1. 1.2 Genes: Answers and Questions
Nitrogenous Base  Codon  Gene 
DNA  Chromosome
Your future is in your “genes”

2. 1.2 Genes: Answers and Questions
(Page 16)
Chromosome – a thread-like structure made mostly of DNA, found in the nucleus of a cell
DNA (deoxyribonucleic acid) – material found in the cell nucleus that contains genetic information
Gene – a segment of DNA that controls protein production
Genome Management Information System, Oak Ridge National Laboratory
Copyright © 2010 McGraw-Hill Ryerson Ltd.

3. Chromosomes & DNA
The nucleus of almost every cell contains chromosomes
Chromosomes act like a master set of instructions that determine:
what each cell’s job is
how it will function
how long it will live before being replaced

4. Genes Direct Protein Production
(Page 17)
Genome Management Information System, Oak Ridge National Laboratory
Copyright © 2010 McGraw-Hill Ryerson Ltd.

5. Chromosomes Chromosomes come in pairs
every plant or animal species that reproduce sexually get 1 chromosome from their mother, 1 from their father
this means you are 50% your mom, 50% your dad
Depending on the species, there could be just a few pairs of chromosomes or many
humans have 23 pairs (46 chromosomes)
22 pairs, 1 pair of sex chromosomes
everyone’s chromosomes are a little different, which is why we are all different (except identical twins)
Chromosomes are composed of coiled strands of genetic information called DNA

6. Genes Direct Protein Production
(Page 17)
Copyright © 2010 McGraw-Hill Ryerson Ltd.

7. How many chromosomes?
Take a look at the difference in # of chromosome pairs:
human  23 pairs (46 chromosomes)
butterfly  190 pairs (380 chromosomes)
elephant  28 pairs (56 chromosomes)
ant  1 pair (2+ chromosomes)
tomato plant  12 pairs (24 chromosomes)
shark  41 pairs (82 chromosomes)
mosquito  3 pairs (6 chromosomes)

8. DNA Screening: Testing for Disorders
(Pages 19-20)
DNA Screening is the process of testing individuals to determine whether they have the gene or genes associated with a certain genetic disorders
PKU (phenylketonuria) – mutation in PAH gene
Down Syndrome – trisomy 21
Huntington Disease - mutation in HTT gene
Cystic Fibrosis – mutation in the CFTR gene
Edwards Syndrome – trisomy 18
Copyright © 2010 McGraw-Hill Ryerson Ltd.

9. Chromosomes of a Human Male
Karyotype

10. Down Syndrome – Trisomy 21

11. DNA (deoxyribonucleic acid)
The genetic material that acts like a master set of instructions for the organism
Coiled up strands of genetic information that make up a chromosome
Is divided into many genes that control protein production
gene = part of a DNA strand

12. The DNA Code
(Pages 17-18)
In 1953 scientists James Watson and Francis Crick created this model of DNA (the twisted ladder design is sometimes called a “double helix”).
Copyright © 2010 McGraw-Hill Ryerson Ltd.

13. DNA Made of nitrogen bases, ribose sugars, and phosphate backbones
these 3 parts all together are called a nucleotide
There are 4 nitrogen bases:
adenine
thymine
cytosine
guanine

14. 2 nitrogen bases always pair up:
adenine + thymine
cytosine + guanine
it’s in the gene sequence that we get differences among individuals
hair colour, how tall you are, what allergies you have, how quickly your fingernails grow, etc.

15. Codons: 3-letter words
the genetic code is like a book that only has words that are 3 letters long
the letters are nitrogen bases (nucleotides)
codons are 3-letter words that code for a certain protein to be made
ex: CAT, GAG, TAG, …
the sequence of codons decides which protein is produced
if there’s a mistake in the sequencing of a codon, we get what we know as a mutation
ex: CAT, GCG, TAG, …

16. Comparing Genetic Information to a Book
Book component
Biological equivalent
Letters
Words
Sentences
Paragraph
Chapters
Book
Nucleotides (nitrogen bases)
Codons
Genes
DNA
Chromosomes
Organism (human, butterfly, ant)

17. Altering Genes / Transgenic Organisms
(Pages 22-23)
Transgenic Organism – an organism whose genetic information has been altered with the insertion of genes from another species. These organisms are considered to be genetically modified organisms (GMOs).
Possible Uses For GMOs
Production of non-allergenic human proteins
Development of pest resistant crops
Increased growth of crops and livestock
Concerns
Spread of disease from GMOs
Negative effects on ecosystems
Allergic reactions from eating GMOs
Copyright © 2010 McGraw-Hill Ryerson Ltd.

18. Cloning
(Pages 24-25)
Cloning – the process of creating identical genetic copies of an organism
Pros and Cons of Cloning
Pro: Copies are made of “superior” animals. (increased milk & meat production)
Con: Clones may be less disease resistant
Copyright © 2010 McGraw-Hill Ryerson Ltd.

19. Mutations
( Pages )
Mutation – a change in the DNA of an organism; usual order of base pairs is altered which changes genes and effects the proteins produced. Not all mutations are harmful as they can occur in a non-genetic segments of DNA.
Mutagen – a substance or factor that can cause a mutation in DNA; DNA is physically damaged Examples: radiation (X-Rays, UV radiation), mercury, cigarette tar
UV mutated skin cells
sickle-shaped blood cells
albino American alligator
Copyright © 2010 McGraw-Hill Ryerson Ltd.

20. The Story of Dolly the Cloned Sheep
Retro Report | The New York Times
Video 13 min 39 s

21. Homework 
Page 18 # 1-3
Page 22 # 5-7
Page 28 # 1-4