Cell Division Flashcards

All 18 cards in this deck

Where in a cell are the chromosomes found?

In the nucleus.

What are chromosomes made of?

DNA molecules.

What does each chromosome carry?

A large number of genes.

How are chromosomes normally arranged in body cells?

In pairs.

Put these in order, largest first: gene, nucleus, chromosome.

Nucleus, chromosome, gene.
The nucleus contains chromosomes, and each chromosome carries many genes.

Name the type of cell division that produces genetically identical body cells for growth and repair.

Mitosis.

Why are the two cells produced by mitosis genetically identical?

The DNA is replicated first, so one identical set of chromosomes is pulled to each end of the cell.

Why is cell division by mitosis important in multicellular organisms?

For growth and development, and for repairing or replacing damaged cells.
e.g. growth of an embryo, healing of a wound, growth of a plant root tip.

What are the steps to work out the percentage of the cell cycle taken up by one stage?
e.g. a stage lasts 3 hours in a 12-hour cell cycle

1. Divide the stage time by the total cycle time: $3 \div 12 = 0.25$
2. Multiply by 100: $0.25 \times 100 = 25\%$

True or false? Mitosis produces cells with half the number of chromosomes of the parent cell.

False.
Mitosis produces two cells with the same number of chromosomes as the parent cell, genetically identical to it.

What is a stem cell?

An undifferentiated cell that can give rise to many more cells of the same type, and from which certain other cell types can arise by differentiation.

What is the name of the process by which a stem cell becomes a specialised cell?

Differentiation.

True or false? Stem cells from adult bone marrow can differentiate into any type of human cell.

False.
Adult bone marrow stem cells form many types of cell including blood cells, whereas embryonic stem cells can be made to differentiate into most types of human cell.

In therapeutic cloning, why are the stem cells not rejected by the patient's body?

The embryo produced has the same genes as the patient, so its stem cells are not rejected and may be used for treatment.

Give one benefit and one risk or objection to using stem cells in medicine.

Benefit: treatment may help conditions such as diabetes and paralysis.
Risk/objection: transfer of viral infection, and some people have ethical or religious objections.

What can stem cells from plant meristems do, and why are they useful?

They can differentiate into any type of plant cell throughout the plant's life, so they can produce clones of plants quickly and economically.
e.g. preserving rare species or producing disease-resistant crops.

What are the steps of the cell cycle that produce two identical cells?

e.g. a skin cell dividing into two

1. Growth: the cell grows, the number of sub-cellular structures (ribosomes, mitochondria) increases and the DNA replicates to form two copies of each chromosome.
2. Mitosis: one set of chromosomes is pulled to each end of the cell and the nucleus divides.
3. The cytoplasm and cell membranes divide — giving two identical skin cells.

Other than DNA replication, what happens to a cell in the first (growth) stage of the cell cycle?

The cell grows and increases the number of sub-cellular structures such as ribosomes and mitochondria.