Guidelines biomole col. 2 Actual Final Exam
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Motor proteins convert ATP energy into mechanical movement along
cytoskeletal tracks.
Dynein (minus-end directed):
Pulls chromosomes toward centrosomes and helps focus spindle poles.
Myosin (actin-based):
Forms the contractile ring during cytokinesis, creating the cleavage
furrow that divides the cell.
motor proteins in cell division
,Somatic mosaicism occurs when an individual has two or more
genetically distinct cell populations that arise from a mutation after
fertilization.
Formation mechanism: Caused by errors during early mitotic divisions
of the zygote, such as mitotic nondisjunction or other chromosomal
mutations.
Trisomic rescue: A trisomic zygote (three copies of a chromosome) may
lose one chromosome during division, producing a mixture of trisomic
and normal (disomic) cells.
Clinical example: In Down syndrome (Trisomy 21), mosaicism occurs in
about 2–4% of cases, leading to both normal and trisomy 21 cell lines in
the same individual.
explain formation of somatic mosaicism
Germline mosaicism occurs when an individual has genetically
different cell populations specifically in their germ cells (sperm or
egg-producing cells).
Key feature: The mutation is present only in some germ cells, while the
person’s body (somatic cells) is usually unaffected.
Clinical significance: The individual typically shows no symptoms, but
can still pass the mutation to offspring if affected gametes are involved.
Inheritance pattern impact: It can explain why a genetic disorder
appears in multiple siblings despite unaffected parents.
explain formation of germ line mosaicism
,Mitochondrial mosaicism happens when different cells in the same
person have different types or amounts of mitochondrial DNA.
High mutation rate: Mitochondrial DNA changes (mutates) more often
than nuclear DNA, so cells can end up with both normal and mutated
mitochondria.
Random distribution: When cells divide, mitochondria are shared
randomly between daughter cells.
Uneven mix: This creates cells with different proportions of normal and
mutated mitochondria.
Disease threshold: Some cells may have enough mutated
mitochondria to cause disease, while others do not, leading to a
mosaic pattern of symptoms in the body.
explain formation of mitochondrial mosaicism
, Nondisjunction is the failure of chromosomes or sister chromatids to
separate properly.
* Meiosis I errors: Failure of homologous recombination or chiasma
formation prevents correct pairing, so homologous chromosomes do
not separate.
* Meiosis II errors / mitosis errors: Failure of sister chromatid separation
due to spindle or cohesion defects.
Molecular causes:
* Recombination defects: improper DNA break repair → weak or absent
chiasmata
* Checkpoint failure (Aurora kinases, Plks): incorrect spindle formation
or attachment is not corrected
* Motor protein failure (kinesin/dynein): chromosomes are not pulled
apart correctly
* Cohesin breakdown errors: sister chromatids stay stuck together too
long or separate too early
➡ Result: gametes with extra or missing chromosomes, leading to
trisomy or monosomy after fertilization
describe how errors in somatic and germ cell division can lead to
trisomy or monosomy and cause human pathology
2026-2027 Newest Exam Version With
Complete Accurate Real Exam Questions
With Elaborated Answers And Rationales
Verified 100% || Guaranteed Pass A+
||Brand New!!
Motor proteins convert ATP energy into mechanical movement along
cytoskeletal tracks.
Dynein (minus-end directed):
Pulls chromosomes toward centrosomes and helps focus spindle poles.
Myosin (actin-based):
Forms the contractile ring during cytokinesis, creating the cleavage
furrow that divides the cell.
motor proteins in cell division
,Somatic mosaicism occurs when an individual has two or more
genetically distinct cell populations that arise from a mutation after
fertilization.
Formation mechanism: Caused by errors during early mitotic divisions
of the zygote, such as mitotic nondisjunction or other chromosomal
mutations.
Trisomic rescue: A trisomic zygote (three copies of a chromosome) may
lose one chromosome during division, producing a mixture of trisomic
and normal (disomic) cells.
Clinical example: In Down syndrome (Trisomy 21), mosaicism occurs in
about 2–4% of cases, leading to both normal and trisomy 21 cell lines in
the same individual.
explain formation of somatic mosaicism
Germline mosaicism occurs when an individual has genetically
different cell populations specifically in their germ cells (sperm or
egg-producing cells).
Key feature: The mutation is present only in some germ cells, while the
person’s body (somatic cells) is usually unaffected.
Clinical significance: The individual typically shows no symptoms, but
can still pass the mutation to offspring if affected gametes are involved.
Inheritance pattern impact: It can explain why a genetic disorder
appears in multiple siblings despite unaffected parents.
explain formation of germ line mosaicism
,Mitochondrial mosaicism happens when different cells in the same
person have different types or amounts of mitochondrial DNA.
High mutation rate: Mitochondrial DNA changes (mutates) more often
than nuclear DNA, so cells can end up with both normal and mutated
mitochondria.
Random distribution: When cells divide, mitochondria are shared
randomly between daughter cells.
Uneven mix: This creates cells with different proportions of normal and
mutated mitochondria.
Disease threshold: Some cells may have enough mutated
mitochondria to cause disease, while others do not, leading to a
mosaic pattern of symptoms in the body.
explain formation of mitochondrial mosaicism
, Nondisjunction is the failure of chromosomes or sister chromatids to
separate properly.
* Meiosis I errors: Failure of homologous recombination or chiasma
formation prevents correct pairing, so homologous chromosomes do
not separate.
* Meiosis II errors / mitosis errors: Failure of sister chromatid separation
due to spindle or cohesion defects.
Molecular causes:
* Recombination defects: improper DNA break repair → weak or absent
chiasmata
* Checkpoint failure (Aurora kinases, Plks): incorrect spindle formation
or attachment is not corrected
* Motor protein failure (kinesin/dynein): chromosomes are not pulled
apart correctly
* Cohesin breakdown errors: sister chromatids stay stuck together too
long or separate too early
➡ Result: gametes with extra or missing chromosomes, leading to
trisomy or monosomy after fertilization
describe how errors in somatic and germ cell division can lead to
trisomy or monosomy and cause human pathology
