dna and it’s replication - flippedoutscience.com...dna structure dna consists of two molecules...
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DNA AND IT’S
REPLICATION• What is DNA, and how does it make more of
itself?
• How does DNA get passed on to the next
generation?
7.14B compare the results of uniform or diverse offspring from sexual
reproduction or asexual reproduction
7.14C recognize that inherited traits of individuals are governed in the
genetic material found in the genes within chromosomes in the nucleus
DNA Structure
DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.
A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
Each nucleotide consists of:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base
Nucleotides – look like this:
Phosphate
Pentose
Sugar
Nitrogenous
Base
Draw this!
Nucleotides
The phosphate and sugar
form the backbone of the DNA molecule, whereas the
bases form the “rungs”.
There are four types of nitrogenous bases.
Phosphate
Sugar
bases
4 Types of Nucleotides
A
Adenine
T
Thymine
G
Guanine
C
Cytosine
Nucleotides
Each base will only bond with one other specific
base.
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Form a base pair.
Form a base pair.
G
G
A
T
T
A
A
C
T
G
C
A
T
C
First they pair up,
Then the bonding
occurs.
This is what
makes the ladder
formation!
DNA
Structure
Because of this
complementary
base pairing, the
order of the bases
in one strand
determines the
order of the bases
in the other strand.
DNA Structure
You learned before that a gene is the part of your DNA that influences a trait. It is also a section of DNA that codes for a protein.
Each unique gene has a unique sequence of bases.
This unique sequence of bases will code for the production of a unique protein.
It is these proteins and combination of proteins that give us a unique phenotypes.
Recall that Phenotypes are…
all the observable characteristics of an organism,
such as shape, size, color of eyes and hair
This is how DNA = YOU!
Who discovered the model of DNA?
In 1953, Frances Crick and James Watson modeled the chemical structure of DNA.
The order of four molecules codes for every part and kind of life.
Life is incredibly diverse!
Where is the DNA?
In each cell, there is a nucleus (in eukaryotic cells)
And in the nucleus is the genetic material, the DNA
DNA is too long to fit into that tiny cell; if you were to string out one cell’s DNA, it would be 6 feet long.
So, chromosomes “package” the DNA so it fits!
How DNA is packaged (1 min.)
How does DNA replicate?
The two strands of DNA must be separated and
copied.
One protein separates the two strands of DNA.
Another protein brings the correct new base to pair
with the existing base, matching them.
DNA Replication
In this way, two DNA
strands are formed from
one (the first one is copied).
Each new DNA double
helix has one old strand
(the parent strand) and
one new strand (the
daughter strand).
Daughter Strand
Daughter
Strand
Parent
Strands
Your DNA
All of the DNA in a cell of a human is called the
“human genome”.
The human genome has over 3.2 billion base
pairs.
Humans have 23 pairs of chromosomes
DNA - Videos
https://www.youtube.com/watch?v=zwibgNGe4aY
https://www.youtube.com/watch?v=5qSrmeiWsuc
https://www.youtube.com/watch?v=zdDkiRw1PdU
(short)
TYPES OF
REPRODUCTIONAsexual Reproduction
Sexual Reproduction
Purpose of Reproduction
To make sure a species can continue
To make new cells
Asexual Reproduction
New organism is produced from ONE parent
Offspring are IDENTICAL to the parent and
each other.
Genetic material is donated from that one
parent. (so is there variety in the genes?)
Very common in plants; less so in animals
Examples of Asexual Reproduction
Budding – living organisms make
offspring that form from
outgrowths (buds) on the bodies of
the parent.
some organisms like hydra and
corral can form a mass of cells
called a “bud”.
That bud specializes to form a new
organism on the side of the parent.
It will drop off and become its own
organism.
Examples of Asexual Reproduction
Vegetative propagation – some plants can grow whole
new plants from divided parts
It will drop off and become its own organism.
Ex. spider plant
Examples of Asexual Reproduction
Spores – seed like capsules of DNA
and tissue that can grow under the
right conditions.
They are produced by nonflowering
plants, bacteria, fungi, and algae, and
are often able to travel over long
distances.
Ex. mushrooms, molds
Examples of Asexual Reproduction
Regeneration –some organisms (starfish and the salamander) can replace an injured or lost part, and many plants are capable of total regeneration (the formation of a whole individual from a single fragment such as a stem, root, or leaf)
Examples of Asexual Reproduction
Binary Fission -
The process in
which a parent
cell splits into
two daughter
cells of
approximately
equal size.
Advantages and Disadvantages
Asexual Reproduction
Advantages:
o Faster and easier – no partner needed
o Less chance of mutation – less steps to follow,
so less chance things can go wrong
• Disadvantages:
o Less genetic diversity (parents = to
offspring) means less chance of survival if
the environment changes
Sexual Reproduction
Sexual Reproduction - the production of new living organisms by combining genetic information from two individuals of different types (sexes).
Genetic material is donated from two parents
The process is called fertilization
Half of the genes for each trait come from the male parent and half from the female parent.
Offspring differ from each parent and from each other.
Parents typically care for their offspring.
There are less offspring (in general)
Examples of Sexual Reproduction
Pollination - Plants that rely on flowers for reproduction
are also very dependent on outside help such as insects
and animals.
A bee might go to one flower and get a little pollen on
its back. If it goes to another flower of the same
species, that pollen can land on the stigma. If
successful, an embryo and seed/fruit develop
respectively.
https://www.youtube.com/watch?v=1OFF2qYvLag
Sexual Reproduction examples:
Sexual reproduction in animals
Animal male gamete is called sperm. Sperm is a
mobile cell that moves using its 'tail', called
flagellum. Female gamete is called an ovum. It
does not move and it is much larger than sperm
The egg and sperm combine for fertilization.
Advantages and Disadvantages of
Sexual Reproduction
Advantages:
Greater genetic diversity due to large number of gene combinations that can occur (think increased biodiversity)
Disadvantages:
It is a slow process, and a greater chance of mutations in the DNA replication process
Energy is expended finding a mate
Only works in complex organisms
Important !!!!!!!!!!!
Asexual reproduction results in offspring
that are genetically identical to the
parent organism
Sexual reproduction results in offspring
that are genetically different from the
parent organisms
Your notes should be complete!
Check them for completion and then place them in
your binder.