Ch 13 Meiosis Exam 3 Flashcards
Homologous Chromosomes
-chromosomes that are the same size and shape
Autosomes
-not associated with sex determination
Sex Chromosomes
-determine an organism’s sex
Allele
-differences in genes
-example: eye color
Diploids
-two homologs of each chromosome
-example: the 2 in 2n
Haploids
-one of each type of chromosome
-equals n
Meiosis
-one round of DNA replication followed by two rounds of cellular division
-the back-to-back divisions are Meiosis I & Meiosis II
Meiosis I
-reduces the number of chromosomes
Meiosis II
-division is the same as in Mitosis
Interphase in Meiosis
-pre-meiotic S-phase
-chromosomes replicate
Prophase I in Meiosis
-homologs come together
-involves breaking and connecting together DNA
Metaphase I in Meiosis
-kinetochore microtubules move bivalent pairs to metaphase plate
-each bivalent straddles the metaphase plate with one homolog on each side
-the alignment of each bivalent is independent of other bivalents
Anaphase I & Telaphase I in Meiosis
-sister chromatids remain together
-cytokinesis results in reduction of chromosome numbers
Meiosis I Description
-results in daughter cells that have one chromosome of each homologous pair
-daughter cells are haploid
-chromosomes in each cell randomly assorted due to crossing over and random distribution of maternal and paternal
Mitosis v. Meiosis Differences
-homolog pairing in meiosis
-crossing over
Meiosis Increases Diversity
-chromosomes in gamete differ from the parent cell
Asexual Reproduction
-any mechanism of producing offspring that doesn’t involve gametes
-resulting daughter are genetically identical to mothers
Sexual Reproduction
-production of offspring by mating and fusion of gametes
-offspring are genetically distinct from parent cells
Chromosomes & Heredity
-in the body 23 homologous pairs of chromosomes
-46 chromosomes in total
-half from mom & half from dad
-each chromosome contains genes
Law of Independent Assortment
-each gene will sort independently
Genetic Recombination
-new combinations of alleles
Crossing Over
-produces new combinations of alleles within a chromosome
-combined with independent assortment
-incredible amount of genetic diversity
Self-Fertilization
-the offspring are genetically distinct from the parents
Outcrossing
-when gametes from one individual combine with another
Down Syndrome
-caused by trisomy of chromosome 21
Nondisjunction
-when the sister chromatids do not separate
-results in aneuploidy
Aneuploidy
-one cell has the incorrect number of chromosomes after meiosis and fertilization
Paradox of Sexual Reproduction
-need one member of each sex to produce progeny
-only females can produce progeny
-results in less individuals over time
