Download Passing it on Notes

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The passing of traits from parents to their
offspring is called heredity.
The branch of science that deals with the
study of heredity is called genetics.
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Non-heritable traits: would not be passed
from one generation to another i.e.) playing a
musical instrument, environmental effects.
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For the most part organisms look like their
parent.
These characteristics are passed from parent
to offspring through sexual reproduction and
are called inherited or heritable traits
◦ Example: eye color, hair color, PTC paper, hands
crossed
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Traits are passed on through genetic material
YDNHTWTD
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Make a list of the traits listed on p38.
Get into partners and record for each person
which of the two forms of each trait each
person displays.
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Continuous variation: characteristics that
have a large range or continuum of
possibilities i.e.) height, hand span, eye color.
Discrete variation: characteristics that have a
limited number of possibilities(YES-NO
answers) i.e.) rolling your tongue, boy or girl,
blood type etc.
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Variation is passed on through chromosomes
Chromosomes – strings of genes, usually
found in pairs in body cells… (one from your
mom and one from your dad)
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Chromosomes are made up of genes…
Genes are sequences of DNA that code for
particular traits
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DNA: deoxyribonucleic acid p47
◦ a double helix structure of nucleic acids consisting of:
 phosphate
 Sugar
 nitrogenous bases called adenine, thymine, cytosine and
guanine
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Make it with marshmallows, fruit loops,
licorice…
Sugar
Phosphate group
Adenine bonds with
thymine
Guanine bonds with
cytosine
Nitrogenous bases
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Body cells have a complete set of chromosomes
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Body cells are found in every cell in your body!
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They are reproduced through mitosis.
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When cells divide uncontrollably, this is called
cancer or a tumour
◦ The daughter cell is an exact replica of the parent cell
◦ Same number of chromosomes (two pairs of each)
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Sex cells are your gametes ie. Sperm and
eggs
Gametes only have half of a complete set of
chromosomes for fertilization to create a
zygote.
They are produced through meiosis.
◦ The chromosomes are divided in half
◦ The daughter cells are not the exact same as the
parent cell
Sequences of DNA code for specific traits
 Each trait expressed by a gene (a sequence of
DNA) is represented by a single letter (ie.
blue eyes = b)
 Since you get one gene from your mom and
one gene from your dad, you will always have
two copies of each gene.
 Alleles – are different expressions of a trait
(ie. blue eyes vs. brown eyes) and are
represented by upper and lower case of the
same letter (B and b)
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Dominant Trait: the gene that is expressed,
even if there is only one. i.e.) “Tt” or “TT” you
will be able to roll your tongue
Recessive Trait: only when two genes are
inherited will the offspring show that trait.
i.e.) “tt” you will not be able to roll your
tongue
Not always will it be a dominant trait that
shows up in a population, sometimes it will
be a recessive trait that shows up most often.
Use traits from before…
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Homozygous is a genotype that has two of
the same “case” of letter ie. TT or tt
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Heterozygous is a genotype that has two
different cases ie. Tt
◦ Heterozyous is also called a carrier for the recessive
gene because it isn’t expressed
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You can use Punnett squares to determine
the:
◦ Probability of getting a particular trait or gene
◦ Possible combinations of genes from parents
1) Put the genes for the sperm on the
horizontal row and the egg on the vertical row.
2) Combine the genes to make the offspring in
each box using one from the sperm and one
from the egg.
3) Be sure to always put the capital letter first.
4) Then determine the trait that is expressed
5) If necessary, determine the probability.
Furry Family
Fill in the tables on the worksheet provided.
In humans, brown eyes (B) are dominant over
blue (b). A brown-eyed man marries a blueeyed woman and they have three children, two
of whom are brown-eyed and one of whom is
blue-eyed.
a)
Draw the Punnett square that illustrates
this marriage.
b)
What is the man’s genotype?
c)
What are the genotypes of the children?
In dogs, there is an hereditary deafness caused by
a recessive gene, “d.” A kennel owner has a male
dog that she wants to use for breeding purposes if
possible. The dog can hear, so the owner knows
his genotype is either DD or Dd. If the dog’s
genotype is Dd, the owner does not wish to use
him for breeding so that the deafness gene will not
be passed on. This can be tested by breeding the
dog to a deaf female (dd).
a)
Draw the Punnett squares to illustrate these
two possible crosses.
b)
In each case, what percentage/how many of the
offspring would be expected to be hearing?
deaf?
c)
How could you tell the genotype of this male
dog?
d)
Also, using Punnett square(s), show how two
hearing dogs could produce deaf offspring.
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Changes to DNA is called a mutation.
◦ Mutations cause changes in the structure of
organisms
◦ These changes can happen due to exposure to X
rays, ultraviolet rays, cosmic rays or chemicals.
◦ Mutagens cause mutations.
◦ Mutations can be beneficial, harmful or have not
affect on a person.
 Cancer is an example of a Mutation
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There are two ways that certain organisms
are selected to survive to pass on their genes
to the next generation
1) Natural Selection
 the idea is that the environment "selects" organisms
when only those organisms adapted to survive the
"best" can live long enough to reproduce
 "survival of the fittest" is based on competition
 Adaptations can happen in one generation or over
millions of years
 Always in a population
Bears of Banff
Bean Selection
Disperse or Disease
2) Artificial Selection : process of selecting
and breeding individuals with desirable
traits
 select parents to create hybrid
combination e.g.) beefalo, brociflower
 select parents with desirable traits already
Reproductive technology:
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Eg) artificial insemination: sperm from a male is
inserted into a female
Eg) in vitro fertilization: sperm and eggs are
mixed in a test tube and only the embryos with
desirable traits are selected
Eg) selective breeding: only use animals with
pedigrees
Eg) Genetic modification: bacteria making insulin
Eg) Genetic engineering
Eg) cloning
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Do you think animals should be tested for
possible genetic disorders?
Inbreeding depression
Species conservation? In the zoo,
reserves?
How many do we need to keep a gene
pool alive?
Captive breeding?
Zoos fund research?
Transgenic manipulation?
Cloning of rare animals?
Natural habitat of animals? (insanity)