Science 9 - Chapter 5 Test Flashcards
clone
identical genetic copy of its parent
Five major types of asexual reproduction used by organisms:
- binary fission (bacteria)
- budding
- fragmentation
- vegetative reproduction
- spore formation
budding
offspring starts as growth/bud on the body of the parent as a result of repeated mitosis and cell divisions
binary fission
organism splits in two roughly equal halves, pinches off (cytokinesis) to form two new organisms. mitosis not necessary because no nucleus in bacteria. single dna just replicates.
what does asexual reproduction mean?
without sex
how does asexual reproduction occur?
occurs without gametes (sex cells) coming together
how can asexual reproduction be characterized?
a. only one parent is required
b. no gametes (sex cells) required
c. offspring are clones (same set of chromosomes)
d. no specialized reproductive cells or structures
fragmentation
pieces of parent’s body breaks off. some fragments produce clones. sometimes occurs by accident. more often, it is deliberate.
ex: sea stars and flatworms reproduce by fragmentation
brain cells are replaced every:
30-50 years
stomach lining cells are replaced every:
2 days
skin cells are replaced every:
20 days
what are the 3 stages of the cell cycle?
interphase
mitosis
cytokinesis
interphase
- cell increases in size, makes protein (carries out the functions necessary for survival)
- cells copy/replicate itself and 3 billion base pairs of DNA information. DNA ladder break apart, new bases pair with bases on original DNA
- cells make proteins for new daughter cells formed after cytokinesis. chromatin (containing replicated DNA) is loosely coiled. dna copied into rna. organelles duplicated. two new identical dna molecules produced
mitosis
divides the duplicated contents of the nucleus into two equal parts
cytokinesis
separates the two nuclei and cell contents into two daughter cells
early prophase
- nucleolus disappears
- spindle fibres begin to form
late prophase
- nuclear membrane disappears
- spindle fibres finish forming and attach to centromeres or chromosomes
metaphase
- spindle fibres pull chromosomes into line at equator
anaphase
- spindle fibres pull sister chromatids to opposite poles of cell
telophase
- spindle fibres disappear
- nuclear membrane forms around each separated set of chromosomes
- nucleolus appears
define vegetative reproduction
only occurs in plants. form new plants without making seeds (without sexual reproduction)
how does vegetative reproduction work?
grasses, lilacs, and many forms send out rhizomes (underground stems.)
some woody shrubs reproduce asexually by using their ordinary stems, branches of these plants take root wherever they touch the ground.
ex: currants, willows, and forsythias
some plants send out runners which are special stems (they have a small, new, genetically identical plant on them.) when new plant touches ground; it roots, forming a whole new plant.
ex: strawberries and spider plants
grafting
- does not happen naturally. humans must make this happen.
- stems called sions are attached to the rooted stock of another species (quicker harvest)
disadvantages of vegetative reproduction
- clones, or new plants, grow close to the parents (compete for same resource)
- clones, or new plants are genetically identical. illness or disease could kill all of them
benefits to humans of vegetative reproduction
- food source (e.g. potatoes)
- increase yield & speed of harvest
- produce crops with specific qualities:
- taste/texture
- storage/handling
- form single-celled spores (specialized reproductive cells)
- have a nucleus, cytoplasm, and protective covering
- covering protects spore from physical damage/drying out
- carried away from parent by wind/water. when spore lands in favourable environment, it develops into a new organism through mitosis.
cytokinesis in plant cells
a cell plate forms
cytokinesis in animal cells
the cell membrane pinches together
in cytokinesis: the 2 nuclei are separated into ________________ that are ____________ the original cell.
2 daughter cells, identical to
why do cells divide?
- cells receive nutrients & removes waste through cell membrane
- size of cell membrane determines how much can enter/leave the cell
- cells grow –> volume increases more quickly than surface area
- once cell is certain size, membrane can’t support contents anymore
- cells must divide to reach favourable surface/volume ration
- when they get too big they divide
What is cloning?
cloning is the process of making a genetically identical organism through nonsexual means
uses of human assisted cloning?
- to save genetic information from endangered species
- to mass-produce an organism with a desirable trait
- (for example pine trees that are resistant to pine beetles)
problems of reproductive cloning (adult DNA cloning)
- only about 10% of clones survive
- clone can be abnormally large/sized
- clones have higher rates of cancer and infection
- clones age faster than others
reproductive cloning (adult DNA cloning)
- produces a genetic duplicate of an organism
- takes a nucleus from a cell (from the organism to be cloned) and puts it into an egg cell that has had the nucleus removed
how is therapeutic cloning used?
to correct health problems
what does therapeutic cloning require?
stem cells
- cells that have not specialized yet –> have the potential to become different types of cells
- can use adult stem cells or embryonic stem cells
which are more desirable to use in therapeutic cloning? adult stem cells or embryonic stem cells? why?
embryonic are more desirable because they can be more types of cells
how can stem cells be used?
to replace damaged cells in patients with diabetes, spinal injuries, or Parkinson’s disease
phases of mitosis
early prophase late prophase metaphase anaphase telophase
stages of interphase
- growth and preparation
- DNA replication
- continued growth and preparation
when are activities within the cell monitored/controlled?
at specific stages/checkpoints
what monitors cell activity. why?
special proteins at the checkpoints monitor the cell activity and send this information to the nucleus.
when will cells not divide?
- not enough nutrients to support cell growth
- dna in nucleus not replicated
- dna damaged
ex; chromosomes not attached to spindle fibres in metaphase, chromosomes not moved to poles in anaphase
what cause mutations?
mutagens (viruses, x rays, ultraviolet light, and chemicals such as acetone in cigarettes.
what happens when a cell is exposed to radiation during mitosis?
chromosomes fail to move to opposite poles of a cell during anaphase
what if a mutation occurred in a gene producing instructions for a checkpoint protein?
cell cycle control will be lost. damaged cells may divide uncontrollably.
what is cancer?
certain diseases that result from uncontrolled cell division
difference healthy cells cancer cells
healthy cells: grow in single layer, stop dividing when they stop receiving messages from nearby cells
cancer cells: don’t respond to messages, begin to grow in multiple layers
what happens to nuclei of cancer cells? why?
become large and abnormal because cell division no longer functions and chromosomes do not divide correctly.
do cancer cells function as parts of your body?
no, cancer cells are not specialized, they do not make proteins for organ cells.
why do cancer cells release chemicals to attract blood vessels?
blood vessels branch into tumour and deliver nutrients to it
how do cancer cells spread?
tumour cells break away and are carried by blood vessels to new location where they divide and form new tumour
what treatment are cancer researchers looking for?
drugs that work by blocking cel division in a cancer cell and preventing formation of tumours
how many times can a human cell divide?
50 times
what are embryonic cells? how long can they live for?
early stage cells of developing embryo. indefinitely.
when/why do embryonic stem cells lose their “fountain of youth?”
once a cell becomes specialized
enzyme in stem cells?
enzyme telomerase
what does telomerase do?
stop chromosomes from tangling/fraying with other chromosomes
how do cancer cells escape programmed cell death? what does this mean for their chromosomes at cells division?
90 percent of human cancer cells don’t turn off telomerase gene. telomere caps of chromosomes do not shorten during cell division (divide longer than regular cells.)
what happens before mitosis?
DNA molecules that replicated during interphase join to form sister chromatids of a chromosome joined by a centromere
three parts/phases of interphase
- growth and preparation
- DNA replication
- growth and preparation continued
