
- Chromatin is formed of DNA (40%) and histones (60%).
- Each chromosome contains one long DNA molecule and many proteins.
- Chromatin fibres coil and condense to form chromosomes during cell division.
Discovery of Chromosomes
- Walther Flemming first studied chromosomes in animals in 1882.
- He observed minute threads that divided lengthwise, calling their division mitosis.
Structure of DNA
- Rosalind Franklin and James Watson and Francis Crick worked out the double-stranded helical structure of DNA.
- DNA is a macromolecule made up of two complementary strands of nucleotides.
- Each nucleotide consists of phosphate, sugar, and a nitrogenous base.
Nitrogenous Bases
- Purines: Adenine (A) and Guanine (G)
- Pyrimidines: Thymine (T), Cytosine (C), and Uracil (U) (only in RNA)
Chromosome Structure
- Each chromosome has two sister chromatids joined at a centromere.
- Centromere serves as the point of attachment to spindle fibres during cell division.
- Centromere also helps to detach sister chromatids during cell division.
Genes
- Genes are specific sequences of DNA that encode particular proteins.
- Genes are the units of inheritance responsible for specific characteristics.
DNA Fingerprinting
- Regions between genes are known as "junk DNA" and show tremendous variations.
- DNA fingerprinting is useful in establishing paternity and in criminal cases.
Need for New Cells
- Cells are produced for growth, replacement, and repair.
- Cell division ensures the continued existence of an organism.
Mitosis
- Mitosis is a type of cell division that results in two daughter cells with the same number and kind of chromosomes as the parent cell.
- Mitosis occurs in three stages: Interphase, Karyokinesis, and Cytokinesis.
Interphase
- Interphase is the stage where cells grow, synthesise materials, and duplicate DNA.
- Interphase consists of three stages: G1, S, and G2.
Cell Cycle
- The cell cycle is a series of events that take place in a cell leading to the duplication of its DNA and the subsequent division of the cell.
- The cell cycle consists of three stages: G1, S, and G2.
Phases of Mitosis
- Prophase: Chromosomes become visible, nuclear membrane and nucleolus disappear, and spindle fibres appear.
- Metaphase: Chromosomes arrange on the equatorial plane, each attached to a spindle fibre.
- Anaphase: Centromeres divide, separating sister chromatids, and chromatids are drawn apart towards opposite poles.
- Telophase: Daughter chromosomes reach opposite poles, spindle fibres disappear, and a nuclear membrane forms.
Cell Cycle and Cell Division
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The cell cycle can stop temporarily or permanently.
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There is a regulatory mechanism for the cell cycle.
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Cells can be replaced or repaired in various ways, depending on the type of cell.### Significance of Meiosis
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Chromosome number is halved in gametes (sex cells) to restore the normal number of chromosomes (2n) on fertilization.
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Meiosis provides for mixing up of genes through two ways:
- Maternal and paternal chromosomes mixing up during the first (reduction) division as they separate from homologous pairs.
- Crossing over, which results in genetic recombination, occurs when chromatid material is exchanged between non-sister chromatids of paired homologous chromosomes.
Mitosis vs. Meiosis
- Mitosis occurs in somatic/vegetative (body) cells for growth, repair, and replacement.
- Meiosis occurs in reproductive cells for gamete formation only.
- Number of daughter cells produced:
- Mitosis: 2 daughter cells
- Meiosis: 4 daughter cells
- Number of chromosomes passed on to each daughter cell:
- Mitosis: Full set of chromosomes (diploid, 2n)
- Meiosis: Half the number of chromosomes (haploid, n)
- Number of nuclear divisions:
- Mitosis: A single nuclear division after chromosome duplication
- Meiosis: Two nuclear divisions after chromosome duplication
- Identity of chromosomes and genes in daughter cells:
- Mitosis: Identical
- Meiosis: Randomly assorted between gametes, resulting in genetic variations
Cell Structure and Division
- Chromosomes are formed of very long fine DNA molecule wrapped around histone proteins.
- Nucleosomes are groups of histone molecules with DNA wrapped around them.
- Each DNA strand is composed of repeating nucleotides.
- The four nitrogenous bases are adenine, guanine, thymine, and cytosine.
- During replication, the DNA double helix gets unwound and separated.
- Genes are specific sequences of nucleotides.
- New cells need to be produced for growth and replacement.
- Mitosis involves duplication of chromosomes, maintaining the chromosome number in all cells.
- Mitosis occurs in two phases: Karyokinesis and Cytokinesis.
- Karyokinesis occurs in four steps: prophase, metaphase, anaphase, and telophase.
- Cytokinesis: In animal cells, by deepening of a furrow; in plant cells, a cell plate appears across the center.
- Meiosis involves two divisions, reducing the number of chromosomes to half.
- Meiosis also involves crossing over, resulting in genetic variations.
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Description
This quiz covers the structure of chromosomes, cell cycle phases including interphase and mitotic phase, and the process of cell division including mitosis and meiosis. It also touches on the significance and differences between these types of cell division.
