MEIOSIS - MAIN TERMS Flashcards
HOMOLOGOUS CHROMOSOME PAIR
when one pair comes from the mother and the other comes from the father
ensures organism has the characteristics of both parents
KARYOTYPE
the complete diploid set of chromosomes within a somatic cell of an organism
MITOSIS
the division of somatic cells, and helps with growth, repair of damaged tissues and asexual reproduction
two daughter cells produced
CROSSING OVER
- hom chro arrange in pairs
- bivalent forms
- sister chromatids visible
- crossing over and exchange of segments occur
- hom chro pair after
PURPOSE OF MEIOSIS
the formation of sex cells/gametes in the sex organs of animals
GAMETOGENESIS
gamete formation
SPERMATOGENESIS
sperm formation
OOGENESIS
egg formation
REDUCTION DIVISION
meiosis, bc diploid chromosome no. is reduced to haploid
IMPORTANCE OF MEIOSIS
- diploid chromosome number is halved to prevent chromosomes from doubling w each gen
- leads to genetic variation
- prod spores in plants and gametes in animals
GENETIC VARIATION
differences that occur as a result of diff gene combinations between organisms of a species
DIFF GENE COMBOS ARE OBTAINED BY
crossing over
random assortment of chro on the equator
random fertilization
ABNORMAL MEIOSIS
when meiosis does no proceed as normal, resulting in a change in no or structure of chromosomes
ANEUPLOIDY
when there are extra or missing chromosomes in a cell
DOWN SYNDROME
when there are 47 chromosomes instead of 46, because chromosome pair no 21 does not separate during Anaphase 1
DOWN SYN CHARACTERISTICS
- small almond shaped eyes
- large tongue
- flat forehead, nose bridge
SIMILARITIES
both cell division processes
both require DNA rep during Interphase
both have PMAT
DIFFERENCES
no variation in Mit (identical dau cells)
variation in Mei (by crossing over)
two dau cells in Mit, four dau cells in Mei
no crossing over in Mit, yes in Mei
CHROMOSOME
occur in the nucleus of every living cell
CHROMOSOME STRUCTURE
DNA molecule wrapped around proteins (histones)
GENE
DNA segment that controls a particular inherited characteristic
diploid chromosome number
2n
double set of chromosomes
GAMETES
sex cells
egg / sperm
one set of chromosomes
zygote
formed when the egg and sperm fuse
two sets of chromosomes
human karyotype
22 pairs of autosomes and one pair of gonosomes
46 (dip chro num)\
ie.) 44 + XX - female
44 + XY - male
INTERPHASE
the period between two consecutive cell divisions
when cell DNA replication and cell growth take place
prophase of Mit
chromatin net shortens and thickens to become visible as chromosomes nucl mem and nucleolus disappear centrosome duplic centrioles move to opp poles spindle fibres develop
metaphase of Mit
chromosomes position in a single row on the equator
spindle fibers attach to centromeres
anaphase of Mit
each centremere divides into two
chromatids separate and move to opposite poles
now known as daughter chromosomes
cytokinesis begins
telophase of Mit
daughter chro position at poles spindle fibers disappear nuc mem and nuclelous form cytokinesis two identical daughter cells are formed
meiosis defintion
a reduction division where the chromosome number of each cell is halved, from dip to hap
first meiotic division
chro number is halved and genetic material is changed
second meiotic divison
proceeds like normal mitosis where chromatids/daughter chro separate
polyploidy
the condition where there are more than two sets of chromosomes in a cell, more common in plants
