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Genetics PMY-3 > L01 Meiosis > Flashcards

L01 Meiosis Flashcards

1
Q

All cells share:

A
  • DNA(genetic material)
  • Plasma membrane
  • Ribosomes
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2
Q

Discuss living organisms that have genetic material(not including viruses)

A
  • Prokaryotes( bacteria and archaebacteria)

- Eukaryotes (Animal, plant, fungus, protist(eukaryotic cell that is not one of the others))

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3
Q

Describe the cell structure of prokaryotic cell

A
  • Prokaryotes are typically a unicellular organism
  • surrounded by plasma membrane
  • PM protected by cell wall
  • Prokaryotes contain no organelles, DNA and proteins and lipids are free in the cytoplasm
  • cell wall surrounded by a capsule (or slime layer or glycocalyx ) made up of polysaccharides and glycoproteins
  • ribosomes in cytoplasm
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4
Q

Describe DNA in a prokaryotic cell

A

DNA is organized in a nucleoid region in the cytoplasm

Semi circular DNA call the plasmid is also found in the cytoplasm, this is not genomic DNA

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5
Q

Briefly describe reproduction in prokaryotes

A

Cell division in prokaryotes is asexual reproduction very similar to mitosis

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6
Q

Describe how prokaryotes transmit genetic material

A

DNA is first replicated by enzymes and substrate(deoxynucleotides)

DNA molecules separates in to two cells

Also known as binary fission (act of dividing or splitting into two)

Daughter cells is exactly like the parent cell, same amount of DNA

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7
Q

Describe the cell structure of the eukaryotic cell

A
  • Cell surrounded by a cell membrane
  • Free ribosomes in cytoplasm but there is also on the rough endoplasmic reticulum
  • mitochondria
  • nuclear envelope: membrane barrier separating the nucleus from cytoplasm
  • centrioles
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8
Q

Describe the centrioles of eukaryotic cells

A

2 cylindrical structures made of a protein tubulin and surrounded by a pericentriolar material, during cell division the pericentriolar material contains proteins that help with spindle fiber assembly

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9
Q

What are somatic cells ?

A

In animals, reproductive cells give rise to spermatozoa and ova

Somatic cells are all other cells

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10
Q

How do eukaryotes transmit genetic materials?

A

On chromosomes via mitosis and meiosis

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11
Q

Give a brief description of meiosis

A

Meiosis leads to the production of sex cells

-gametes or spores with half the genetic material of the parent cell(half the chromosomes, haploid)

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12
Q

Give a brief description of mitosis

A

Mitosis leads to the production of two cells from the parent cell

- each with the same amount of genetic material as the parent cell
- Walther Fleming , German anatomist named this because he saw the formation of paired threads
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13
Q

How are chromosomes converted to chromatin?

A

When the cells are not dividing, the chromosomes are diffuse within the nucleus and it is chromatin

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14
Q

What happens when it is time for the cell to divide?

A
  • the DNA duplicates
  • the DNA starts to become organized, gets packed and becomes organized to the condensed chromosome structures we recognize by distinctive shape and sizes
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15
Q

In diploid organisms, chromosomes exit in …..

A

Homologous pairs

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16
Q

Explain the aspects of homologous chromosomes

A
  • similar but not identical
  • one from each parent (biparental inheritance)
  • homologous pairs carry all the same genes
  • sometimes slight difference between mom and dads genes
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17
Q

Homologous chromosomes pairs carry all the same genes, elaborate on this

A
  • Identical regions along a chromosome are called a locus
  • this is true for 22 chromosomes that are called autosomes
  • the exception is the sex chromosome pair, X and Y chromosomes which have some unique, sex determining genes
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18
Q

Describe how many chromosomes are in humans

A

Somatic cells have homologous chromosomes

Humans have 46 chromosomes (23 homologous pairs )

This is the human diploid number(2n)

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19
Q

What are meta centric chromosomes?

A

Chromosomes with the centromere located in the middle

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20
Q

What are submetacentric chromosomes?

A

Chromosomes with the centromere located between the middle at the end

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21
Q

What are Acrocentric chromosomes?

A

Chromosomes with the centromere located close to the end

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22
Q

What are telocentric chromosomes?

A

Chromosomes with the centromere located at the end

Seen in mice, not in humans

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23
Q

What are holocentric chromosomes?

A

Centromere consists of the entire length of the chromosome

Seen in C elegans, not in humans

24
Q

The top, petition arm of the chromosome is the …

A

P arm

25
Q

The bottom, longer arm is the…

A

q arm

26
Q

What happens in metaphase?

A

The DNA is duplicated, two copies of the same chromosome

27
Q

Two copies of the same chromosome attached by a centromere are called…

A

Sister chromatid

28
Q

Describe a Karyotype

A

The metaphase chromosomes from a cell are photographed and the chromosomes are cut out and organized based on chromosome shape.

29
Q

Describe sex determining chromosomes

A
  • Not homologous in size
  • Not homologous in centromere placement
  • Y lacks most of the gene loci that X has, as it is smaller
  • Must contain homologous REGIONS to behave as a Homologous chromosomes during meiosis
  • Not homologous in arm ratio(p and q)
30
Q

How are chromosomes treated for Karyotyping and why?

A

Chromosomes treated with a protease so that the sister chromatid are only a associated at the centromere

Then stained with Geimsa

31
Q

What is a zygote?

A

A single celled fertilized egg of multicellular organisms

The fertilized egg will now enter the cell cycle

32
Q

What is cytokinesis?

A

The part of the cell cycle, cytoplasmic division completes the formation of daughter cells

33
Q

What is karyokinesis?

A

Part of the cell cycle, when the cell is ready to divide, all of the DNA(46 chromosomes) is duplicated then one complete set is separated from the other set during nuclear division for the formation of daughter cells.

34
Q

What are the discrete stages of mitosis?

A

(PPMAT)

P- prophase
P- prometaphase 
M-metaphase 
A-anaphase
T-telophase
35
Q

State the events of interphase

A

Two gap phases G1 and G2

- Some cells enter G0 where it withdraws from the cell cycle”quiescent”
- G0 is a point in G1 where cells are nondividing but metabolically active
- G1 and G2 have intensive metabolic activity and cell growth and cell differentiation

S phase is when DNA is synthesized

36
Q

Give the time interval/duration of each phase in interphase

A

G1 - 5 hours

S phase- 7 hours

G2- 3 hours

37
Q

Interphase is characterized by …

A

The absence of visible chromosomes

38
Q

What is the longest part of mitosis?

A

Prophase

39
Q

State the occurrences of prophase

A
  • Centrioles divide and move apart to establish poles
  • Chromosomes coil, condense and become visible
  • Spindle fibers begin to organize at the centrioles
40
Q

State the occurrences of prometaphase

A
  • chromosomes begin to move to the equatorial plane/metaphase plate of the cell
  • Centrioles reach the poles of the cell
  • Spindle fibers form and become organized
41
Q

State the occurrences of metaphase

A
  • Centromeres align at the metaphase plate
  • The centromere is attached to two spindles, one from the top and bottom
  • Each spindle wants to associate with one sister chromatid
42
Q

What is the most common phase of mitosis fir Karyotyping.

A

Metaphase

43
Q

The migration to the metaphase plate is only possible by the binding of…

A

The spindle to the chromosome’s kinetochore and centromere region

44
Q

What is the kinetochore region?

A

An assembly of proteins associated with the centromere region

45
Q

What is Cohesin?

A

a protein complex that holds sister chromatids together

46
Q

What is Separase?

A

An enzyme that degrades cohesin

47
Q

What is Shugoshin?

A

A protein that protects cohesin from being degraded by separase

48
Q

State the events of Anaphase

A

Sister chromatids separate/disjoin- disjunction

Sister chromatids move to the opposite poles of the cell

 - Shigoshin must be degraded
 - Cohesin are cleaved by separase
49
Q

Separated sister chromatid are now called…

A

Daughter chromosome

50
Q

Movement of daughter chromosome is dependent on…

A

Kinetochore-spindle fiber attachment

51
Q

State the events of Telophase

A
  • Daughter chromosomes arrive at the poles
  • Reformation of the nuclear envelope around each set of chromosomes
  • Spindle fibers disperse into microtubules
  • Cytokinesis occurs to divide the cytoplasm between the 2 daughter cells
  • Daughter cells enter interphase
52
Q

What may prevent the cell from going from G1 to S?

A

The environment of the cell is not favorable to proceed to S phase

The cell is not right and DNA is not good

53
Q

What may prevent a cell from going from G2 to Mitosis?

A

All the DNA has not been replicated faithfully

The cell environment is not favorable to enter mitosis

54
Q

What may prevent a cell from going from Metaphase to Abaohase?

A

The sister chromatids are not ready to separate

Not all the chromosomes are not attached to the spindle and kinetochores

55
Q

Explain the functioning of the proteins that regulate the cell cycle

A

Governed by hetero-dimers made of:

  • Cyclins
  • CDK proteins (cyclin dependent kinases)

These dimers accumulate in the cell at premise times to trigger the cell to proceed to the next stage

56
Q

How can protein hetero-dimers lead to cancer?

A

Mutations in proteins, hetero-dimers often lead to cancer/ uncontrolled cell division

57
Q

Discuss genetic content “n” and chromosome number “c” in mitosis

A

S phase, G2 and mitosis has 2n and 4c

G1 has 2n 2c

Genetics PMY-3 (27 decks)

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