Lesson 3: Sexual Reproduction Flashcards

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1
Q

what is sexual reproduction

A

form of reproduction in which individuals are produced from the fusion of two sex cells (sex cells usually come from two different parent organisms)

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2
Q

advantages to sexual reproduction and provide examples

A
  • individuals that rely on sexual reproduction can adapt to a changing environment, due to their genetic variability which is not possible in organisms that reproduce asexually
  • this can support the long term survival of a species

for instance, a pack of rabbits are residing somewhere, when wolves suddenly come into their environment and reside there too- the rabbits that run fast will survive and the rabbits that dont will not survive
- basically, if all rabbits were slow and genetically identical, as soon as the wolves come, they would all die and the species would have less chance of survival and possibly go extinct

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2
Q

disadvantages to sexual reproduction

A
  • specialized organs are required to produce the sex cells
  • specialized mating calls or bright colours to attract mates can also attract predators
  • may require the loss of resources, like nectar in flowers
  • the combining of genetic information may make the offspring weak and unable to survive
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3
Q

what are the two key processes in sexual reproduction

A
  • formation of haploid cells, or gametes, which contain genetic information from the parents
  • two sex cells joining together to form a zygote, the first cell of a genetically unique individual, through fertilization
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4
Q

what is meiosis

A

this is the process through which haploid gametes are formed; it involves two divisions that produces 4 haploid gametes from 1 diploid parent cell

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5
Q

gametogenesis

A

formation of sex cells

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6
Q

what are the two types of gametogenesis in humans

A
  • formation of sperm by spermatogenesis
  • formation of egg cells or ova by oogenesis
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7
Q

growth stage: interphase

A
  • cell grows to nearly twice in size
  • nucleus makes a copy of its DNA
  • organelles are also replicated
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8
Q

meiosis 1: prophase 1

A
  • chromatin condenses into chromosomes
  • nuclear membrane dissolves
  • centrioles move to opposite sides of the cells
  • spindle fibers begin to grow
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9
Q

meiosis 1: prophase 1 (what are tetrads and how are they formed- through what process are they fomed)

A

homologous chromosomes come together and intertwine to form a tetrad by a process called synapsis

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10
Q

what is a tetrad

A

four sister chromatids together is called a tetrad

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11
Q

meiosis 1: prophase 1 (crossing over, what is it and how does it occur)

A

crossing over may occur at this stage
- when intertwined chromatids from different chromosomes break off and reattach at the chiasmata
- this causes an exchange of genetic material at certain sections
- it works to mix or recombine genetic information, further increasing the genetic variation in the gene pool

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12
Q

meiosis 1: metaphase 1

A

the tetrads migrate towards the center of the cell, called the equatorial plate
- spindle fibers are attached at the centromeres of the chromosomes
- the tetrads align their centromeres in the middle of the cell

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13
Q

meiosis 1: anaphase 1

A

homologous chromosomes move to opposite poles of the cell when the spindle fibers shorten
- this means that only one of the two chromosomes from each homologous pair will be in each new daughter cell and therefore are genetically unique
- ex: each of your sperm or egg has only the chromosome you received from your mom or your dad, not both

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14
Q

meiosis 1: telophase 1

A

the nuclear membranes reform, spindle fibers dissolve, and the cell begins to divide via the first cycle of cytokinesis (each new cell has only 1 and not 2 duplicated copy of a chromosome at this point)
- only the maternal or paternal chromosome is in each new cell
- therefore, cells are haploid

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15
Q

meiosis 2: prophase 2

A

each haploid cell has one chromosome made of two sister chromatids at this point
- the sister chromatids are not genetically identical due to crossing over that occurred during prophase 1
- nuclear membrane dissolves, centrioles move to opposite poles, and spindle fibers reform

16
Q

meiosis 2: metaphase 2

A

the chromosome move to the center of the cell, called the equatorial plate
- accomplished through spindle fiber attachment at the centromeres
- the chromosomes align their centromeres in the middle of the cell

17
Q

meiosis 2: anaphase 2

A

sister chromatids now seperate and move to opposite poles of the cell
- each cell now has a single sister chromatid, not a duplicate copy
- these will not be identical due to the genetic exchange that occurred in crossing over

18
Q

meiosis 2: telophase 2

A

the nuclear membrane reforms around the chromatids, the DNA relaxes into chromatin, and the spindle fibers dissolve

19
Q

meiosis 2: cytokinesis for the second time

A

cytoplasm splits and results in 4 haploid daughter cells that are not identical

20
Q

what allows for genetic variation in meiosis

A
  • crossing over in prophase 1
  • in metaphase 1 and 2, it is random as to which side each chromosome goes to
21
Q

what is the male reproductive cell called

A

sperm (contains 50% of the father’s genes)

22
Q

what is the female reproductive cell called

A

the egg (contains 50% of the mother’s genes)

23
Q

fertilization

A

when the two cells join together, the genetic material combines (essentially the joining of reproductive cells is fertilization)

24
Q

diffferent types of fertilizations?

A
  • some animals like humans go through internal fertilization, where the egg is fertilized inside the body; the offspring develop inside the mother
  • some animals like fish have external fertilization; the female releases her eggs, then the male fish spreads his sperm over her eggs- the young basically develop outside of the body