growth & development

B5Growth &

Development

All living things are made up of cells.

Animal and Plant Cells

What else do we have to add?

Specialised cells……• cells in multicellular organisms can be

specialised to do particular jobs

Tissues and Organs• groups of specialised cells are called tissues

and groups of tissues form organs

Organisation

• Cells

• Tissues

• Organs

• Organ systems

• Organism

Plant Organs & Tissues

Zygotes

• a zygote is a fertilised egg• It has a set of chromosomes from each parent

Embryo

• a fertilised egg cell (zygote) divides by mitosis to form an embryo

Embryonic Stem Cells

•in a human embryo, up to the eight cell stage, all the cells are identical and could produce any sort of cell required by the organism,

(unspecialised cells or embryonic stem cells) •after this point, the cells become specialised and form different types of tissue;

Adult Stem cells• Adult stem cells remain unspecialised and can

become many, but not all, types of cell required by the organism

Mitosis

• Cell division by mitosis produces two new cells identical to each other and to the parent cell;

DNA

Cell CycleCell Growth : 1.numbers of organelles increase; 2. the chromosomes are copied when the two strands of eachDNA molecule separate and new strands form alongside them;

MitosisMitosis :

1. copies of the chromosomes separate

2. the nucleus divides

Meiosis (Makes Eggs In Ovaries, Sperm In S………?)

DNA

• DNA has a double helix structure;

http://www.statedclearly.com/what-is-dna/

Base Pairs

• both strands of the DNA molecule are made up of four different bases, which always pair up in the same way; A & T, C & G

Making Proteins

• the order of bases in a gene is the code for building up amino acids in the correct order to make a particular protein.

Genes code for Proteins

• The genetic code is in the nucleus but proteins are produced in the cell cytoplasm

• The genes (DNA) cannot leave the nucleus

So how does it happen?

A problem…….• You want to bake a chocolate cake• The recipe is in a cook book in the library• It’s a reference book – you can’t take it out of the library

Solution: Bring all the ingredients to the library and bake the cake there!

Protein synthesis

• Genes don’t leave the nucleus but…….

a copy of the gene is produced to carry the genetic code to the cytoplasm;

Switching genes off

• although body cells in an organism contain the same genes, many genes in a particular cell are not active because it only produces the specific proteins it needs;

Stem cells

• adult stem cells and embryonic stem cells have the potential to produce cells needed to replace damaged tissues

Ethics

• ethical decisions need to be taken when using embryonic stem cells

• this work is subject to Government regulation

Switching genes on again

• in carefully controlled conditions of mammalian cloning, it is possible to reactivate inactive genes in the nucleus of a body cell to form cells of all tissue types;

Plant Growth

• Unlike animals, most plants continue to grow throughout their lives

• • Plant meristems divide by mitosis to produce

cells that are unspecialised

Cuttings• These unspecialised new cells can specialise

into cells of xylem, phloem, roots, leaves or flowers;

• these unspecialised cells can be used to produce

clones of a plant with desirable

features, from cuttings;

Auxins

• cut stems from a plant can develop roots in the presence of plant hormones (auxins) and grow into a complete plant which is a clone of the parent;

Phototropism• understand how phototropism increases the

plant’s chance of survival; • phototropism in terms of the effect of light on

the distribution of auxin in a shoot tip.