science 9 - biodiversity. what is dna and where do we find it? each person’s dna is very different...
TRANSCRIPT
Topic 5 – When Plans Change (DNA)
Science 9 - Biodiversity
What is DNA and where do we find it?Each person’s DNA is very different from
others.DNA:Deoxyribonucleic acidComposed of genetic material (inherited
material)Responsible for variationControls the formation of cellsFound in the nucleus of the cell
Watson & Crick figured out that DNA was organized as a double helix
Make-Up of DNA4 chemicals called nitrogen bases (rungs of
the ladder)Guanine – GCytosine – CAdenine – A Thymine – T
Alternating sugar & phosphates (sides of the ladder)
To do:Discovery Streaming Videos – DNA intro &
Genetic Engineering
When you place ATCG into various orders, you can create thousands of different combinations – called genetic code (codes for what we will be like)
One cell contains about 2 m of DNAHow does it all fit into one cell?
The DNA wraps into chromosomes
ChromosomesEach human has 23
pairs of chromosomes (46)
Different species have different numbers of chromosomes
Contain numerous genes
Are inherited from our parents
GenesUninterrupted segment
of DNA which contain coded instructions
Are found on the chromosome
Come in pairs (one from each parent)
Both pairs carry DNA for the same thing Ex: leg length
Different “flavours” of genes are called alleles
Alleles: a possible form of a geneEx: blue or brown
eyes (B or b)
Answer in your notes…In what ways is DNA a code?
Remember…Chromosome = cookbookGene = recipeBase pairs (ATCG) = words
Topic 5Mitosis and Meiosis
Quick Review:What are the 4 base pairs?
Thymine, adenine, guanine, cytosine
What pairs are joined together?AT and CG
What is the outside of the double helix made out of?Phosphates and sugars
How do we grow?Cells divide and multiply in order to grow!
There are 2 different ways in which we go about this:
1. Mitosis (creates all body cells)2. Meiosis (creates reproductive cells)
MITOSIS Draw picture – then add in stepsMitosis has 4 steps:1. DNA replicates (doubles)2. Chromosomes line up along midline3. Chromosomes split to the 2 sides of the cell4. Cleavage occurs
Produces 2 body cells (somatic cells) with the same
number of chromosomes as the parent cell These are DIPLOID CELLS (2n)
Examples of mitosis
Meiosis Draw picture – then add in stepsMeiosis has 8 steps:1. DNA replicates2. Chromosome pairs line up at midline3. Crossover can occur(creates variation)4. Chromosomes split to 2 sides of cell5. Split #16. Chomosomes line up at midline7. Chromosomes split to 2 sides of cell8. Cleavage
Produces 4 sex cells that have half the number of chromosomes as the parent cell
MEIOSISOn what type of cells does meiosis occur?
Egg cellSperm cell
THESE are called HAPLOID CELLS (n)
Think about it…An organism has five pairs of chromosomes.
One of the organism’s body cells divides. How many cells are formed? How many chromosomes does each new cell have?
How many chromosomes would be in each sperm cell?
Why do the body cells of all organisms that reproduce sexually have even numbers of chromosomes?
The Benefits of VariationWhat is a benefit of asexual reproduction?
What is a benefit of sexual reproduction?
Which type of reproduction is better for offspring survival?
What does variation mean?
Technology and VariationRead pg. 53-54Define:
Genetic engineeringBiotechnologiesTransgenicAquaculture
Make notes that are 2-3 points on the following 3 titles:Biotechnology in MedicineBiotechnology in Food ProductionA Cost-effective Crop
“Modelling DNA” activity