Biological Diversity Topic 5

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Transcript Biological Diversity Topic 5

When Plans Change
Topic 5
Review from last year
• You learned parts of the cell
• The control center is called…
• This control center contains….
Look familiar??
Now we get to look at that in much more detail!
DNA: The book of you - Joe Hanson
• http://www.youtube.com/watch?v=aeAL6xThf
L8&list=PL191A0CE65ECA0369
DNA
• Stands for deoxyribonucleic acid
• It is the inherited material responsible for
variation
• Found in all living things
• Found in the nucleus of each cell
• Needs to reproduce itself
• Must move from parent to offspring
• Controls all the structures and functions of
the cells.
DNA
Guanine and Cytosine will always fit together
Adenine and Thymine will always fit together
DNA includes nucleotides, each made of a phosphate, sugar
and nitrogen base.
DNA songs
• http://www.youtube.com/watch?v=ckZEds5ta
X4
•
http://www.youtube.com/watch?v=FUA6_Ucw3i4
More animations and Interactive sites
• http://www.youtube.com/watch?annotation_i
d=annotation_815353&feature=iv&src_vid=h
nSPGlpZx_Q&v=zwibgNGe4aY
• http://learn.genetics.utah.edu/content/begin/
tour/
Genetic Code
• The arrangement of these four bases form the
entire genetic code
• The backbone of the ladder is always the same
Sugar-phosphate-sugar-phosphate-sugar
• The structure is similar to a ladder that has been
twisted into a spiral – it is known as a double
helix
• James Watson and Francis Crick were the
scientists who discovered the structure of DNA
Building a DNA model
• Build A DNA model
On your completed DNA model,
label the following:
1. Sugar Phosphate backbone
2. Nitrogen Bases
3. NUCLEOTIDE (box around – sugar,
phosphate and one nitrogen base)
(text page 47)
Marking scheme for model:
• Complete (8 pairs in correct order)
• Coloured
• Labeled correctly
/10
/4
/6
TOTAL
/20
Chromosomes
• Are packages of DNA
• Each human cell nucleus has 46 chromosomes
(dogs have 78, cats have 38)
• Chromosomes are organized into pairs, humans
have 23 pairs.
• http://www.youtube.com/watch?v=bVk0twJYL6Y
&feature=related
• 18 Things You Should Know About Genetics
Genes
• Are a segment of DNA which
contains coded instructions
• Are located on chromosomes
• Each chromosome has many gene
locations
• Come in pairs
• Both genes in a pair carry the DNA
for the same trait (eye colour, leg
length)
• http://www.youtube.com/watch?v=
ubq4eu_TDFc&feature=related
• http://www.youtube.com/watch?v=
5MQdXjRPHmQ
http://www.ctvnews.ca/health/healthheadlines/ontario-to-start-screening-babiesfor-so-called-bubble-boy-disease-1.1418774
Alleles
• Are possible forms of a gene
• Organisms have two alleles for each trait.
• The arrangement of those alleles will determine
what trait will be expressed (shown).
– The gene for seed shape in pea plants exists in two
forms, one form or allele for round seed shape (R) and
the other for wrinkled seed shape (r).
– Example: A dog hair can be curly or straight, short or
long, coarse or fine, etc.
• Bill Nye
Genes
http://www.accesslearning.com/videodetail.cfm
?asset_guid=865D8FBB-025A-4185-A188DEA851EEAD93
Check and Reflect
(answer in Topic 5 notes booklet)
1.
2.
3.
4.
5.
6.
Define the term DNA in your own words and explain its function.
What four chemicals make up the genetic code? Describe how
these chemicals are arranged in a DNA molecule.
What is a chromosome? Describe its function.
What is an allele? Describe its function.
Explain why chromosomes are considered to be the “source of
diversity.”
Which of the following contains DNA?
a)
b)
c)
7.
Chromosome
Nucleus of a cell
Gene
If a chromosome was compared to a book, what would the words
of the book be compared to? Explain your answer.
Normal Cell Replacement
• The human body is incredibly complex and is
made up of many different kinds of body cells
– aka somatic cells.
• There are 60 trillion – 100 trillion somatic
cells in your body.
• Some last a lifetime, some last a few days.
• Chart on page 50 in your textbook.
Changing our Genetic Information
• Changes to the DNA are called mutations
• Causes (mutagens)
– X-rays
– Ultraviolet rays
– Cosmic rays
– Chemicals
• Results
– Cause changes in the structure of the DNA. The
individual bases could be mixed up.
Mutations
• Mutations in individual cells can cause cancer.
One mutated cell divides and creates a tumor.
That tumor could continue to spread.
• If a mutation happens in a sex cell, the
changes could be passed on from parent to
child.
• Mutations are not always negative, they are
sometimes beneficial, and often harmless.
Cell Division and Asexual Reproduction
http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf
http://www.youtube.com/watch?v=VlN7K1-9QB0
• Mitosis occurs in the body cells (for growth
and repair)
• Recall that when organisms divide through
binary fission, the two new organisms
created are identical.
• In order for them to be identical, they have
to have the same DNA.
• In order for this to happen, the parent must
double its DNA before it divides.
• In multicellular organisms, that production of
two new cells with the same number of
chromosomes is called MITOSIS
• http://www.bcscience.com/bc9/pgs/v_ani
mate_001_mitosis.html
Cell Division and Sexual Reproduction
in Plants and Animals
• Recall that in sexual reproduction, two gametes
join together to form a zygote
• Human body cells have 46 chromosomes, half
come from the mother’s gamete (23
chromosomes) and the other half from the
father’s gamete (23 chromosomes)
• MEIOSIS is the type of cell division that produces
gametes (sex cells) with only half the DNA of a
normal cell
• Meiosis involves two divisions.
http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf
Chromosomes from parents
Chromosomes
Duplicate
http://www.johnkyrk.com/meiosis.html
Chromosomes swap
some DNA
Try This
Organism
# of
chromosom
es in a cell
at the end
of mitosis
Cabbage
18
# of
chromosom
es in a body
cell
# of
chromosom
es in a
gamete
Black Bear
# of pairs of
chromosom
es
38
Human
Pear
# of
chromosom
es in a
zygote
23
40
Answers
Organism
# of
chromosom
es in a cell
at the end
of mitosis
# of
chromosom
es in a body
cell
# of
chromosom
es in a
gamete
# of
chromosom
es in a
zygote
# of pairs of
chromosom
es
Cabbage
18
18
9
18
9
Black Bear
76
76
38
76
38
Human
46
46
23
46
23
Pear
40
40
20
40
20
Complete the Online
Mitosis/Meiosis Animation Activity
http://www.learnalberta.ca/content/
secsu/html/biological_diversity/mito
sis/index.html
Review Questions
1. In way what is DNA a code?
2. Explain why the body cells of organisms that
reproduce sexually have even numbers of
chromosomes.
3. What is the main value of variation?
4. What form of reproduction favours variation?
Explain why by referring to DNA.
5. Is variation always an advantage? Explain.
Inheritance - terms
• Traits
– Characteristic of an organism
• Purebred
– Refers to a plant/animal that has ancestors with the same form
of a trait
• Hybrid
– Organism produced by crossing two individuals purebred for
two different traits
• Dominant Trait
– Cancels out any other trait. Ex. Black cat
• Recessive Trait
– Is cancelled out unless no dominant trait is present. Ex. White
cat
• Incomplete dominance
– Both traits are shown, neither is dominant or recessive
Offspring Unlike Either Parent
• Explain why some traits like hair colour, eye
colour, and skin colour cannot always be
explained by just looking at the parent.
• There are many gene locations and several
possible alleles involved
Environmental Factors
• Can genes be influenced by the environment?
Give an example.
• Yes, workers who work with really strong
chemicals can end up with mutated cells if proper
precautions aren’t taken.
• Yes, alcohol in a pregnant woman’s bloodstream
interferes with brain development and facial
features of the baby (even though DNA is normal)
Give it a Try answers
In fruit flies inherits two possible alleles for leg
length: long-leg and short-leg
ANSWERS
• Long legs
• Short legs
• Can’t say for sure, does not state which is
dominant
Give it a Try answers contd
In fruit flies, there are two possible alleles for
eye colour: red-eye and purple eye
ANSWERS
• RR RP PP
• Dominance not known
Give it a Try answers contd
In fruit flies, there are two possible alleles for
wing shape: long-wing and dumpy-wing
ANSWERS
• LL LD DD
• Dominance not known
Give it a Try answers contd
An individual fruit fly might have long legs, purple
eyes and long wings (LPW). What other
combinations of leg length, eye colour, and wing
shape are possible?
LRW
LRD
SRW
SRD
LPD
SPD
LPW
SPW
Review Questions
1. How could two black cats produce a kitten that has
white fur? Use a diagram to explain your answer.
2. If you wanted to be certain that a trait would appear
in the offspring of the plants or animals that you were
breeding, what would you have to find out about the
parents? Explain your answer.
3. Suppose a new flower in your garden displays
intermediate colour. For example, you begin to see
orange flowers although you originally planted only
red and yellow flowers. What pattern of inheritance
would you be observing in this situation? Explain your
answer.