Download 1.2 DNA your genetic code

1.2 DNA: Your Genetic
Code
Nitrogenous Base  Codon  Gene 
DNA  Chromosome
Your future is in your “genes”
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
 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
How many chromosomes?
 Take a look at the difference in # of
chromosome pairs:
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



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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)
Karyotype
Chromosomes of a Human Male
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
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
 think AT the Golf Course
 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)