Topic 1: Mitosis

What does the nucleus cell contain

chromosomes made of DNA molecules

Explain why chromosomes in body cells are normally found in pairs.

One set is inherited from the organisms mother and one from its father

What areChromosomes

Chromosomes are long lengths of a molecule called DNA, the DNA is coiled up to form the arms of the chromosome

What doChromosomes carry

Each chromosome carries a large number of genes. These are short sections of DNA. Genes control our characteristics. Different genes control the development of different characteristics, eg hair colour, eye colour.

Why do gametes (sperm + ovum cells) have half the normal number of chromosomes

They combine to make a full set (fertilisation)

What are chromosomes made of and contain

Made of:

• DNA

Contain:

• sections called genes

What is the function of a gene

coding for characteristics

what is an allele

half a gene/different form

What is the function of DNA

codes for protein

Label genetic material of a cell

What are the 4 bases in DNA

(A,T,C,G)

• Adenine

• Thymine

• Cytosine

• Guanine

Define mitosis

cell division

Describe situations where mitosis is occurring

• Asexual Reproduction - A plant or animal makes a copy of itself without a mate

• Growth - When a child grows taller, their body cells divide to make more cells

• Healing wounds + replacing old cells - your body fixes cuts and wounds, your skin, hair, and nails grow new cells

• Development - A baby grows from one tiny cell after fertilization

• Regeneration - Some animals grow back lost parts

How many cells are produced during mitosos

2

What do body cells in multicellular organisms do

Divide to produce new cells as part of a series of stages called the cell cycle

What is meant by the cell cycle

when the cells grow + divide

When does the cell cycle start and when does it end

Starts - when a cell has been produced by cell division

Ends - with the cell dividing to produce two identical cells

What is the stage of the cell cycle called when the cell divides

Mitosis

During which period of the cell cycle does cell growth occur

Interphase

Why is the cell cycle needed

• to grow

• repair

• Asexual reproduction

Stages of Mitosis

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

Interphase

• Parent Cell

• Cell growth

• DNA replication

Prophase

Chromosomes make identical copies of themselves

Metaphase

Chromosomes line up along the center (equator)

Anaphase

Chromosomes are pulled apart to poles

Telophase

Cells divide into two identical daughter cells

How cell division by mitosis is important in the growth, repair, and development of multicellular organisms

• Growth - When an organism grows, it’s cells divide through mitosis to create more cells , allowing tissues + organs to expand

• Development - From a single fertilised egg (zygote), mitosis creates all the different cells that make up the organism

• Repair - Mitosis helps replace damages or dead cells

Which stage do cells spend more time in - mitosis or cell growth

Cell growth

steps of the cell cycle

1. During the cell cycle, the genetic material is doubled and then divided into two identical cells.

2. Before a cell can divide, it needs to grow and increase the amount of subcellular structures such as ribosomes and mitochondria.

3. The DNA replicates to form two copies of each chromosome.

4. In mitosis, one set of chromosomes is pulled to each end of the cell, and the nucleus divides.

5. Finally the cytoplasm and cell membranes divide to form two identical cells.

What are the results of the steps of the cell cycle

The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA - they’re identical. Their DNA is also identical to the parent cell.

Explain how using tissue culture creates a clone of a plant

The stem cells allow the small pieces of tissues to grow into full organisms

What is a stem cell

An undifferentiated cell that can replicate itself and differentiate to become a specialised cell

Where do we find stem cells

In a bone marrow or embryos

Where do stem cells grow

plants meristems

What can stem cells from human embryos, adult bone marrow and the meristems in plants do

• Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.

• Stem cells from adult bone marrow can form many types of cells, including blood cells.

• Meristem tissue in plants can differentiate into any type of plant cell throughout the life of the plant.

Describe differences between embryonic and adult stem cells.

• Embryonic stem cells are only found in embryos, whereas adult stem cells are found in adults and children

• Embryonic stem cells can differentiate into all the cell types that make up a human, whereas adult stem cells can only differentiate into certain ones, such as blood cells

• In medicine, embryonic stem cells could be used to replace faulty cells in sick people in the future, whereas in medicine, adult stem cells are already used to cure disease

Describe what therapeutic cloning can be used for

In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.

Arguments for and against stem cell research

For:

• Curing patients who already exist and who are suffering is more important than the rights of embryos

• The embryos used in the research are usually unwanted ones from fertility clinics, which, if they weren’t used for research, would probably just be destroyed

Against:

• Human embryos shouldn’t be used for experiments since each one is a potential human life

• Campaigners for the right of embryos feel that scientists should concentrate more on finding and developing other sources of stem cells, so people could be helped without having to use embryos.

Risks of stem cells

• can cause tumor’s

• organ damage

• the body might reject them

• infections

Explain the reasons for ethical and religious objections against stem cells

• Some think it’s wrong to play god by manipulating life

• Many religious people believe life starts at conception, so destroying embryos is killing life

Some conditions which may be helped by treatment with stem cells

• Blood Cancers - leukemia + lymphoma

• Neurological diseases - parkinson’s disease + Alzheimer’s disease + spinal cord injury

• Heart disease

• Eye conditions

• Diabetes

• Bone + joint issues

• Tissue damage

• Paralysis

What can stem cells from meristems in plants be used for

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically

• Rare species can be cloned to protect from extinction.

• Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.