introduction to genetics genetics is all about dna genetics is all about dna dna is located in the...
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Introduction to Genetics
Genetics is all about DNA DNA is located in the nucleus of cells. The actual pieces of DNA are called
chromosomes. Chromosomes contain the genetic
code for everything (traits). Chromosomes are not visible until
they are ready to “divide/reproduce” In humans, 46 is the magic number.
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Reproduction
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Reproduction
Making new individuals from an existing individual
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How??
Chromosomes copy themselves and then “split” creating a new cell.
Methods:– Asexual (Mitosis)– Sexual (Meiosis)
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Asexual Reproduction
One parent Offspring (kids) are all identical to
parent and each other
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Method of Asexual Reproduction
Budding Fission Spores Vegetative Reproduction (runners)
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Budding
In this form, an offspring grows out of the body of the parent.
Hydras exhibit this type of reproduction.
Example: Potatoes
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Fission
The simplest form or reproduction and involves the division of a single organism into two complete organisms.
Each identical to the other and to the parent.
Common among unicellular organisms such as bacteria, many protist, some algae
(such as Spirogyra and Euglena), as well as a few higher organisms such as flatworms.
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Spores
Are DNA-containing capsules capable of sprouting into new organisms.
Spores are another form of asexual reproduction and are common among bacteria, protists, and fungi.
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Runners
Common among plants and consists of certain parts that grow out from a main parent plant and eventually root and sprout to form new, independent plants.
Examples: strawberry
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Mitosis In animals (humans) this form of
reproduction is used in “body cells.” Example : Skin cells must be
replenished Constant process The DNA of the cell copies itself and
then splits using a process called mitosis creating a new cell identical to the original
1 cell with 46 chromosomes – doubles (92) – splits into 2 cells with 46 chromosomes each (identical)
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Example of Mitosis:
Root Cells of a Broad Bean (Vicia faba)
In the "resting" phase the chromosomes are not obvious within the
nucleus.
Just before cell division starts, a lot of
metabolic activity occurs, the
chromosomes start to gradually shorten and
thicken.
Each chromosome has divided to
produce 2 identical chromatids, joined at a structure called the centromere.
They begin to move towards the equator
of the cell.
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Once at the equator of the cell, the
centromeres attach to threads of a spindle
structure that has formed. (The spindle
spans from one end of the cell to the other).
Contraction of the spindle fibers begins
to cause the chromatids to pull
apart from one another and move towards opposite ends of the cell.
The chromatids separate further. Energy for this is
provided by mitochondria.
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A new nuclear membrane begins to
form round the 2 groups of chromatids. A new cell wall begins
to be laid down.
The chromosomes begin to lengthen and
uncoil.
Two new cells, identical to each other and to the
parent cell. The cells now grow to full size.