1. B5 Growth and Development
Revision Powerpoint

2. Cell Division Why do cells divide? Growth Reproduction
Replace damaged cells

3. Mitosis – making new body cells
Put the stages of mitosis in the correct order
Chromosomes separate and move to opposite ends of the cell
The cell grows and copies organelles
The cell has 2 copies of each chromosome and lots of mitochondria
The cell divides to make 2 identical cells
Answer:

4. Meiosis – making sex cells
gametes
Arrange the stages in order:
The original cell splits into 2
The 2 cells split into 4 daughter cells
The chromosomes copy
The chromosomes separate
The chromosomes separate again
Answer:

5. Compare mitosis and meiosis in human cells
Features
Mitosis
Meiosis
No. of chromosomes in mother cell 46
No. of daughter cells 2 4
No. of chromosomes in daughter cells 23
Used in
Asexual reproduction, growth and repair of cells
Making gametes

6. Fertilisation
Egg + sperm zygote
chromosomes

7. DNA and the Genetic Code
DNA is the molecule chromosomes are made of
The genetic code is the info needed to make a body
The genetic code is stored in your chromosomes
Each chromosome has many genes on it

8. The Double Helix A DNA molecule is 2 strands twisted together.
The bases always pair in the same way – this is base pairing
Adenine joins with Thymine
Guanine joins with Cytosine

9. Copying DNA Arrange in the correct order The 2 strands separate
The cell contains free bases which start to make new strands
The 2 new stands are identical to the original strands
Bonds between the bases split
G and C pair, A and T pair
Answer:

10. Making Proteins Proteins are made of a______ a_____ joined together.
Three bases code for 1 amino acid – this is the t_______ c_______
The gene on the DNA is copied by making m_____.
mRNA leaves the nucleus and goes to the r_________

11. How is DNA and mRNA different?
Single stranded
Double helix
Bases are A, U, G, C
Bases are A, T, G, C

12. Embryo Development
Up to the 8 cell embryo all cells are unspecialized embryonic stem cells
All the genes are switched on

13. Gene Switching Every nucleus contains all the genes
Some genes are switched off because they are not active
Eg amylase is only made in salivary cells and keratin is only made in hair cells

14. Stem Cell Technology (HT)
Scientists hope to treat diseases and replace damaged tissues with stem cells
Stem cells come from umbilical cord blood, early embryos and adults
Some people have ethical objections to using them
Tissues grown from embryonic stem cells have different gene to the person receiving the transplant and patients need drugs to stop rejection
Adult stem cells have most of their genes switched off and can only grow into a few cell types

15. Therapeutic Cloning Arrange the sentences!
The stem cells can develop into different organs and tissues.
The egg cell makes an embryo. Its genes are the same as the patients genes
Transplant the organ or tissue into a patient.
Take a nucleus out of a human egg cell. Replace it with a nucleus from a body cell of the patient.
After 5 days put the stem cells from the embryo in a dish of nutrients
Answers:

16. Growth and development in plants
Specialised cells are found in organs such as l_______, r______, s________ and f_________.
Some cells remain unspecialised – these are the m_________ cells found in the root and s______ tips and in rings around the stems and roots.

17. Phototropism – growth towards light
The hormone is called auxin

18. Cuttings Plant cuttings are clones of the parent plant.
Rooting powder contains auxin to encourage cell growth.