Why does a cell grow before it divides?

So that it can make extra sub-cellular structures such as mitochondria and ribosomes for the two cells it will become.

What happens to the copied chromosomes in mitosis?

They are pulled apart to opposite ends of the cell, so each new nucleus receives a full set.

How many cells does one round of mitosis produce, and how do they compare with the parent cell?

Two cells, each genetically identical to the parent cell and to each other.

Give two roles of mitosis in a multicellular organism.

Growth, and the repair or replacement of damaged cells.

OCR GCSE Combined Science Biology J250

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

Community Level Systems

Topic overview Cycling materials, and the role of microorganisms The carbon and water cycles, and decomposition Levels of organisation, and abiotic and biotic factors Interdependence, competition, mutualism and parasitism

Genes, Inheritance and Selection

Topic overview Genetic terms, and the genome Genome, environment and mutations Haploid, diploid and meiosis Single gene inheritance and Punnett squares Sex determination and characteristics controlled by many genes Variation within a population, and classification Natural selection and evolution Evidence for evolution from fossils and antibiotic resistance

Global Challenges

Topic overview Field investigations, and human impact on ecosystems Maintaining biodiversity, monitoring conservation and ecotourism Selective breeding and genetic engineering Health, disease, and types of disease Interactions between diseases, and how they spread Reducing the spread of disease, and named examples White blood cells, antibodies and platelets Non-specific defences and the immune system Vaccines, medicines and aseptic technique Developing new medicines, and non-communicable disease Treating cardiovascular disease, and lifestyle factors Cancer, and the use of stem cells in medicine Gene technology in medicine, and the human genome

Organism Level Systems

Topic overview The nervous system and coordinated responses The reflex arc Hormones and the endocrine glands Hormones in reproduction and the menstrual cycle Methods of contraception Homeostasis and control systems in the body Insulin and the control of blood glucose Type 1 and type 2 diabetes

Scaling Up

Topic overview Diffusion, osmosis and active transport Mitosis, the cell cycle and cell differentiation Stem cells in animals and meristems in plants Surface area to volume ratio and exchange surfaces The circulatory system, the heart and blood vessels Red blood cells and plasma Root hair cells, transpiration and translocation Xylem and phloem Factors affecting water uptake, and the potometer

Scaling Up

Mitosis, the cell cycle and cell differentiation

3 things to know
Paper 1 (Biology)

Overview

The stages of the cell cycle, DNA replication and why cells grow first, what happens to chromosomes in mitosis and the two identical cells it makes, its roles in growth, repair and asexual reproduction, what cell differentiation is and why it makes organisms efficient, how sperm, nerve, muscle and palisade cells are specialised, how plant and animal cells differ in keeping that ability, and reading percentiles on growth charts.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What happens to the chromosomes when DNA is replicated, what does one round of mitosis produce, and what is mitosis for in a multicellular organism?

Process

List the stages of the cell cycle in order.

Key term

What happens to the chromosomes during DNA replication?

Questions from this subtopic

Each one with the model answer underneath.

1
List the stages of the cell cycle in order.
Model answer
The cell grows, its DNA is replicated, the cell grows again, and finally the chromosomes are moved apart as the cell divides.
2
What happens to the chromosomes during DNA replication?
Model answer
Every chromosome is copied, so the cell holds two identical copies of each one.
3
Why does a cell grow before it divides?
Model answer
So that it can make extra sub-cellular structures such as mitochondria and ribosomes for the two cells it will become.
4
What happens to the copied chromosomes in mitosis?
Model answer
They are pulled apart to opposite ends of the cell, so each new nucleus receives a full set.
5
How many cells does one round of mitosis produce, and how do they compare with the parent cell?
Model answer
Two cells, each genetically identical to the parent cell and to each other.
6
Give two roles of mitosis in a multicellular organism.
Model answer
Growth, and the repair or replacement of damaged cells.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

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AA diet high in sugar and fat leads to obesity.

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Homozygous means carrying two identical alleles of a gene.

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