2.6.3- Meiosis Flashcards
What are homologous chromosomes?
Matching chromosomes that contain the same genes in the same loci. They may have different alleles for some of these genes.
What is meiosis?
The type of nuclear division that results in the formation of cells that contain half the number of chromosomes to the parent cell and are genetically not identical to the parent cell.
Explain how genetic variation is increased by genetic variation.
It involves the combining of two unrelated individuals of the same species by fertilisation.
Why is genetic variation within a population needed?
It increases its chances of survival when the environment changes as some individuals will be better suited to the changes.
In many organisms, the body cells are ________.
Diploid.
Got sexual reproduction to take place, the diploid cells must produce _________ _________.
Haploid gametes.
Where does meiosis take place?
In specialised organs called gonads- the ovaries and testes.
Homologous pairs form with one __________ and one _________ chromosome.
Maternal and paternal.
In meiosis, how many divisions are there?
two.
The second meiotic division takes place at ________ ________ to the first.
Right angles.
List all the ways meiosis produces genetic variation.
The crossing over in P1 shuffles the alleles, independent assortment of the chromosomes in A1 and A2 makes the P+M chromosomes randomly distributed, haploid gametes are produces that can undergo random fusion with other organisms gametes.
List the twelve stages of meiosis in order of how they take place.
Interphase 1, prophase 1, metaphase 1, anaphase 1, telophase 1, cytokinesis 1, interphase 2, prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis 2.
List ffour events that take place in the cell during interphase 1.
DNA replicated (s phase)
Organelles duplicated
Growth of cell (G1/2)
DNA replicate to produce sister chromatids.
Naked DNA not wound around just one proteins.
List all the events that take place during Prophase 1 of meiosis.
Chromatids condense and chromosomes supercoil, the chromosomes come together in homologous pairs as crossing over occurs, nuclear envelope breaks down and spindles start to form from centrioles after the centrioles move to opposite poles, chromosomes get shorter and fatter as they condense.
Explain all the events that take place in metaphase 1 of meiosis.
The chromosomes line up along the equator region as spindles attack to the centromere of the chromosomes and the chromosomes are INDEPENDENTLY ASSORTED as each of the pairs face opposite poles of the cell (randomly).
