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Unit A – Biological
Diversity
How do species have genetic variation?
Outcomes
7.
investigate the movement of characteristics from parents to
offspring, and identify examples of characteristics in offspring that
are:
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8.
the same as the characteristics of both parents
the same as the characteristics of one parent
intermediate between parent characteristics
different from both parents
distinguish those characteristics that are heritable from those that
are not heritable, and identify characteristics for which heredity
and environment may both play a role
9. identify examples of dominant and recessive characteristics
10. describe, in general terms, the relationship of chromosomes,
genes and DNA; and interpret their role as repositories of genetic
information
11. distinguish between cell division that leads to identical daughter
cells, as in binary fission and mitosis, and cell division that leads to
formation of sex cells, as in meiosis
DNA- Transmitter of Genetic
Code
• What is DNA?
• Also known as Deoxyribonucleic Acid
• The genetic material found in the nucleus of cells.
• It is the inherited material responsible for variation.
• Every single cell has DNA in its nucleus
• A nucleus is the “brain-center” of the cell and the DNA helps
to make the cell.
DNA and the Genetic Code
• James Watson and Francis Crick were the first to discover the
shape of DNA
• DNA looks similar to a twisted ladder- the sides of the ladder
are the same in all DNA molecules, but the rungs are what
makes the variation.
• Each rung is made up of a pair of chemicals called guanine,
cytosine, thymine, adenine.
• A always bonds with T
• G always bonds with C
The Genetic Code
• The arrangement of the four pairs can be read by cells and is
called the genetic code.
• All organisms have DNA from the same “instructions”
Edible DNA
• Ms. Deanne will demonstrate
• Materials: Licorice, Toothpicks, Coloured Marshmallows
Chromosomes
• Cells need lots of DNA to code for all the characteristics of an
organism
• If the DNA from a human cell was stretched out, it would be
about 2m long! More than 1 000 000 times the length of the
cell!
• DNA is packaged into smaller groupings called chromosomes.
• Each cell has 2 sets of chromosomes, for humans we receive
23 from our mom and 23 from our dad
Chromosomes
• Each organism has a different amount of chromosomes in a
complete set
• Humans complete set is 46 chromosomes
• Dogs a complete set is 78
• Most chromosomes are organized into pairs and therefore a
dog would have 39 pairs of chromosomes
• If a cat has 39 chromosomes in a complete set, how many
pairs of chromosomes would it have?
Genes
• A gene is a single uninterrupted segment of DNA, which
contains the coded instructions for the organisms
• Researchers found out by studying fruit flies that:
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Genes are located in the chromosomes
Each chromosome has numerous genes on it
Genes come in pairs like chromosomes
Both genes in a pair carry DNA instructions for the same thing ex.
Leg length
• Specific characteristic genes occupy matching locations on the
two chromosomes
• DNA code may not be exactly the same in both locations.
Genes
• Because the same gene on 2 pairs of chromosomes can have
different DNA and can give different results (blue eyes or
brown eyes)
• the different possible forms are called alleles.
To Do
• Draw this picture in your notes.
Allele
Cell Division
Review from last class
• What is a chromosome?
• What is a gene?
• What is an allele?
Cell Division and Asexual
Reproduction
• When a single-celled organism, as well as most cells in our
body divide, the cells contents are divided equally into 2
separate cells
• What does this mean about the DNA?
• Because both cells need the correct amount of DNA the
original cell doubles its DNA before splitting so that each cell
will receive the proper amount
• This process is called mitosis
Mitosis
Cell Division and Sexual
Reproduction
• If a male gamete and a female gamete both had regular
amounts of DNA, then when they combined there would be
twice as much as was needed.
• To solve this problem gamete cells undergo a process called
meiosis.
• Meiosis is a type of cell division where each cell ends up with
only half the DNA of a normal cell so when they combine the
zygote has a complete set of DNA
• Meiosis involves two cell divisions, not just one.
Meiosis
Drawing Mitosis and Meiosis
• Use figure 3.11 on page 47 to draw and label the steps of
mitosis and meiosis.
• This will be done in your notes.
• You also need to include in your own words what mitosis and
meiosis is.
• Do not quickly do this. Spend time on it making it detailed.
Patterns of Inheritance
• Long before research scientists discovered chromosomes and
genes, plant and animal breeders were conducting
experiments in controlled breeding.
• Phenotypes are characteristics physically seen
• Genotypes are traits that are found in genetics
Purebred
• Purebred is an animal or plant who ancestors have all had the
same form of trait. Also known as homozygous
• Example: Cats whose ancestors have only produced white
offspring for several generations.
• If we were to look at the alleles they would be the same.
• AA or aa
Hybrid
• An organism produced by crossing two individuals purebred
for different forms of a trait. Also know n as heterozygous
• Example: Breeding a purebred black cat with a purebred white
cat.
• If we were to look at the alleles they would be different
• Aa
Dominant Trait
• The outward form observed when two opposite-acting alleles
are inherited
• Example: Long leg length in fruit flies; an offspring with one
short leg allele and one long leg allele will grow long legs
because it is the dominant allele.
• Example: Black coat colour in cats. If you bred a white
purebred with a black pure bred they will always have a black
coat.
• Would these kittens be considered purebred or a hybrid?
• Recall that offspring of sexual reproduction inherit
genes from both parents.
• Both genes in a pair carry DNA instructions for the
same thing: coat colour.
• However the specific DNA instructions carried by the
alleles may not be identical (black or white)
Recessive Trait
• The outward form observed only when two same-acting, nondominant alleles are inherited.
• Example: Short leg length in fruit flies. An offspring with two
short leg alleles will grow short legs. There short-leg allele has
no influence if the dominant long leg allele is present
Incomplete Dominance
• Sometimes an allele is not completely dominant or recessive
and can show as a blend of traits.
• Example: A purebred red snapdragon breeds with a purebred
white snapdragon and their offspring will be pink
• Neither allele is truly dominant or recessive so both are
somewhat expressed.
Offspring Unlike Either Parent
• Sometimes offspring do not look like either parent or like a
mixture of the two
• Example: A black hair brown eyed father and a brown hair
brown eyed mother having a baby with red hair and blue eyes
• This can occur because inheritance might not be just as simple
as dominant or recessive traits.
• There may be many gene locations and several possible alleles
involved in certain characteristics.
• This is why it is possible to have one brown eye and one blue
eye
Punnett Square Example
Mendel’s Peas
• Scientist who
researched traits
with pea plants.
Recorded
observations in
plants
• This picture
looked at plant
height
Punnett Square Examples
Punnett Square Examples
Think about it!
• Does Environment have to do anything with phenotypes and
genotypes
Environmental Factors
• The action of genes is greatly influenced by the environment
in which an offspring develops.
• Example: FASD. If a mother drinks alcohol while pregnant it
can interfere with the normal development, even though the
DNA is still normal.
• Example: Many mothers in the 1950’s took the drug
thalidomide to help with morning sickness. One of it many
effects on the fetus was the abnormal development of limbs.
Many babies were born without their limbs. However when
they had children as adults their children were born normal.
Therefore the DNA was normal.