1.2 Cell Division

• The nucleus of a cell contains chromosomes made of ________ molecules.

• Each chromosome carries a large number of ________.

• In body cells the chromosomes are normally found in ________.

• DNA

• genes

• pairs

Cells divide in a series of stages called the ______ ________.

cell cycle

Describe the stages of the cell cycle.

• During cell cycle — genetic material is doubled → divided into 2 identical cells

• Before a cell divides it grows and increases number of sub-cellular structures

  • DNA replicates → forms 2 copies of each chromosome

• Mitosis — 1 set of chromosomes pulled to each end of cell and nucleus divides

• Cytoplasm and cell membranes divide → forms 2 identical cells

Why is cell division by mitosis important?

For growth and development of multicellular organisms

What is a stem cell?

Undifferentiated cell — can divide to produce many specialised cells of same type

What are the three types of stem cells?

• Embryonic stem cells

• Adult stem cells

• Meristems — plants

When do embryonic stem cells form?

Egg and sperm fuse → forms zygote

Embryonic stem cells can be __________ and _________________ into any type of cell in the body.

• cloned

• differentiate

What are some uses of embryonic stem cells?

• Grow new tissues and organs

• Treat medical conditions:

  • paralysis

  • diabetes

Adult stem cells found in ________ _________ can be used to form many types of cells — including _______ ________.

• bone marrow

• blood cells

Where are meristems found in plants?

Root and shoot tips

Meristem tissue in plants can ____________ into any type of plant cell, throughout the life of the plant.

differentiate

What happens in therapeutic cloning?

Embryo produced with same genes as patient

Why can embryos produced from therapeutic cloning be used for medical treatment?

Stem cells from embryo have same genes → not rejected by patient’s body

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

What are two examples of this?

• Rare species cloned → protection from extinction

• Crop plants with desirable features (e.g. disease resistance) cloned → produced large numbers of identical plants

What are the advantages and disadvantages of research with stem cells?

• Replace damaged/diseased body parts

• Unwanted embryos can be used — not discarded

• Research into differentiation

• Transfer of viral infection

• Ethical/religious objections