Chapter 11 - Meiosis And Sexual Reproduction Flashcards

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1
Q

Haploid cells are produced by a type of cell division called what?

A

Meiosis

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2
Q

Gametes unit to form what? Which has two sets of chromosomes (one from each gamete)

A

A zygote

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3
Q

Cells with two sets of chromosomes are called what? While one set is called what?

A

2 sets - diploid (2n)

1 set - haploid (n)

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4
Q

Sexual reproduction requires diploid cells to do what with their chromosome count?

A

Reduce their chromosome number by half and produce haploid cells, otherwise it would double the chromosomes every generation

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5
Q

Meiosis always starts with what type of cells and the daughter cells being what type?

A

Starts with diploid ends with haploid

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6
Q

How does meiosis achieve the reduction in chromosome number?

A

By undergoing one round of nuclear replication immediately followed by 2 rounds of nuclear reduction

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7
Q

What is the difference in named stages from mitosis to meiosis?

A

Meiosis has the same name but 2 stages of each. Pro/meta/ana/telophase 1 and 2 instead of just 1.

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8
Q

Are G1, S, and G2 similar to mitosis in meiosis?

A

Yes, virtually identical

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9
Q

What happens in prophase 1? (Be very specific) include as much details as possible.

A

-Homologous (in form of sister chromatids) are brought together forming a synaptonemal complex of four chromatids

-a dense lattice of proteins tightly pairs the homologous called synapsis, during synapsis the genes of the sister chromatids align precisely with each other

-the precise alignment of homologous non-sister chromatids allows for crossing over (exchange of the ends of the homologous non sister chromatids, visible as chiasmata)

-a short area of homology attaches the X and Y chromatids in males

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10
Q

What is crossing over and what does it do?

A

Crossing over is a form of genetic recombination between nonsister chromatids (mothers and fathers homologues)

-it mixes mother and father genes producing recombinant chromosomes (red and blue)

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11
Q

What does recombination nodules do? And what are they?

A

They are large proteins complexes that mark the location of chiasmata in the process of crossing over

-an enzyme cuts the double strand of DNA and makes new connections between nonsister chromatids

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12
Q

When the synaptonemal complex breaks down, the homologous chromosomes are attached only at what point?

A

The chiasmata and centromers

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13
Q

The groups of four chromatids when visible are called…

A

Tetrads

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14
Q

In terms of DNA exchange what does crossing over do in simple terms?

A

It leads to one chromosome having both maternal and paternal DNA

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15
Q

What happens in prometaphase 1?

A

-Spindle fiber microtubules attach to kinetochore proteins at the centromeres

-each member of the homologous pair attaches to the opposite pole assuring that the homologous pairs are pulled apart at metaphase 1

-homologous chromosomes are still held together at the chiasmata

-nuclear membrane breaks down completely

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16
Q

What happens at metaphase 1? (Be specific) list as much detail as possible.

A

-homologous chromosomes align on metaphase plate

-homologous pair align themselves randomly regarding which side they are on (maternal vs paternal) -(random alignment and crossing over accounts for genetic variation)

-orientation of each tetrad is independent of the orientation of the other 22 tetrads

17
Q

Diploid cells is denoted as 2^n representing the number of chromosomes per haploid set for n, what could this number be in humans?

A

2^23 being over 8million possible genetically distinct gametes just from one independent assormtnet alone

18
Q

What happens in anaphase 1?

A

-microtubules pull the homologous chromosomes apart

-the sister chromatids remain tightly bound at their centromeres

-the chiasmata are broken

19
Q

What happens in telophase 1? And cytokinesis

A

Seperated chromosomes arrive at opposite poles, a cleavage seperates the two daughter cells in cytokinesis

20
Q

Meiosis 2 will produce how many haploid cells when the sister chromatids seperate?

A

4

21
Q

What happens between meiosis 1 and 2? What is this phase called?

A

Not much, the time discrepancy is brief, no interphase occurs and is called interkinesis

22
Q

What is more similar to mitosis, meiosis 1 or 2?

A

Meiosis 2, only major difference is that there are half the number of chromosomes present

23
Q

Since meiosis 2 is pretty similar to mitosis, in brief terms go through each step (in order)

A

Prophase 2) MTOCs reform new spindles at opposite ends of each cell

Prometaphase 2) each sister chromatid forms an individual kinetochore that attaches to microtubules from opposite poles

Metaphase 2) sister chromatids align at the equilateral plate

Anaphase 2) sister chromatids are pulled apart by the kinetochore microtubule and moved towards opposite poles, nonkinetochore microtubules elongate the cell

Telophase 2, and cytokinesis) chromosomes arrive at opposite poles and begin to decondense, nuclear envelop develops around the chromosomes, cytokinesis separates the two cells into four unique haploid cells

(These 4 cells are genetically unique to random assortment in metaphase 2 and recombination during crossing over)

24
Q

Why is sexual reproduction so vital? Hense why asexual organisms are rare

A

Because variation is important for survival and reproducing populations, EVOLUTION.

25
Q

Plants have a strategy of multinuclear diploid and haploid stages called what?

A

Alternation of generations

26
Q

Specialized diploid cells are produced in the gonads in embryonic development called what?

A

Germ cells

27
Q

Germ cells first undergo what time of division? Then what after?

A

They undergo mitosis and eventually meiosis

28
Q

A zygote is formed when haploid cells produce two mating types (+/-) but does not undergo mitosis but immediately meiosis producing what?

A

4 haploid cells called spores

29
Q

What happens to the spores?

A

They can remain dormant and eventually will divide by mitosis to produce multinuclear haploid bodies

30
Q

Diploid dominant life cycles, haploid dominant life cycles, and both diploid and haploid dominant life cycles are seen in what species/organisms respectively?

A

Diploid dominant life cycles - animals

Haploid dominant life cycles - fungi and some algae

haploid and diploid dominant life cycles - some algae and all plants

31
Q

What is the haploid dominant stage and diploid dominant stage called in life cycles that do both? What does it produce?

A

Haploid dominant stage is called the gametophyte (produces hanged by mitosis since its cells are already haploid)

Diploid dominant stage is called sporophyte (produce spores that grow into haploid plants called gametophytes)