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1
Q

Are autosomal cells haploid or diploid?

A

Diploid (2n, contain two copies of each chromosome)

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2
Q

Are germ cells haploid or diploid?

A

Haploid (n, contain one copy of each chromosome)

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3
Q

What is Interphase?

A
  • includes the first 3 stages of cell cycle (G1, S, G2)
  • longest part of cell cycle
  • 2 centrioles come together to form a centrosome – helps hold chromosomes apart
  • chromosomes are uncondensed
  • individual chromosomes are not visible with light microscopy b/c they are in chromatin form (less condensed form where DNA is available to RNA Poly for transcription)
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4
Q

What is the G0 stage?

A

stage where cells that do not divide spend all of their time, cell just performs its function

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5
Q

What happens during the G1 stage?

A
  • Presynthetic gap
  • cells create mitochondria, ribosomes, ER
  • cells increase in size
  • DNA is examined and repaired at restriction point (determines if cell can enter next stage)
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6
Q

What happens during the S stage?

A
  • Synthesis of DNA
  • cell replicates its DNA
  • after replication each chromosome has 2 identical chromatids bound together at the centromere
  • have 92 chromatids organized into 46 chromosomes organized into 23 homologous pairs
  • 2x as much DNA as cells in G1
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7
Q

What happens during G2 stage?

A
  • Postsynthetic gap
  • cell continues to grow & replicates organelles in preparation for mitosis
  • cell continues to perform its normal functions
  • goes through 2nd quality control checkpoint
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8
Q

What happens during M stage?

A
  • Mitosis (cell division)

- cytokinesis (splitting of the cytoplasm and organelles into two daughter cells)

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9
Q

What composes a chromatid?

A

a complete double-stranded molecule of DNA

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10
Q

What is a sister chromatid?

A

identical copies of eachother

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11
Q

When can the term chromosome be used in the cell cylce?

A
  • before S phase when referring to a single chromatid

- after S phase when there is a pair of chromatids attached at the centromere

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12
Q

What is the result of division in autosomal cells?

A

2 genetically identical daughter cells

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13
Q

What is the result of division in germ cells

A

2 non-equivalent germ cells

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14
Q

When are the checkpoints in the cell cycle?

A
  • between G1 and S phase

- between G2 and M phase

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15
Q

What occurs at the G1/S checkpoint?

A
  • known as the restriction point
  • cell determines if DNA is good enough for synthesis
  • if there is damaged DNA then cell goes into arrest until DNA is repaired
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16
Q

What is the main protein in control during the G1/S checkpoint?

A

p53

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17
Q

What occurs at the G2/M checkpoint?

A
  • ensure the cell has achieved adequate size and organelles have been properly replicated
  • makes proteins for mitosis
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18
Q

What protein plays a role during the G2/M checkpoint?

A

p53

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19
Q

What molecules are responsible for the cell cycle?

A

cyclins & cyclin-dependent kinases (CDK)

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20
Q

Explain the process of cyclin & CDK binding and what they do

A

cyclins bind to CDKs to create an active CDK-cyclin complex (MPF - mitosis promoting factor) that can then phosphorylate transcription factors that promote transcription of genes required for the next stage of the cell cycle

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21
Q

How does cancer occur?

A

results when cell cycle control is deranged and damaged cells still undergo mitosis

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22
Q

What gene is most commonly mutated in cancer?

A

TP53 (gene that produces p53)

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23
Q

What is metastasis?

A

spread of cancerous cells through the blood stream or lymphatic system

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24
Q

What is mitosis?

A
  • process by which two identical daughter cells are created from a single cell
  • occurs in somatic cells
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25
Q

What are the phases of mitosis?

A

PMAT

  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
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26
Q

What is a centrosome?

A

contains two tubulin-based centrioles responsible for proper movement of chromosomes

27
Q

(1) What occurs during prophase?

(2) What occurs during Prometaphase?

A

(1)

  • condensation of chromatin into chromosomes – chromosomes condense
  • centriole pairs (located outside the nucleus in the centrosome) separate and move towards opposite poles of cell
  • at opposite poles of cell the centrioles begin to form spindle fibers / mitotic spindle (made of microtubules)
  • some microtubules form asters (anchor centrioles to cell membrane) and others extend toward middle of cell

(2)

  • nuclear membrane dissolves so spindle fibers can contact the chromosomes
  • kinetochores appear at centromere and serve as attachment points for fibers of the spindle apparatus that are called kinetochore fibers
28
Q

What occurs during metaphase?

A
  • centriole pairs located at opposite ends of cell
  • chromosomes gather along metaphase plate in center of the cell under guidance of spindle apparatus
  • chromosomes are madeup of two sister chromatids that are still attached to one another (pair of sister chromatids = one chromosome_
29
Q

What occurs during anaphase?

A
  • centromeres split so each chromatid has its own distinct centromere and sister chromatids can separate
  • sister chromatids pulled toward the opposite poles of the cell by shortening of kinetochore fibers
30
Q

What occurs during telophase?

A
  • spindle apparatus disappears
  • nuclear membrane reforms around each set of chromosomes
  • nucleoli reappear
  • chromosomes decondense back into chromatin
  • cell divides into two identical daughter cells
31
Q

What is meiosis?

A
  • occurs in gametocytes (germ cells)

- results in up to 4 non-identical sex cells (gametes)

32
Q

What are similarities between mitosis and meiosis?

A
  • genetic material is duplicated
  • chromatin is condensed into chromosomes
  • microtubules from centrioles are involved in dividing genetic material
33
Q

What are differences between meiosis and mitosis?

A

-consists of one round of replication followed by two rounds of division

34
Q

How many homologous pairs of chromosomes (homologues) does the human genome have?

A

23 (with one chromosome inherited from each parent)

35
Q

What are sister chromatids?

A

identical strands of DNA connected at the centromere

36
Q

What are the phases of meiosis?

A 
Meiosis 1
-prophase 1
-metaphase 1
-anaphase 1
-telophase 1
Meiosis 2
-prophase 2
-metaphase 2
-anaphase 2
-telophase 2
37
Q

What occurs during prophase 1?

A
  • chromatin condenses into chromosomes
  • spindle apparatus forms
  • synapsis: process by which homologous chromosomes come together and intertwine, each chromosome now consists of 2 sister chromatids so each synaptic pair contains 4 chromatids and is called a tetrad
  • crossing over: occurs when chromatids of homologous chromosomes break at the poi t of contact (chiasma) and exchange equivalent pieces of DNA, increases genetic diversity
38
Q

What is a synaptonemal complex?

A

group of proteins that hold homologous chromosomes together; part of tetrad

39
Q

What is linkage?

A
  • associated with crossing over
  • tendency of genes to be inherited together
  • genes located farther from eachother are less likely to be inherited together and more likely to undergo crossing over relative to eachother
40
Q

How does crossing over explain Mendel’s 2nd Law?

A
  • law of independent assortment

- states that inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes

41
Q

What occurs during metaphase 1?

A
  • homologous pairs (tetrads) align at metaphase plate and each pair attaches to a separate spindle fiber by its kinetochore
  • at this phase in mitosis each chromosome is lined up at the plate but is attached to two spindle fibers – one fro each pole
42
Q

What occurs during anaphase 1?

A
  • homologous pairs separate and are pulled to opposite poles of cell
  • disjunction: each chromosome of paternal origin separates from its homologue of maternal origin and either chromosome can end up in either daughter cell thus distribution of homologous chromosomes to 2 intermediate daughter cells is random with respect to paternal origin
43
Q

What is segregation?

A
  • occurs during anaphase 1

- separating of 2 homologous chromosomes

44
Q

What law does anaphase 1 follow?

A

Mendels 2nd Law of independent assortment

45
Q

What occurs during telophase 1?

A
  • nuclear membrane forms around each new nucleus (each chromosome consists of 2 sister chromatids joined at centromere)
  • cells now haploid (23 chromosomes)
  • cell divides into 2 daughter cells by cytokinesis
46
Q

What is interkinesis?

A
  • occurs during telophase 1 between cell divisions

- short rest period that sometimes occurs between cell divisions and chromosomes may partially uncoil

47
Q

What is the result of meiosis 1?

A
  • homologous chromosomes are separated
  • chromosome number is halved (reductional division)
  • daughter cells have haploid number of chromosomes (23)
48
Q

What occurs during prophase 2?

A
  • nuclear envelope dissolves
  • nucleoli disappears
  • centrioles migrate to opposite poles of cell
  • spindle apparatus begins to form
49
Q

What occurs during metaphase 2?

A
  • chromosomes line up on the metaphase plate

- 1 chromosome per daughter cell

50
Q

What occurs during anaphase 2?

A
  • centromeres divide
  • chromosomes separate into sister chromatids that are pulled to opposite poles by spindle fibers
  • 2 chromosomes in each daughter cell
51
Q

What occurs during telophase 2?

A
  • nuclear membrane forms around each new nucleus
  • cytokinesis follows and 2 daughter cells are formed
  • final product is 4 haploid daughter cells per gametocyte
  • one chromosome in each daughter cell
52
Q

What is the result of meiosis 2?

A
  • separation of sister chromatids (equational division)
  • more similar to mitosis than meiosis 1
  • 4 haploid daughter cells with one chromosome in each
53
Q

Mitosis Key Points

A
  • 2n -> 2n
  • occurs in all dividing cells
  • homologous chromosomes do not pair
  • no crossing over
54
Q

Meiosis Key Points

A
  • 2n -> n
  • occurs in sex cells only
  • homologous chromosomes align on opposite sides of metaphase plate
  • crossing over can occur
55
Q

What is biological sex determined by?

A

the 23rd pair of chromosomes

56
Q

What are kinetochores?

A
  • proteins and RNA around the centromere

- facilitates the binding of microtubules to the spindle

57
Q

At the end of mitosis, ____ gets degraded while ___ stays around in its inactive form

A
  • cyclin (concentration fluctuates)

- CDK (concentration remains constant)

58
Q

___ activity represents the start of mitosis

A

MPF
(cyclin and CDK bound together
)

59
Q

Proto-Oncogenes

A
  • genes that aid in cell growth
  • gene that is active during checkpoint
  • this is the form that is not mutated
60
Q

Oncogene

A
  • mutated form of the proto-oncogene
  • permanently turned on form of the proto-oncogene so surpasses all checkpoints
  • cell is unable to stop growing
  • “gain of function” mutation
61
Q

Tumor Supressor Genes

A
  • typically inhibit growth
  • when mutated it becomes non-functional and can no longer inhibit growth
  • “loss of function” mutation
62
Q

Apoptosis

A
  • coordinated collapse of the cell
  • protein degradation and ladder-like DNA fragmentation occur
  • neighboring cells engulf the leftover cell bits
  • important in embryonic cell death
  • cell shrinks (condensation)
  • membranes stay intact
  • ATP required
  • only affects individual cells
63
Q

What makes a cell decide to undergo apoptosis?

A
  • withdraw positive growth signals (ex. take away growth factor for neurons)
  • receipt of negative signals (includes increased levels of oxidative damage, DNA damage, death activators like FasL)
64
Q

Necrosis

A
  • cellular swelling
  • ATP depletion
  • cell lysis (burst) which leads to an inflammatory reaction
  • membranes are broken
  • DNA is fragmented randomly and smeared
  • in vivo, whole areas of tissue are affected

SP MCAT Biology (21 decks)

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