Bio Chapter 11 Flashcards
Meiosis
Reduces the number of chromosome sets from diploid to haploid
Meiosis takes place in 2 consecutive cell divisions (meiosis I and II)
Results in 4 daughter cells - Each daughter cell has only half as many chromosomes as the parent cell
Phases of meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I and cytokinesis
Period between meiosis I and meiosis II
Period before meiosis I and II
Interkinesis
Interphase
Phases of meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II and cytokinesis
Very similar to mitosis
Interphase
DNA synthesis and chromosome replication phase
Meiosis I
4n to 2n, separate chromosomes
Meiosis II
Separate chromatids
Prophase I
Mother and father cross over and exchange
Chromosome pairs with its homolog
Tetrad
Four sister chromatids of two homologous chromosomes
Chiasma/chiasmata
Location where two chromosomes cross
Metaphase I
Pairs of homologs line up at the metaphase plate with one chromosome facing each pole
Microtubules from one pole are attached to the kinetochore of one chromosome of each pair
Microtubules from the other pole are attached to the kinetochore of the other chromosome
Anaphase I
Pairs of homologous chromosomes separate
One chromosome of each pair moves toward opposite poles guided by the spindle apparatus
Sister chromatids remain attached at the centromere and move as one unit toward the pole
Telophase I
Each half of the cell has a haploid set of chromosomes
Each chromosome still consists of 2 sister chromatids
Cytokinesis
Usually occurs simultaneously
Forms 2 haploid daughter cells
Animal cells form cleavage furrow
Plant cells form cell plate
Interkinesis
Nuclear membrane re-forms around chromosomes, spindle breaks down and chromosomes relax
No chromosome replication
Prophase II
Spindle apparatus forms
Chromosomes move toward the metaphase plate
Metaphase II
Sister chromatids are arranged at the metaphase plate
Kinetochores of sister chromatids attach to microtubules extending from opposite poles
Anaphase II
The sister chromatids separate and move to opposite poles
Telophase II
Chromosomes arrive at opposite poles, nuclei form and chromosomes begin de-condensing
Cytokinesis in meiosis II
Separates the cytoplasm
Egg
XX
Sperm
XY
Autosomes
Any chromosome that isn’t a sex chromosome
Homologous chromosomes
Includes one chromosome from each parent
46 chromosomes in a human somatic cell are 2 sets of 23 (1 from mother and 1 from father)
Asexual reproduction vs. sexual
Asexual is a single individual passes all of its genes to its offspring, so it’s genetically identical
Sexual is 2 parents give rise to offspring that have combination of genes from the 2 parents
Sexual is better because it has genetic variation
