16.1 Nuclear Division (Cambridge (CIE) O Level Biology): Flashcards
Exam code: 5090
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- FrontChromosomes & Cells
Define chromosome.
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Define chromosome.
A thread-like structure of DNA, found in the nucleus, that carries genetic information in the form of genes.
Define gene.
A short length of DNA on a chromosome that codes for a specific protein.
Define allele.
A different version of a particular gene.
Define inheritance.
The transmission of genetic information from generation to generation.
Where in a cell are chromosomes found?
In the nucleus.
What does a gene code for?
A specific protein, such as an enzyme, a hormone or a structural protein like collagen.
The nucleus of a gamete is and contains half the number of chromosomes of a body cell.
The nucleus of a gamete is haploid and contains half the number of chromosomes of a body cell.
In humans, a haploid gamete nucleus contains chromosomes.
In humans, a haploid gamete nucleus contains 23 chromosomes.
How many chromosomes are found in a human diploid cell?
46 chromosomes (23 pairs).
True or False?
A diploid cell has two copies of each chromosome.
True.
A diploid cell has two copies of each chromosome, whereas a haploid cell has only one copy of each.
True or False?
Alleles are the structures that carry chromosomes.
False.
Alleles are different versions of a gene; chromosomes are the structures that carry genes.
Define mitosis.
Nuclear division giving rise to genetically identical cells.
Define diploid.
A cell that has two copies of each chromosome.
Define stem cell.
An unspecialised cell that divides by mitosis to produce cells that can become specialised.
Why do chromosomes copy themselves before mitosis?
So that each new cell receives a full copy of every chromosome and stays diploid.
Give three roles of mitosis in organisms.
Mitosis is used for:
growth
repair of damaged tissues
asexual reproduction
What happens to the chromosomes during mitosis?
Each chromosome copies itself, the copies line up along the centre of the cell, and cell fibres pull them apart before the cell divides in two.
Mitosis produces two daughter cells that are genetically to each other and to the parent cell.
Mitosis produces two daughter cells that are genetically identical to each other and to the parent cell.
The ultimate stem cell is the , which divides to form a ball of embryonic stem cells.
The ultimate stem cell is the zygote, which divides to form a ball of embryonic stem cells.
True or False?
Mitosis produces cells that are genetically identical to the parent cell.
True.
Mitosis is nuclear division that produces genetically identical daughter cells.
True or False?
Gametes are produced by mitosis.
False.
Gametes are produced by meiosis; mitosis produces the other body cells.
Why are stem cells important in the body?
They divide by mitosis and can become specialised, allowing growth and the replacement of cells.
Define meiosis.
A type of nuclear division that produces genetically different cells and halves the chromosome number.
Define haploid.
Describes a cell (gamete) with half the chromosome number of a body cell — one copy of each chromosome.
Define reduction division.
A division in which the chromosome number is halved from diploid to haploid.
Why must the chromosome number be halved when gametes are made?
So that when two gametes fuse at fertilisation, the zygote has the correct diploid number and it does not double each generation.
How many daughter cells does meiosis produce, and what type are they?
Four cells, each haploid and genetically different.
What type of cells does meiosis produce?
Gametes (sex cells).
How does meiosis increase genetic variation?
It creates new combinations of maternal and paternal chromosomes in each gamete, so offspring differ when gametes fuse.
Meiosis involves divisions, producing four haploid daughter cells.
Meiosis involves two divisions, producing four haploid daughter cells.
Meiosis produces daughter cells that are genetically from one another.
Meiosis produces daughter cells that are genetically different from one another.
True or False?
Meiosis produces four genetically identical daughter cells.
False.
Meiosis produces four genetically different, haploid cells; mitosis is the division that produces identical cells.
True or False?
Gametes are haploid cells.
True.
Gametes contain half the chromosome number of a body cell — one copy of each chromosome.
Define tumour.
A mass of cells formed by uncontrolled cell division.
Define mutation.
A change in the DNA of a cell.
What causes cancer?
Mutations in the DNA of cells that lead to uncontrolled cell growth and division.
Why do healthy cells divide only when needed?
The cell cycle is controlled by many genes that determine when cells divide and when they stop.
How can uncontrolled cell division form a tumour?
Cells divide repeatedly and uncontrollably, producing a mass of cells (a tumour).
By which type of cell division do body cells divide for growth and repair?
Mitosis.
Cancer results from a loss of control of the , causing uncontrolled cell division.
Cancer results from a loss of control of the cell cycle, causing uncontrolled cell division.
A mass of cells produced by uncontrolled cell division is called a .
A mass of cells produced by uncontrolled cell division is called a tumour.
True or False?
Cancer is caused by uncontrolled cell division.
True.
Mutations in DNA can cause cells to divide uncontrollably, forming a tumour.
True or False?
Tumours form when the cell cycle is too tightly controlled.
False.
Tumours form when control of the cell cycle is lost, allowing uncontrolled cell division.
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