Lab 4 Flashcards
what is Asexual reproduction
done through mitotic cell division, results in offspring which are genetically identical to the parent organism
organism which reproduce sexually produce…
genetically variable offspring
what does meiosis produce
gametes (egg and sperm) in animals and spores in plants
what does ploidy refer to
the number of “sets” of chromosomes found in a cell
what are diploid organisms
they have two sets of chromosomes in their cells; for every chromosome in the nucleus there is another chromosome that is the same size, shape, and carrying the same genes (AKA homologous chromosomes)
what are homologous chromosomes
they have two sets of chromosomes in their cells; for every chromosome in the nucleus there is another chromosome that is the same size, shape, and carrying the same genes
when referring to diploid organisms or cells what format do we use
2n=number of chromosomes
i.g. most human cells are diploid and contain 46 chromosomes in 23 homologous pairs which is written as 2n=46
do all animals have the same amount of chromosomes
not they do not
what are haploid cells
they only have one type of chromosome in the nucleus (there is no homologous partner for each chromosome)
i.g. eukaryotes are said to he haploid
when referring to haploid organisms or cells what format do we use
n=number of chromosomes
are human gametes haploid or diploid?
they are haploid; they have the haploid number of chromosomes so n=23
what is interkinesis
an interphase like stage between meiosis one and two. but unlike interphase there is no DNA replication, and this stage is usally very short
what is done in meiosis two
it separates replicated chromosomes into single chromosomes
what happens in prophase two
-replicated chromosomes condense again
-new spindle apparatus forms
what happens in pro metaphase two
-nuclear envelope disintegrates again
-spindle microtubules attach to the centromeres of each replicated chromosome
what happens in metaphase two
replicated chromosomes line up individually along the metaphase plate of each daughter cell
what happens in anaphase two
centromeres of each replicated chromosome separate and the resulting single chromosomes are moved to opposite poles by the spindle apparatus
what happen in telophase two
-single chromosomes arrive at opposite poles and start to uncoil
-spindle apparatus disappears
-nuclear envelopes will reform
-nucleoli will become visable
-cytokinesis begins
-at the end of tel 2 there will be 4 daughter cells, each containing the haploid number of single chromosomes (n=2)
what happens in prophase 1
-replicated chromosomes condense
-spindle microtubules begin to form
-homologous chromosomes pair up (process called synapsis) form tetrads
-genetic exchange occurs between homologous chromosomes during a process called crossing over
what happens in prometaphase 1
-nuclear envelope disintegrates
-spindle microtubules attach to centromeres of each replicated chromosome
what happens in metaphase 1
-tetrads are lined up along the midregion (metaphase plate) of the cell
what is anaphase 1
the homologous chromosomes separate form each other and are moved to opposite poles of the cell by the spindle apparatus
what happens in telophase 1
-replicated chromosomes arrive at poles and begin to uncoil
-spindle apparatus disappears
-nuclear envelopes start to reform
-cytokenesis begins (by furrow in animal cells and cell plate in plant)
-at the end of telophase 1 each daughter cell contains the haploid number of replicated chromosomes (n=2)
how and where does meiosis occur in plants
in diploid cells sporocytes within reporductive organs called sporangia to form haploid spores
how can you determine weather a particular cell is in division one or two in a lily anther
the final product of meiosis in the lily anther if four haploid cells called microspores. the four cells will seperate from one another and each one will devide by mitosis to become a mature pollen grain
what things can you label when labeling a lily anther slide
-cell wall
-cytoplasm
-chromosomes
-cell plate and spindle where applicable
what is alternation of generations
-plants have a complex life cycle and that is what its called.
-it means that they have distinct multicellular haploid and diploid stages
what is the diploid generation of the plant life called and what does it produce
its called the sporophyte
it produces haploid spores by meiosis within the structures called sporangia
what is sporangia
the haploid spores by meiosis within the structures
what is gametophyte
when spores (sporangia) undergo metosis to produce multicellular haploid gametophyte
what happens within gametophyte
reporductive organs will produce gametes (sperm and eggs) by mitosis
most sporophyte dominat meaning…
the multicellular diploid stage is the most obvious stage of the life cycle
what is the life cycle of a fern polypodium like
it althernates between the dominant multicellular diploid stage and a smaller, independent multicellular haploid stage
what kind of lifecycle does lily and chives have
a sporophyte dominant life cycle
what are pollen grains
the tiny male gametophytes of flowering plants
what does the large fern leaves grow out from
horizintal underground stem called rhizome which bears many roots
in most ferns what develops on the underside of mature leaves
brown spots called sori (singular sorus)
what should you be able to identify on a sorus slide
sporangium
sporangial stalk
spores
what happens when spores land in suitable areas of soil
they will germinate and if conditions are favourable it will divide mitotically to produce a multicellular haploid gametophyte generation
what is the ferns gametophyte
typically a tiny hear shaped plant (also called prothallus)
each gametophyte developed fine, root like structures called rhizoids on its surface
on ferns groups of cells on the underside of the gametophyte develop into…
reproductive organs called antheridia (male) and archegonia (female)
mitosis in antheridia gives rise to… and…
flagellate sperm cells while single egg cell develops in each archegonium
what happens when flagellate sperm cells are mature
they are released from the antheridium and swim in a film of water to the archegonium to fertilize an egg cell
what happens after fertilization of a fern gametophytes
the diploid zygotes develops by repeated mitotic divisions into a new sporophyte plant
how do sporophyte meet there nutritional requirements
initially the sporophyte is nutritonally dependent on the gametophyte in which it is embedded. once the sporophyte develops roots and photosynthetic leaves the gametophyte degenerates
what is crossing over
in animal cells the exchange of genetic material between non sister chromatids of homologous chromosomes
when does the process of crossing over occur
during prophase 1 of meiosis
what is the region in which crossing over occurs in
it occurs in a region called chriasma (plural chrismat)
in animals meiosis only occurs in… and results in the production of…
ovaries and testes, haploid gametes (egg or sperm)
what happens when the the haploid egg and sperm combine during fertalization
they form a diploid zygote cell which develops into the new multicellular diploid individual by mitosis
meiosis 1…
halves the number of chromosomes ie… diploid to haploid
meiosis 2…
separates replicated chromosomes into single chromosomes (these cells are already haploid)
