Download Practical Genetics

Practical Genetics
By dr. Rehab Mamdouh
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Blood grouping
1. The differences in human blood are due to the presence or absence of certain
protein molecules called antigens and antibodies.
2. The antigens are located on the surface of the red blood cells and the
antibodies are in the blood plasma. Individuals have different types and
combinations of these molecules.
Significance of the blood grouping:
For a blood transfusion to be successful blood groups must be compatible between the
donor blood and the patient blood. If they are not, the red blood cells from the donated
blood will clump or agglutinate. The agglutinated red cells can clog blood vessels and
stop the circulation of the blood to various parts of the body. The agglutinated red
blood cells also crack and its contents leak out in the body. The red blood cells
contain hemoglobin which becomes toxic when outside the cell. This can have fatal
consequences for the patient.
What are the different blood groups?
There are more than 20 genetically determined blood group systems known, but the
AB0 and Rh systems are the most important ones used for blood transfusions.
(A) AB0 blood grouping system:
According to the AB0 blood group system there are four different kinds of blood
groups:
1. Blood group A:
If you belong to the blood group A, you have A antigens on the surface of your red
blood cells and B antibodies in your blood plasma.
2. Blood group B:
If you belong to the blood group B, you have B antigens on the surface of your red
blood cells and A antibodies in your blood plasma.
3. Blood group AB:
If you belong to the blood group AB, you have both A and B antigens on the surface
of your red blood cells and no A or B antibodies at all in your blood plasma.
4. Blood group 0:
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If you belong to the blood group 0 (null), you have neither A or B antigens on the
surface of your red blood cells but you have both A and B antibodies in your blood
plasma
(B) Rh (Rhesus) factor blood grouping system:
1. Rh+
Many people also have a so called Rh factor on the red blood cell's surface. This is
also an antigen and those who have it are called Rh.+
2. RhThose who haven't Rh factor on the red blood cell's surface are called Rh-.
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Observing Mitosis with Fluorescence Microscopy in onion root tips Showing different
stages (prophase, Metaphase, anaphase, telophase and cytokinesis
Comment:
Mitosis is the mechanism that allows the nuclei of cells to split and provide each daughter cell
with a complete set of chromosomes during cellular division. This, coupled with cytokinesis
(division of the cytoplasm), occurs in all multicellular plants and animals to permit growth of
the organism.
Interphase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
normal resting cell exists in a state called interphase in which the chromatin is
undifferentiated in the heavily-stained nucleus, as illustrated above. Before the cell enters the
mitosis phase, it first undergoes a synthesis or S phase where each chromosome is
duplicated and consists of two sister chromatids joined together by a specific DNA sequence
known as a centromere.
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Early prophase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
The first phase of mitosis is known as the prophase, where the nuclear chromatin starts to
become organized and condenses into thick strands that eventually become chromosomes.
During prophase, the cytoskeleton (composed of cytoplasmic microtubules) begins to
disassemble and the main component of the mitotic apparatus, the mitotic spindle begins to
form outside the nucleus at opposite ends of the cell. The photomicrograph below depicts the
initial chromosome condensation at the beginning of prophase (early prophase) when the
nucleolus is still intact.
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Late prophase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
Late prophase begins with the disruption of the nuclear envelope, which is broken down into
small membrane vesicles that closely resemble the endoplasmic reticulum and tend to remain
visible around the mitotic spindle. During this period the chromosomes continue to condense
and gradually shorten and thicken until they have completely formed the units that will
undergo mitosis. The nucleolus also disappears during this period. The mitotic spindle
microtubules are now free to enter the nuclear region, and formation of specialized protein
complexes called kinetochores begins on each centromere. These complexes become
attached to some of the spindle microtubules, which are then termed kinetochore
microtubules. Other microtubules in the spindle (not attached to centromeres) are termed
polar microtubules and these help form and maintain the spindle structure along with astral
microtubules, which remain outside the spindle.
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Metaphase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
The current phase is called metaphase where the chromosomes, attached to the kinetochore
microtubules, begin to align in one plane (the metaphase plate) halfway between the spindle
poles. The kinetochore microtubules exert tension on the chromosomes and the entire
spindle-chromosome complex is now ready for the next event.
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Early Anaphase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
Almost immediately after the metaphase chromosomes are aligned at the metaphase plate,
the two halves of each chromosome are pulled apart by the spindle apparatus and migrate to
the opposite spindle poles. The kinetochore microtubules shorten as the chromosomes are
pulled toward the poles, while the polar microtubules elongate to assist in the separation. The
photomicrograph below illustrates the early stage of anaphase where the chromosomes are
just becoming completely separated. The microtubules are clearly visible in this complex.
q
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Late Anaphase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
Anaphase typically is a rapid process that lasts only a few minutes. When the chromosomes
have completely migrated to the spindle poles, the kinetochore microtubules begin to
disappear, although the polar microtubules continue to elongate.
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Telophase was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
chromosomes and their extrusion to the spindle poles, the nuclear membrane begins to
reform around each group of chromosomes at the opposite ends of the cell. The nucleoli also
reappear in what will eventually become the two new cell nuclei. The photomicrograph below
captures a cell in late telophase where the new membrane is beginning to divide the cell but
the nuclei have not completely reformed and cytokinesis has not yet finished.
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Cytokinesis was Observed with Fluorescence Microscopy in onion root tips
Division type: Mitosis
Comment
When telophase is complete and the new cell membrane (or wall in the case of the onion root
tips) is being formed, the nuclei have almost matured to the pre-mitotic state. The final steps
are completion of the total formation of a membrane between each of the new daughter cells
to yield two separate new cells.
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Give the crossing probability for first and second
generation of two traits between purpled flower's plant
which has tall stem. You should Know these traits are
dominant.
d TRUEBREEDING
purple
white
flowers, tall
flowers,
dwarf
PARENTS:
AABB
GAMETES:
AB
x
AB
ab
F1 HYBRID
AaBb
OFFSPRING:
All purple-flowered, tall
16 Allele Combinations in F2
9: purple flowers and tall
3: purple flowers and dwarf
3: white flowers and tall
1 white flowers and dwarf
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aabb
ab
gametes AB
Ab
aB
ab
AB
AABB
AABb
AaBB
AaBb
Ab
AABb
AAbb
AaBb
Aabb
aB
AaBB
aABb
aaBB
aaBb
ab
AaBb
Aabb
aaBb
aabb
Give an example for incomplete dominance?
e.g: Flower Color in Snapdragons
Red-flowered plant
X
(homozygote)
White-flowered plant
(homozygote)
Pink-flowered F1 plants
Heterozygotes
Pink-flowered plant
X
Pink-flowered plant
White-, pink-, and red-flowered plants
in a 1:2:1 ratio
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