Topic 11 - Asexual And Sexual Reproduction Flashcards
What is asexual reproduction?
A process where new cells or organisms are produced without the fusion of gametes.
What are the advantages and disadvantages of asexual reproduction?
ADVANTAGE - large number of individuals created quickly, ideal for unchanging environnement.
DISADVANTAGE - lacks genetic variation in population
What is sexual reproduction?
Process where new individuals formed from fusion of gametes and pollen to form a zygote.
What are the advantages and disadvantages of sexual reproduction?
ADVANTAGES: provides genetic variation
DISADVANTAGES: energy expended in finding a mate, slower, signals sent to prospective mate may attract predators.
Describe asexual reproduction in prokaryotes.
BINARY FISSION
- contain one circular molecule of DNA
- binary fission simpler and faster
- occurs in 20 minutes
- exponential growth
Describe budding.
Unequal cytoplasm division, new organism grows on parent and breaks away.
Describe parthenogenesis.
Type of cloning, results in formation of new individuals from unfertilised egg.
What is crossing over?
Mutual exchange of pieces of chromosome and genes between homologous chromosomes. Occurs after homologous chromosomes have synapses to form bivalents in prophase I. Crossing over occurs at specific points called chiasmata. Recombination of alleles occurs as a consequence of crossing over. Recombinants are the chromosomes formed.
What is regeneration?
Part of organisms breaks off and regenerates into new individual eg flatworms, sea worms, sea stars.
What is spore formation?
Spores released into environment and germinate into new individual.
FUNGI
What is vegetative propagation?
Runners, rhizomes, tubers, bulbs and suckers.
When cut, the develop into new organisms.
Describe embryo cloning.
Female cow given FSH to superovulate, eggs collected and fused with desirable sperm. In vitro fertilisation occurs. 4 cells from 16-cell embryo taken and implanted into 4 surrogate mothers.
Result: each calf born is a clone of its siblings, not either parent.
Describe limitations of nuclear transfer.
- low success rate
- few embryos implanted survive to full term
- clones may have abnormalities
- telomeres become shorter - DNA ages faster than the time period from which animal was born
What is meiosis?
Meiosis is the process of cell division that results in the production of new cells each containing half the number of chromosomes of original cell.
What is the effect of independent assortment?
Creating new combinations of maternal and paternal chromosomes in gametes.
Describe the process of somatic cell cloning (nuclear transfer).
From sheep A, cells are taken from udder tissue. Thus, a somatic cell is taken.
From sheep B, eggs are collected after sheep is given FSH to super-ovulate. The nucleus is removed from an egg - enucleated.
The somatic cell from sheep A is fused with sheep B’s enucleated egg. Electric pulse is used.
Egg is then cultured in vitro to a 16 cell embryo.
Embryo is then implanted into surrogate mother, sheep C.
Lamb is born who is genetically identical to sheep A as the nucleus is received from sheep A.
What is the function of the centromere?
Joins together the sister chromatids of a double stranded chromosome.
Is the region where the kinetochore is located, attachment site where sister chromatids are pulled apart during Anaphase of Mitosis and Anaphase II of Meiosis.
What is an advantage of producing cloned crops and what is a disadvantage?
Farmer knows the genetic composition of the crop. Can select crops to grow for high productivity and desirable traits.
However, crops are genetically identical which is unideal in changing environment. If one crop fails, all the crops fail.
What is the effect of crossing over?
The exchange of genetic material occurs at points - chiasmata. Results in recombinant chromatids consisting of paternally and maternally derived DNA creating genetic variation.
What is independent assortment?
Where homologous chromosomes randomly align on either side of the metaphase plate during Metaphase I of Meiosis.
Name the first stage where Mitosis differs from Meiosis and how so?
Prophase I. In both, chromosomes condense, spindle starts forming from centrioles, nuclear envelope disappears.
In Meiosis, chromosomes attach to nuclear membrane and synapse to form bivalents of homologous pairs. Crossing over and recombination occurs. In mitosis this does not occur.
Difference between metaphase I in Meiosis and mitosis?
In Meiosis, homologous chromosomes assort randomly on either side of the metaphase plate.
In mitosis, all chromosomes line up on the metaphase plate. They do not form homologous pairs.
Difference between anaphase I in Meiosis and mitosis?
In Meiosis, homologous chromosomes are separated and pulled to either pole of the spindle. Half to one pole and half to the other.
In mitosis, the spindle fibres attach to kinetochores of the centromeres of the chromosomes, and separates the sister chromatids segregating them to opposite poles of the spindle.
What is external fertilisation?
Animals release gametes into external environment - fertilisation occurs outside female body.
Produces large numbers of gametes to increase chance of fertilisation.
