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FoM > Histology + Cells + Tissues (W1) > Flashcards

Histology + Cells + Tissues (W1) Flashcards

1
Q

minimum hours a cell cycle lasts

A

12h

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2
Q

cell cycle protein molecules

A

cyclins A,B,E

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3
Q

what do the cell cycle protein molecules (cyclins A,B,E) activate?

A

CDKs (cyclin dependent kinases)

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4
Q

interval between the end of mitosis and beginning of next is called

A

interphase

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5
Q

Period in which DNA is synthesised. What promotes this synthesis?

A

S phase + promoted by cyclin A and CDKs

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6
Q

TIME FRAME of S phase in mitosis

A

8h after end of mitosis
takes 7/8 hours to complete

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7
Q

lists some possible ways the DNA can be damaged during replication (mitosis)

A
  • Deoxynucleotide incorporation error during replication
  • by spontaneous deamination of bases
  • various chemicals that interact with DNA
  • x-radiation causing NICKS in the DNA
  • UV irradiation
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8
Q

what are nicks in the DNA

A

single strand breaks

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9
Q

what is mismaatch repair (MMR)

A

a DNA repair mechanism that corrects errors that occur during DNA replication, specifically base mismatches and small insertions or deletions that can arise when the DNA polymerase incorporates the wrong nucleotide or slips during replication.

Prevents mutations from being passed on to daughter cells.

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10
Q

what is homologous recombination

A

refers to the exchange of genetic material between two homologous (similar or identical) DNA molecules. These homologous sequences are typically found on sister chromatids or homologous chromosomes.

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11
Q

xiroderma pigmentosum - changes in the skin and why

A

a rare genetic disorder characterized by extreme sensitivity to ultraviolet (UV) radiation, particularly from sunlight

People with XP have a defective DNA repair mechanism, specifically in the nucleotide excision repair (NER) pathway, which normally fixes DNA damage caused by UV light.

These mutations impair the ability to repair UV-induced damage, specifically thymine dimers (abnormal covalent bonds between adjacent thymine bases(thymine dimers/pyrimidine dimers) on a DNA strand, caused by UV exposure)

develop SQUAMOUS CELL CARCINOMA on the skin

As a result, individuals with XP accumulate DNA damage in their skin cells, leading to a higher risk of skin cancer and other skin-related abnormalities.

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12
Q

what is RAD51

A

DNA repare protein encoded by the gene RAD51. (it is an enzyme) - during homologous recombination

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13
Q

what is homologous recombination in meiosis

A

homologous recombination happens during meiosis I, which leads to the formation of gametes (sperm and egg cells). This process contributes to genetic diversity by creating new combinations of alleles.

ALSO

Proper Chromosome Segregation: In meiosis, it helps in the proper segregation of homologous chromosomes into gametes by ensuring they are physically connected, allowing them to align correctly at the cell’s equator.

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14
Q

what is homologous recombination in mitosis

A

DNA Repair: repair of DSB (double-stranded breaks) in DNA

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15
Q

How is homologous recombination used in CRISPR-Cas9

A

This genome-editing tool often relies on homologous recombination to integrate a desired DNA sequence after a double-strand break is induced by the Cas9 protein.

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16
Q

what is BRCA1/BRCA2 and what is its function

A

gene involved in repairing DNA through homologous recombination

its dysfunction, leads to genomic instability

increased risk of cancer

17
Q

what is G1 in mitosis + what is it controlled by

A

between end of mitosis + beginning of S phase

cell responds to growth factors
these frowth factors, instruct the cells to undergo mitosis

once the cell decides to do so, there is no going back, irreversible process.

+ syntehsis of moelcular machinery needed for mitosis

CONTROLLED BY: Cyclin E + CDKs

18
Q

what does cyclin E+CDKs control

A

control G1 phase in mitosis

19
Q

length of time for G1 phase in mitosis

A

variablewh

20
Q

what is G0 phase in mitosis

A

cells which have retained the capacity for proliferation, but are no longer dividing - QUIESCENT, they do NOT enter the S phase

this phase is between G1 and S
remembrer (M-> G1 -> (G0) -> S)

21
Q

gene mutated in retinoblastoma + what is it

A

Rb
tumor suppressor gene
causing DISEASE x

normally, Rb blocks the mitotic cycle in G1 phase (cell becomes quiescent)

22
Q

What is G2 phase in mitosis

what is it controlled by

A

the gap between the end of S pahse and beginning of mitosis i nthe G2 phase

cell prepares for division

this period ends with breakdown of nuclear membrane and the onset of chromosome condensation

CONTROLED by cylin B+ CDKs

23
Q

what does cyclin B+CDKs control

A

G2 phase in mitosis

24
Q

time duration of G2 phase in mitosis

A

2-4h to complete in mitosis - stage

25
Q

interphase

A

a stage in which individual chromosomes are not visible - uncoiled

nucleus of cell possess a nuclear envelopes which contains a network of chromatin threads or granules + nucleolus

26
Q

what happens in prophase of mitosis

A
  • each chromosome splits longitudinally into 2 chromatids except at the centromere
  • the two paired centriole are separated from each otehr by elongation of continuous microtubulues of the achromatic spindle and occupy the oppotsite poles of nucleus
27
Q

what happens during prometaphase

A

nuclear membrane and nucleolus disappear

chromosomes entangled in a meshwork of continuous microtubules

1.5h

28
Q

what happens during metaphase

+ duration

A

centromere region from each chromosome presents a bilateral disc KINETOCHORES

a set of chromosomal mircotbules are organized and extend from the kinetochores bialterally towards opposite centrioles

the centromere of individual chromosomes with their paired chromatids occupies equatorial plane of the spindle – facilitated by the growth of chromosomal microtubules

20 MIN

29
Q

what are kinetochores and where are they found

A

bilateral disc present at the centromere region - arises from each chromosome

30
Q

what happens during anaphase of mitosis

A

chromosomal microtubules contract + exert force in centromere region

centromeres split longitudinally and chromatids separate to form 2 new chromosome

spindle fibres contract, chromsomes newly formed separate and migrate to the opposite pole of the spindl

31
Q

what happens during telophase (IN PROGRESS) of mitosis

A

new nuclear membrane forms + nucleolus appears

chromosomes uncoil

cytoplasm divides + 2 complete cells are formed

32
Q

what happens during telophase (COMPLETE ) in mitosis

A

cleavage furrow develops around the equator region of achromatic spindle , during cytokinesis

contraction of fibrillar component of cytoplasm help in hour glass constriction of cleavage

33
Q

What is non-disjunction

A

refers to the failure of sister chromatids to properly separate during the anaphase stage of mitotic cell division. This results in an unequal distribution of chromosomes between the two daughter cells, where one cell may receive an extra chromosome (gain) and the other may receive one less chromosome (loss).

34
Q

what is iscohromosome in mitosis

A

a type of chromosome abnormality that occurs during cell division (mitosis or meiosis) when a chromosome divides horizontally/transversely, instead of the normal vertical separation. As a result, the two arms of the chromosome (typically referred to as the p arm and q arm) are mirror images of each other, and both halves of the isochromosome will have identical genetic material from either the short arm (p) or the long arm (q) of the original chromosome.

35
Q

what is colchicine

A

Inhibits Microtubule Polymerization:
* X by binding to tubulin, a protein that assembles into microtubules, which are part of the cytoskeleton.
* Microtubules are essential for a variety of cellular processes, including cell division (mitosis), intracellular transport, and the maintenance of cell shape.
* X By binding to tubulin, prevents the formation of microtubules, disrupting processes that rely on them, particularly cell division.

Effect on Mitosis:
* Since X disrupts microtubule formation, it also prevents the proper separation of chromosomes during mitosis. This characteristic makes X useful in laboratory settings for studying cell division, and it has been used in karyotyping to arrest cells in metaphase so that chromosomes can be easily examined.

ALSO undeprins rationale for many types of cytotoxic drugs in cancer therapy

36
Q

hernia

A

the bulging of an internal organ through a weak are or tear in the muscle or other tissue that holds it in place

37
Q
A

FoM (14 decks)

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