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DNA
• DNA is the molecule that is in charge of
storing genetic information.
DNA
• DNA is the molecule that is in charge of
storing genetic information.
• It’s like the English language except that
there are only 4 letters (A,T,C,G) and all
the words are 3 letters long.
DNA
• DNA is the molecule that is in charge of
storing genetic information.
• It’s like the English language except that
there are only 4 letters (A,T,C,G) and all
the words are 3 letters long.
• A single section of DNA would contain
those letters (nucleotides) in some
sequence. If this section is in ‘charge’ of
something we call it a gene……
GENE
• Gene – a section of DNA in charge of
something.
GENE
• Gene – a section of DNA in charge of
something.
• Could be in charge of making a protein
(like the gene for the molecule keratin has
its nucleotides in an order such that the
amino acid sequence that is made from
those directions will make keratin)
GENE
• Gene – a section of DNA in charge of
something.
• Could be in charge of making a protein (like the
gene for the molecule keratin has its nucleotides
in an order such that the amino acid sequence
that is made from those directions will make
keratin)
• Could be a ‘regulatory’ gene – like a foreman in
a factory who produces nothing directly, but who
receives directions and then directs others to
influence what gets made. Easier to think of the
former – one gene, one protein.
CHROMOSOMES
• The total DNA of an organism (its genome)
is small enough in bacteria that it can all
be on a single molecule. It’s a single
circular chromosome.
CHROMOSOMES
• The total DNA of an organism (its genome)
is small enough in bacteria that it can all
be on a single molecule. It’s a single
circular chromosome.
• But in us complex creatures, there’s way
too much to fit on one chromosome. So
it’s packaged in ‘volumes’.
CHROMOSOMES
• The total DNA of an organism (its genome) is
small enough in bacteria that it can all be on a
single molecule. It’s a single circular
chromosome.
• But in us complex creatures, there’s way too
much to fit on one chromosome. So it’s
packaged in ‘volumes’.
• Every organism has a ‘characteristic’ # of
chromosomes. Fruit flies have 8. Plants have
many dozens, even hundreds. We humans have
46.
SOOOOO…
• A chromosome consists of a long stretch
of DNA, portions of which are ‘genes’. So,
we could say that a chromosome consists
of a bunch of genes.
SOOOOO…
• A chromosome consists of a long stretch of
DNA, portions of which are ‘genes’. So, we
could say that each chromosome consists of a
bunch of genes.
• These genes are NOT organized by function.
For example, there is a set of genes that
collectively are in charge of cell division. But
they aren’t located together – they’re spread out
amongst all the chromosomes.
ALSO!
• Remember that each of us complex
critters have a set of genetic material from
mom and another from dad.
• Remember that each of us complex
critters have a set of genetic material from
mom and another from dad.
• So you have a pair of each of 23
chromosomes
• Remember that each of us complex
critters have a set of genetic material from
mom and another from dad.
• So you have a pair of each of 23
chromosomes
• Each pair is homologous in that they have
the same genes – they’re in charge of the
same stuff.
GENE RELATIONSHIPS
• What this means is that the homologous
genes might not say the same thing for
example, the earlobe gene might say
‘attached’ or might say ‘free’.
GENE RELATIONSHIPS
• What this means is that the homologous
genes might not say the same thing for
example, the earlobe gene might say
‘attached’ or might say ‘free’.
• If they do say the same thing there’s no
argument between the genes. This is
‘homozygous’.
GENE RELATIONSHIPS
• But if they’re different they’ll need to find
way to resolve that difference.
GENE RELATIONSHIPS
• But if they’re different they’ll need to find
way to resolve that difference.
• A different form for a particular gene is
called an ‘allele’.
GENE RELATIONSHIPS
• But if they’re different they’ll need to find
way to resolve that difference.
• A different form for a particular gene is
called an ‘allele’.
• Mendel’s pea plant alleles all had a
particular kind of relationship.
GENE RELATIONSHIPS
• But if they’re different they’ll need to find
way to resolve that difference.
• A different form for a particular gene is
called an ‘allele’.
• Mendel’s pea plant alleles all had a
particular kind of relationship.
GENE RELATIONSHIPS
• If they were both present (one from mom,
one from dad, called ‘heterozygous’) only
one was ‘expressed’.
OTHER VOCABULARY
• Trait – a physical characteristic
OTHER VOCABULARY
• Trait – a physical characteristic
• Genotype – the actual genetic makeup of
the organism (homozygous dominant,
heterozygous, homozygous recessive) for
a particular trait
OTHER VOCABULARY
• Trait – a physical characteristic
• Genotype – the actual genetic makeup of
the organism (homozygous dominant,
heterozygous, homozygous recessive) for
a particular trait
• Phenotype – what it looks like – for that
trait.
OTHER VOCABULARY
• Trait – a physical characteristic
• Genotype – the actual genetic makeup of
the organism (homozygous dominant,
heterozygous, homozygous recessive) for
a particular trait
• Phenotype – what it looks like – for that
trait.
• Locus – where the gene is located
OTHER VOCABULARY
• Gamete – a sperm or egg – has one set of
chromosomes.
OTHER VOCABULARY
• Gamete – a sperm or egg – has one set of
chromosomes.
• Haploid – refers to any cell with only one
set of chromosomes – like gametes!
OTHER VOCABULARY
• Gamete – a sperm or egg – has one set of
chromosomes.
• Haploid – refers to any cell with only one
set of chromosomes – like gametes!
• Zygote – the product of two gametes
coming together in fertilization
OTHER VOCABULARY
• Gamete – a sperm or egg – has one set of
chromosomes.
• Haploid – refers to any cell with only one
set of chromosomes – like gametes!
• Zygote – the product of two gametes
coming together in fertilization
• Diploid – any cell with two sets of
chromosomes – most of our cells are