Download 1.2 Genes: Answers and Questions

1.2 Genes:
Answers and Questions
Nitrogenous Base  Codon  Gene 
DNA  Chromosome
Your future is in your “genes”
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
http://genomics.energy.gov
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Chromosomes & DNA
 The nucleus of almost
every cell contains
chromosomes
 Chromosomes act like
a master set of
instructions that
determine:
1. what each cell’s job is
2. how it will function
3. how long it will live
before being replaced
Genes Direct Protein Production
Genome Management Information System, Oak Ridge National Laboratory
(Page 17)
http://genomics.energy.gov
Copyright © 2010 McGraw-Hill Ryerson Ltd.
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
Genes Direct Protein Production
http://genomics.energy.gov
(Page 17)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
How many chromosomes?
 Take a look at the difference in # of
chromosome pairs:
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


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)
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



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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.
Karyotype
Chromosomes of a Human Male
Down Syndrome –
Trisomy 21
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
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.
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
 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.
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, …
Comparing Genetic
Information to a Book
Book component
Letters
Biological equivalent
Nucleotides (nitrogen bases)
Words
Codons
Sentences
Genes
Paragraph
DNA
Chapters
Book
Chromosomes
Organism (human, butterfly, ant)
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.
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.
Mutations
( Pages 26-27 )
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.
The Story of Dolly the Cloned Sheep
Retro Report | The New York Times
https://www.youtube.com/watch?v=tELZEPcgKkE
Video 13 min 39 s
Homework 
Page 18 # 1-3
Page 22 # 5-7
Page 28 # 1-4