4.3 - Meiosis Flashcards
What is a haploid cell?
A cell containing half the usual number of chromosomes
Example: Sex (stem) cells
What is a diploid cell?
A cell containing 2 copies of each chromosome
What is meiosis?
A 2 stage cell division in which resulting daughter cells have half the number of chromosomes as the parent cell; forms gametes (sex cells)
What is mitosis?
A single division resulting in 2 identical daughter cells (identical to each other & parent)
How many daughter cells does meiosis produce?
4 non-identical haploid daughter cells (gametes)
What occurs during interphase I?
Growth & DNA replication
What happens during prophase I of meiosis?
Chromosomes shorten & thicken, exchange genetic information, and are now 2 sister chromatids.
These chromosomes come together in homologous pairs, called tetrads, and is a process called synapsis. Crossing over (mixing of non-sister chromatids of a homologous pair) occurs.
What is a tetrad?
A pair of homologous chromosomes, each chromosome has 2 sister chromatids, so in total 4 chromatids
What is synapsis?
Physical pairing of homologous chromosomes during prophase I of meiosis
What is crossing over?
Exchange of chromosome segments between homologous pairs during synapsis (prophase I), resulting in recombination of genetic information between non-sister chromatids of a homologous pair
What occurs during metaphase I?
Tetrads move to the centre of the cell, aligning their centromeres across the middle of the cell.
What happens during anaphase I?
Homologous chromosomes move to opposite poles of the cell. Reduction division occurred, where only 1 chromosome from each homologous pair will be found in each new daughter cell.
What is telophase I?
Nuclear membranes begin to form around chromosomes at each end of the cell, and the cell divides, becoming 2 haploid cells
What is spermatogenesis?
Production of sperm cells
What is oogenesis?
Production of egg cells
Is there interphase II?
NO
What happens during prophase II?
Nuclear membrane dissolves and spindle fibers begin to form.
What happens during metaphase II?
Chromosomes arrange across the middle of the cell, each with 2 sister chromatids attached at the centromere.
What happens during anaphase II?
Sister chromatids separate and move to opposite poles of the cell.
What happens during telophase II?
Nuclear membrane forms around the chromatids, now called chromosomes.
Mitosis vs. Meiosis
Mitosis: Single division, identical daughter cells, 46 chromosomes in end, diploid daughter cells, makes new body cells
Meiosis: 2 divisions, non-identical daughter cells, 23 chromosomes in end, haploid daughter cells, makes gamete (sex cells, sperm & egg) cells
Somatic cells are …
Body cells
Ex. skin cells, bone cells, nerve cells
Homologous chromosomes
similar in shape, size, & genetic information. Humans have 23 homologous chromosomes in our body cells (22 pairs of autosomes & 1 pair of sex chromosomes). They separate during Anaphase I.
