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chapter 13 Flashcards

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1
Q

What is meiosis?

A
  • It is an alternate form of cell division in eukaryotes.
  • Employed by a subset of cells in eukaryotic organisms.
  • Results in daughter cells that contain half the DNA of the original cell.
  • This is important to the production of gametes: forms the sperm and the egg.
  • Sperm and egg need less genetic material than the other cells in the body, bc when a sperm and egg fuse they restore the normal DNA content in their offspring.
  • It is the process of turning a diploid into a haploid.
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2
Q

What is the DNA triangle?

A
  • Contains three perspectives.
  • DNA can be thought of as a molecule: in it of itself, with a specific primary and secondary structure.
  • Chromosomal perspective: DNA molecules are packed with proteins into structures in the cell called chromosomes.
  • Informational perspective: The sequences of bases on a DNA molecule matters, and each chromosome carries a unique set of information.
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3
Q

Genome?

A

All of the chromosomes and DNA they contain, all genetic information.

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4
Q

Chromosome?

A
  • Separated pieces of the genome.

- With specific regions along the chromosome where specific bases contain the information needed to make a unique RNA.

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5
Q

Genes?

A

Functional unit of the chromosome necessary for the encoding of an RNA molecule

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6
Q

Describe the chromosomes of eukaryotic cells?

A
  • ## Multiple linear chromosomes, usually arranged in pairs (homologous chromosomes).
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7
Q

What is ploidy?

A

the number of sets of chromosomes per cell

di-ploidy= 2 sets of chromosomes per cell type

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8
Q

What is a human’s chromosome number and what kind of ploidy are most eukaryotes?

A
  • Humans are 2n, have 46 chromosomes arrange in to 23 homologous pairs .
  • Most eukaryotes are diploidy.
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9
Q

What is a haploid?

A

It is a cell the only carries one pair of homologous chromosomes.
ex: 1n =11

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10
Q

t/f homologous chromosomes are 100% identical?

explain?

A

False, they have the same structure, size, and gene content, but they lack the exact same version of every gene.
- This is known as two different alleles for the same gene.

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11
Q

What is an allele?

A

Different versions of the same gene.

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12
Q

Maternal homolog?

A

Version inherited form the mother

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13
Q

Paternal homolog?

A

version inherited from the father.

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14
Q

Karyotype?

A

number and types of chromosomes in the cell.
ex: 2n = 12
meaning we have 6 pairs of chromosomes.

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15
Q

Autosome?

A

Any chromosome other than a sex chromosome.

- these do not differ male to female.

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16
Q

Sex Chromosome?

A
  • chromosome associated with an individual’s sex.
  • Like the X and Y chromosome
  • subset of chromosomes that are different between male and females.
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17
Q

T/F: Meiosis is required by organisms that require bisexual reproduction?
Why?

A

True,

  • mom and dad in their diploid state are 2n = 46.
  • Mom XX, and DAD XY
  • If both parents contributed all their chromosomes to their child, it would contain twice as many as it should.
  • SO MEIOSIS: is going to make a haploid sperm and egg so the child gets the regular amount of chromosomes.
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18
Q

T/F mitosis has the same result as meiosis?
Why/why not?
T/F most of the cells in our bodies replicate via meiosis? Why/Why not?

A
  1. ) false, takes diploid cells and creates more diploid cells.
  2. ) False, most of our bodies use mitosis to generate more cells because haploid cells are mainly use for bisexual reproduction purposes.
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19
Q

What are somatic cells?

A
  • Cells that don’t give rise to gametes, vast majority of cells in your body.
  • They divide by mitosis.
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20
Q

How many rounds of division occur in meiosis?

- What cells does this occur in?

A

Germ cells: give rise to sperm or eggs

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21
Q

What is feralization?

What is the product of feralization?

A
  • haploid gametes come together and fuse to create a diploid cell.
  • a zygote (2n)
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22
Q

Describe the Mitosis/meiosis cycle?

A

zygote—>Mitosis(during development)—> Diploid adult/kid 2n—->meiosis (once grown and ready to trade genetic information)

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23
Q

What is the order leading up to meiosis?

A

g1–>s–>g2—>Meiosis

- chromosomes were replicated in the S phase and then enters G2 and then to meiosis as a replicated version .

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24
Q

What is the name for two chromatids between two different members of the same homologous pair?

A

non-sister chromatids.

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25
Q

How many rounds of meiosis is there?

A

2 rounds without DNA replication in-between.

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26
Q

What happens in meiosis one?

what is the result of this step?

A

separates the members of a homologous pair into separate daughter cells.
2.) each cell is now a haploid (one of each chromosome type per cell).

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27
Q

What is meiosis two?

- What is the result of this?

A

The separated daughter cells containing one chromosome is divided further into two separate, making them chromatids, cells-4 daughter cells.
2.) haploids containing one of each chromosome type.

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28
Q

How can we tell a cell is in late stages of G2 that is about to enter meiosis?
- What is this phase called?

A
  • There are two centrosomes, # theyhavedoubled.
  • This better sound familiar bc the same events happen for mitosis.
  • interphase. #step1
29
Q

What is the second phase of the M-phase (meiosis)?
WTF happens in it as well?
During this phase is the cell haploid or diploid?

A
  1. ) Early prophase 1
  2. )
    - spindle apparatus begins to form
    - The replicated chromosomes begin to condense
    - The members of a homologous pair begin to line up and associate. (this is different than mitosis)
    - ———————————————————————–
  3. ) diploid. (2n=6)
30
Q

What is the third phase of the M-phase (meiosis)?
WTF happens in it as well?
During this phase is the cell haploid or diploid?

A
  1. ) late prophase 1
  2. )
    - The microtubules from the spindle apparatus can begin to attach to the microtubules.
    - Non sister chromatids begin to physically interconnect with one-anther (allowing them to exchange pieces with one anther).
    - diploid still
31
Q

What is the forth phase of the M-phase (meiosis)?
WTF happens in it as well?
During this phase is the cell haploid or diploid?

A
  1. ) Metaphase 1:
  2. ) The homologous pairs associate and line up in the middle of the cell , so that one member of each pair is attached to the spindle apparatus.
  3. ) diploid (bearrrllllyy)
32
Q

What is the fifth phase of the M-phase (meiosis)?
WTF happens in it as well?
During this phase is the cell haploid or diploid?

A
  1. ) Anaphase 1
  2. ) The homologs get pulled to opposite ends of the cells.
  3. ) diploid (bearrrllllyy)
33
Q

What is the sixth phase of the M-phase (meiosis)?
WTF happens in it as well?
During this phase is the cell haploid or diploid?

A
  1. ) telophase 1 and cytokinesis.
  2. ) cell divides in half leaving us with two cells containing one version of each chromosome type.
  3. ) were left with two haploid cells.
34
Q

What follows telophase 1 and cytokinesis in meiosis?

A
  • meiosis 2.
35
Q

What is the first step in meiosis 2?

- WTF happens in this step of meiosis?

A
  • prophase 2:
  • the haploid version of prophase one.
  • Spindle apparatus reforms
36
Q

What is the second step in meiosis 2?

- WTF happens in this step of meiosis?

A
  • Metaphase 2:
  • The replicated chromosomes have lined up in the middle of the cell.
  • The spindle apparatus has bond itself to a single sister chromatid, dived in half basically
  • so that half to go to one side and the other half goes to the other.
37
Q

What is the third step in meiosis 2?

- WTF happens in this step of meiosis?

A

Anaphase 2:

- sister chromatid separate

38
Q

What is the forth step in meiosis 2?

- WTF happens in this step of meiosis?

A

Telophase 2 and cytokinesis:

- Cell division is completed.

39
Q

What is the end result of of the second phase of meiosis?

A
  • 4 haploid cells

- each chromosome in its non-replicated state

40
Q

What are the differences between meiosis and mitosis?

A

Mitosis:
- Take a diploid cell in the replicated state.
-their members of homologous pairs don’t associate with one anther.
- each chromosome lines up at the mid line, and you separate the sister chromatids.
- you regenerate two diploid cells.
—————————————————————————
Meiosis:
- cell that is going to undergo meiosis replicated its chromosomes.
- homologous pairs line up , and are separated into different daughters (meiosis 1)
- Meiosis 2 the sister chromatids are separated into different daughter cells
- Resulting in four haploid cell from a single diploid cell to start with.

41
Q

What are the symbols used to represent changes in the DNA?

A

n - is the number of chromosomes types per cell
diploid = two chromosomes types per cell
haploid = one chromosome type per cell
c - keeping track of the total amount of chromatids of a particular chromosome type.

42
Q

2c vs 4c would indicate what?

A

a change from G1 to G2

43
Q

Describe the changes of N and C throughout mitosis?

A
  • We begin with a replicated diploid cell( 4 chromosomes in the diploid state per cell) = 2n,4c
  • We finish with two daughter cells each containing two chromatids for each chromosome type: 2n,2c
44
Q

Describe the changes of N and C throughout meiosis?

A

Meiosis 1:
- we begin with a cell that has undergone DNA replication, so in turn it is 2n 4c
- homologs line up
- homologs separate
- Finally we end meiosis 1 and being meiosis 2,
we have haploid cells n, 2c
MEIOSIS 2:
- we separate sister chromatids from one anther
- We end with daughter cells that are haploid and in the non-replicated state ( single chromatid per chromosome type)
–ENDING: n, c

45
Q

What is the most common problem in meiosis?

- describe whateva that is or skip go and don’t collect two-hunded dollas……

A
  • Nondisjunction: error in the transition form metaphase to anaphase.
    There are a couple options for the what could potentially leave your child with downs(sorry if you known someone with downs):
    1.) separation of homologs in meiosis 1 .
    2.) separation of sister chromatids in meiosis two doesn’t happen equally.
46
Q

What is an example of a nondisjunction chromosomal error?

What is the final results?

A
  • A cell is in metaphase one of meiosis and the homologous pairs are lined up in the midline of the cell #asscioating with each other
  • When we go to anaphase there is an error, and two members on an homologous are so gay they remain associated and don’t split up.
  • now “everybody” (not everyone, but more than orthodox) is on an end of the spindle pole.
  • Following meiosis one, 1/2 daughter cells will contain an extra chromosome and the other will contain one fewer chromosomes.
  • half of the gametes will be n + 1, they’re haploid but they have an extra chromosome, and the other half is n-1: haploid and missing a chromosome.
47
Q

What does it mean to be aneuploidy?

A
  • containing an abnormal number of chromosomes.
48
Q

What is non-disjunction in meiosis two?

A
  • at least one pair of sister chromatids didn’t separate, during anaphase
  • thus, leading to an abnormal # of chromosomes.
  • one cell will have an extra chromosome (n + 1) and one will be missing a chromosome (n - 1).
49
Q

T/F women are more worse than men?

What is true ab the age of women and nondisjunction rates?

A
  • Dr. Reedy actually said they are more likely to have non-disjunctions than men!
  • lots of errors in oogenesis, he said have no girls
    #spermatogenisis is hype.
  • Rates of nondisjunction increase hella as the age of the mother increases
50
Q

Why is nondisjunction more common in older women?

A
  • so sperm are sick and they go immediately from meiotic division one to two.
  • ————–(this line represents superiors and inferiors)
  • cells that begin meiosis, enter into early prophase of meiosis 1 and stop and remain arrested for a long period of time.
  • Then at each round of ovulation a subset of of the oocytes finish meiosis one and enter into meiosis 2.
  • In old women the period of arrest between ,meiosis 1 and 2 is much larger.
  • the more time of arrest = more of a chance to not finish meiosis one correctly.
51
Q

T/F Most gametes produced by the same individual are identical?

A

False, no two gametes produced by the same individual are identical.

52
Q

In what stage of meiosis does tremendous cellular diversity arise in?

A

meiosis 1- in the earlier portion of meiosis, because… the homologous chromosomes in prophase 1 begin to associate with one anther, creating a bivalence.

53
Q

What is a bivalent tetrad?

A

A pair of homologous chromosomes that physically associate with one anther in prophase one and maintain that association all the way through metaphase 1.

54
Q

What are non-sister chromatids?

A
  • two sister chromatids of differing chromosomes within a homologous pair.
55
Q

What are the two events in meiosis one that lead to a tremendous amount of genetic variation?

A
  • independent assortment: the variety of different ways the bivalent pairs can align in the midline of the cell during metaphase 1.
  • ——————————————————————————-Crossing over: The exchange of material of nonsister chromatids of a bivalent.
  • This happens during prophase 1.
56
Q

Describe independent assortment in depth?

A
  • each bivalent arrives independently at the midline of the cells, in what can be a variety of forms.
  • They can then split off into a variety of daughter cell combinations, thus leading to massive amount of variation.
  • If confused look at chapter 13 video 3: 2:30
57
Q

What is the equation to calculate the amount of possible combinations in terms of miosis splitting?
- give the example with humans?

A

1.) 2^x /////////////// x = pairs of homologous chromosomes.
2.) 2^23/////////// x = 23 pairs of homologous chromosomes.
or 8,388,608 different types of gametes from independent assortment alone.

58
Q

What happens first crossing over or independent assortment?

A
  • crossing over, it happens in prophase 1.
  • It occurs when a bivalent forms and non sister chromatids begin to overlap with one anther and possibly exchange segments.
59
Q

What is a Chiasma?

A
  • point of physical connection between non sister chromatics in a tetrad during prophase 1.
60
Q

Why are chiasma importane?

A

por que es que allows for crossing over!!!!

61
Q

What is crossing over?

A
  • at the chiasma .
    • at the chiasma, crossing over happens.
  • you can have homologous regions where non sister chromatids physically overlap with one anther.
  • then breaking…. and causing the DNA repair systems to put everything back together and swapping the homologous regions of non sister chromatids when they do so.
62
Q

What is genetic recombination?

A

-the product of crossing over where the DNA repair system puts everything back together after the chiasma break with regions of non sister chromatids (genetic stuff that doesn’t belong to that sister chromatid )

63
Q

T/F you get different patterns of genetic variation as a result of differing patterns in crossing over, from one cell to the next?

A

True.

64
Q

T/F independent assortment and crossing over occur dependent of one anther?

A

false, they are independent of each other.

65
Q

What is asexual reproduction?

A
  • reproduction through mitosis.
  • no fusion of gametes
  • clones of parent
66
Q

What is sexual reproduction?

- what are its mechanisms?

A
  • gametes are formed through meiosis and those gametes fuse to make a new diploid individual.
    2. ) Selfing: one individual is capable of making both types of gametes.
  • transgender, or hermaphordidic .
    3. ) Outcrossing- sexual reproduction where gamete reproduction is via two individuals.
  • MUCH GREATER CHANCE FOR GENETIC DIVERSITY.
67
Q

What type of reproduction leads to the fastest outcome of a new population?

A
  • a sexual reproduction.
    in outcrossing, only the females are responsible for sexual reproduction. Asexual reproduction everyone and their dog can sexually reproduce.
68
Q

What is the purifying selection hypothesis?

A
  • think about this Mr.White:
    -an individual has a bad allele and a good allele but the individual is heterozygous for that bad gene.
  • ## with a lack of genetic diversity these individuals will struggle to survive, as that bad deleterious allele continues to swarm the population.BUT if the homies reproduce by outcrossing.
  • then only half their gametes will contain that crappy allele.
  • therefore it lowers the population of deleterious alleles.
69
Q

What is the changing hypothesis theory?

A
  • genetic diversity ,as a result of outcrossing, allows the population to be more resilient as a whole if the environment where to change.
  • illustrated with the round worms that can reproduce via outcrossing and selfing,
  • the round worms use selfing 80% of the time and outcrossing 20% of the time.
  • when added a bacteria pathogen evolving at a fast rate, those that reproduce via outcrossing survived as a result of genetic diversity.

Biology 202: (39 decks)

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