Meiosis Flashcards
Define Chance: (stats)
The occurrence of events in the absence of any obvious cause.
Define Continuous variation:
Variation in which organisms do not fall into distinct categories but show gradations from one extreme to the other.
Define Crossing over:
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged.
Define Diploid:
A term applied to cell in which the nucleus contains two sets of chromosomes.
Define Discontinuous variation:
Variation in which organisms fall into distinct categories.
Define Fertilisation:
The fusion of two gametes, bringing together the DNA from each.
Define Gamete:
The reproductive cell that fuses with another gamete during fertilisation.
Define Genetic variation:
Differences in DNA base sequence between two or more organisms, with the possibility of resulting in different alleles.
Define Haploid:
Term referring to cells that contain only a single copy of each chromosome.
Define Homologous chromosomes:
A pair of chromosomes , one maternal and one paternal, that have the same gene loci and therefore determine the same features.
Give an example of a gamete (human):
Human egg or sperm.
What type of cell is a gamete such as a sperm cell.?
Haploid.
Give an example of a haploid cell:
Gametes such as Sperm or Egg cells.
Define Independant segregation:
The process by which maternal and paternal copies of homologous are randomly distributed to gametes during meiosis.
Define Meiosis:
The type of nuclear division in which the number of chromosomes is halved.
Define Random fertilisation:
Where any one male gamete could fuse with any one female gamete.
Define Random sample: (stats)
A subset of population in which each member of the subset has an equal probability of being chosen.
Define Standard deviation: (stats)
A measure of spread of values around the mean average.
Meiosis is the special cell division used by sexually-reproducing organisms to make what cells?
Gametes.
What is the purpose of meiosis and sexual reproduction?
To introduce genetic variation.
What is the purpose of genetic variation?
It allows species to adapt to their environment and so to evolve.
During meiosis what is the initial and final product?
Meiosis produces four genetically different haploid cells from one diploid cell.
T / F:
In meiosis, there are four identical haploid cells are produced.
False - The cells are genetically different.
What is the main usage of meiosis?
To provide gametes for sexual reproduction.
Why is a haploid cell required for sexual reproduction?
Because one haploid cell from each parent fertilize to make a diploid number.
Why is genetic variation an advantage to a species?
The species can adapt to a changing environment and evolve over time.
What is the ‘ploidy status’?
A measure of the number of chromosomes in one cell.
What is the ploidy status of a human haploid cell?
(1)n = 23
What is the ploidy status of a human diploid cell?
2n = 46
T / F:
All haploid cells have 23 chromosomes.
False - Humans have 23, however, chimps have 24.
T / F:
All diploid cells have 46 chromosomes.
False - Humans have 46, however, chimps have 48.
How many times does karyoinesis occur?
Twice.
When is the bivalent formed?
Prophase I.
When does recombitance (crossing over) occur?
Prophase I.
