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General Biology I > Cell Cycle and Replication > Flashcards

Cell Cycle and Replication Flashcards

1
Q

Cell Cycle

A

Mitosis: cell division (only one stage of a cell’s regular cycle)
Many cells constantly move through the stages of the cell cycle which concludes when one cell splits into two new daughter cells
Roughly, the cell cycle can be split into mitotic phase (M-phase) and interphase (everything in between the actual dividing of the cell)
Prokaryotes have an easier time, as they divide through binary fission

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2
Q

Binary Fission

A

Parent cell grows, replicates its chromosome, and then splits in two

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3
Q

Mitosis

A

Separation of the DNA copies to form 2 nuclei
5 steps where sister chromatids split up, with one going to each cell
46 chromatids go to each new cell (daughter cell)
Centrosome (consisting of two centrioles) forms poles at the two ends of the cell and microtubules (called mitotic spindle fibers) stretch the two cells apart

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4
Q

Cytokinesis

A

Splitting of one cell into two

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5
Q

Gap1 Phase (G1 Phase)

A

Is when cells grow after being newly formed, with an emphasis on obtaining energy and forming new proteins (meaning a lot of transcription and translation)

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6
Q

Synthetic Phase (S Phase)

A

Is when the full genome of the organism (all 46 chromosomes in humans) is copied (replication)

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7
Q

Gap2 Phase (G2 Phase)

A

Focuses on further growth and preparations for cell division, including the production of new organelles and proteins needed for mitosis

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8
Q

Mitosis and Cytokinesis Phase or Mitotic Phase (M Phase)

A

A cell splits its DNA copies between two cells, along with its cytosol

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9
Q

Gap0 Phase (G0 Phase)

A

Is when some cells stop growing instead of being in the G1 Phase (they are not working on dividing anymore)
Some cells stay in G0 once they enter it (like differentiated neurons), while others reactivate (like muscle cells when they need to grow further)

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10
Q

CDK

A

Verifies if specific cyclins have been produced to allow a cell to move to the next stage

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11
Q

Cyclins

A

Check points proteins to ensure that a cell is ready for the next stage (for example, cyclin E will bind CDK2 to initiate replication)
Their production is usually accelerated in cancer

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12
Q

Replication (in General)

A

Is like transcription, but on both strands
Permanent separation between the two strands of DNA, since DNA replication is semi-conservative (each new DNA molecule is half old and half new)
The separation stretches away from its initial point (replication bubble) creating a replication fork
DNA polymerase attaches to each strand and uses them to produce complementary strands (both DNA strands are templates)
One strand is copied faster than the other (one of them is leading, and the other one is lagging)
There are many proteins involved in this process
The two new double-stranded DNA molecules are daughter molecules
Occurs at many different spots at the same time

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13
Q

Replication in the Leading Strand

A

A short RNA fragment is produced by primase complementary to the parent DNA strand (template strand)
DNA Polymerase continues from this primer until the end, producing a daughter strand
The RNA fragment is later removed and replaced by by deoxyribonucleotides by RNA polymerase

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14
Q

Replication in Lagging Strand

A

A short RNA fragment is produced by primase complementary to the parent DNA strand (template strand)
DNA polymerase extends from this primer until it reaches a previous fragment
Segments get added backwards, called Okazaki fragments
The RNA fragment is removed and replaced by by deoxyribonucleotides by DNA polymerase
New portion is ligated (attached) to previous fragment
As the replication fork extends, more fragments bind

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15
Q

Replication Steps

A

Open dsDNA and avoid twisting
Prime (initiate) replication with RNA fragments
Produce complementary strands
Replace RNA primer with DNA
Ligate DNA segments (by DNA ligase, which joins the backbone molecules of the fragments)

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16
Q

Unwinding

A

DNA helicase separates the two DNA strands
Single-stranded DNA binding proteins (SSBP) molecules bind to the single strands of DNA to keep them from reannealing (reattach)
Topoisomerase removes DNA twisting tension by breaking phosphodiester bonds, swivels around, and rejoins DNA after relieving tension

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17
Q

DNA Primase

A

Protein that attaches to the ssDNA and synthesizes a short primer of RNA on each strand in a 5’ → 3’ direction

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18
Q

Homologous Chromosomes

A

The pair of chromosomes that are the same (copies)

They are not attached

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19
Q

Sex Chromosomes

A

X and X/Y

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20
Q

Sister Chromatides

A

Copies of each other attached at the centromere

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21
Q

Centromere

A

Region of a chromosome where it can attach to its sister chromatid (and is where they attach after replication)

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22
Q

Kinetochore

A

Hundred of different proteins that holds the centromere onto the cell’s microtubules

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23
Q

Stages of Mitosis

A 
Prophase (early prophase)
Prometaphase (late prophase)
Metaphase
Anaphase
Telophase
A cleavage furrow is created (while the cell stretches wider)
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24
Q

Prophase (Early Prophase)

A

DNA condenses to form chromosomes

Centrosomes move away from each other

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25
Prometaphase (Late Prophase)
The nuclear membrane disappears | The kinetochores attach the chromosomes to the spindle fibres that are between the centrosomes
26
Anaphase
The kinetochores pull the sister chromatids apart, one toward each centrosome
27
Telophase
The chromosomes reach the centrosomes Each set of 46 chromosomes starts to have a nucleus form around it DNA starts to decondense
28
Cytokinesis
In animals, a cleavage furrow develops as the contractile ring closes In plants, golgi-directed vesicles bring cell membrane and cell wall components to the centre of the newly divided plant cell
29
Gametes (Sex Cells)
Cell with half the normal chromosome number | Our only haploid cells
30
Diploids (Somatic Cells)
Make up most of our cells | Have 2n = 46 chromosomes
31
Haploids
Include gametes | Have n = 23 chromosomes
32
Meiosis
Similar to mitosis Instead of having all 46 chromosomes line up, homologous pairs stay together, so only 23 line up (synapsis) After dividing once, the cells divide again (to give four daughter cells) without repeating S-phase
33
Tetrad (Bivalent)
When homologous sister chromatids group together
34
Synapsis
When they group together, homologous sister chromatids cross-over Parts of non-sister chromatids overlap DNA is exchanged between the two homologous chromosomes at chiasma, creating infinite genetic possibilities
35
Chiasmata
Points where synapsis between homologous sister chromatids occurs
36
Independent Assortment
Each gamete has one of the two possible chromosomes (and there are 23 possible chromosomes), creating variation
37
Random Fertilization
Babies come from two gametes, creating variation
38
Crossing Over
Meiosis involves the crossing over of chromatids
39
Spermatogenesis
Male meiosis | Begins at puberty and continues indefinitely
40
Oogenesis
Begins during fetal development but pauses at prophase I Resumes each menstrual cycle, but doesn’t actually finish Only finishes when an egg is fertilized
41
Spermatogenesis
Occurs in seminiferous tubules Cells commit to meiosis (at first called primary spermatocytes, then secondary spermatocytes after meiosis I and later spermatids after meiosis II) Spermatids then develop into sperm cells by growing a tail and finally become spermatozoa
42
Spermatogonia
Performs mitosis (to restock themselves)
43
Leydig Cells (Interstitial Cells)
Located between seminiferous tubules | Produce large amounts of testosterone (stimulating spermatogenesis)
44
Sertoli Cells
Located in the seminiferous tubule Support growing spermatocytes Remove unnecessary waste Help accumulate testosterone in the seminiferous tubules Produce hormones to feedback the brain about spermatogenesis
45
Oogenesis
Starts during fetal development in females Oogonium perform mitosis Primary oocytes stop meiosis I at prophase I Meiosis is resumes during a monthly menstrual/ovulation cycle, but pauses once again until fertilization at metaphase II
46
Follicular and Ovulation Phases
``` Approximately 5 primary oocytes are chosen each cycle to continue meiosis A follicle (one of the cells surrounding primary oocytes to promote oogenesis) Two layers of cells form around the oocyte and eventually guide it to the edge of the ovary, where the oocyte is released (ovulation) The remaining cells become a hormone-secreting structure that stays in the ovary (corpus luteum) ```
47
Luteal and Menstrual Phases
Hormones have caused the lining of the uterus (endometrium) to thicken After ovulation, the oocyte moves from the ovary along the Fallopian tubes, waiting to be fertilized After ovulation, the corpus luteum signals to the uterus to prepare and provide proper nutrients to support an oocyte that is fertilized The corpus luteum only lasts a few weeks: after that, it stops supporting the uterine layer and so menstruation begins and the lining of the uterus is released (unless a fertilized egg arrives in the uterus, in which case it will produce its own hormones that allows the corpus luteum to hang around)
48
Non-disjunction
Flawed gametogenesis (problems) When chromosomes do not separate as they should (either homologous chromosomes in meiosis I or sister chromatids in meiosis II) The result is an egg or sperm with the incorrect number of chromosomes The risk increases with age
49
Aneuploidy
When an organism has the incorrect number of chromosomes 1/160 live births have such a defect The rate would be much higher if most aneuploidy situations weren’t fatal during development Most common aneuploidy with surviving fetuses occurs for chromosomes 13, 18, 21, X and Y
50
Karyotypes
When chromosomes are placed side-by-side, allowing to clearly see which chromosomes are present Can quickly allow to see if someone has aneuploidy or not
51
Fraternal Twins
Originate from the fertilization of multiple eggs
52
Monozygotic Twins
Originate from the spontaneous division of a zygote | Cause conjoined twins
53
Hybridization
Crossing of different species
54
Phenotype
A different display of a trait
55
Generations of Breeding
Parents are the P1 (parental) generation Offspring of P1 is filial generation (F1) Offspring of offspring (F1) produce F2 generation
56
True-breeding (Pure-breeding)
Involves crossing only pure individuals with one another, which always produce offspring having their same trait
57
Alleles
Genes for the same trait Positioned at a specific location on the chromosome (a locus, or loci in plural) Can be dominant (determines the trait if present) Can be recessive (is over-ruled by the dominant trait if present)
58
Homozygous
An organism when both alleles are the same
59
Heterozygous
An organism when the alleles are different
60
Genotype
Allele combination (gene combination)
61
Segregation of Alleles
The separation of homologous chromosomes during anaphase I of meiosis
62
Punnett Squares
Write out genotype of each parent on the two axes (one per axis) and the probability of that allele
63
Test Cross
Involves hybridizing an unknown specimen with a recessive individual F1 offspring will indicate the genotype of the unknown specimen
64
Mendel’s Laws
Law of Segregation | Law of Independent Assortment
65
Law of Segregation
Individuals inherit two copies of each gene, and when forming reproductive cells, each cell only gets one copy
66
Law of Independent Assortment
The two copies of each gene segregate into gametes independently of the two copies of any other gene
67
Addition Rule
When the outcomes being considered cannot occur simultaneously, we add together their individual probabilities
68
Multiplication Rule
When outcomes can occur simultaneously and the occurrence of one has no effect on the likelihood of the other, we multiply their individual probabilities
69
Inheritance Types
Autosomal (dominant and recessive) X-linked (dominant and recessive) Y-linked
70
Incomplete Dominance
For some traits, a heterozygous genotype results in a distinct phenotype We do not use upper & lower case gene abbreviations in this case Crossing F1 × F1 will give parents’ phenotype
71
Multiple Alleles
Many variations of a gene, not just R and r | Individuals still only inherit 2, but now many combinations are possible
72
Co-dominance
When one gene has more than one dominant allele (two alleles can be expressed at the same time and don’t interfere with each other)
73
Pleiotropy
A gene that affects an organism in many ways

General Biology I (8 decks)

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