Unit 5a- Meiosis and Sexual Life Cycles Flashcards
Genes
segments of DNA that code for basic units of heredity
What is the two types of Reproduction?
asexual and sexual
Asexual reproduction
produces clones (genetically identitcal)
single parent
little variation in populations - through mutations
fast and energy efficient
Sexual reproduction
meiosis produces gametes
2 parents
lots of variation/diversity
slower and energy consumptive
Mitosis
body cells
somatic
diploid
2n
Meiosis
sex cells
gametes
haploids
n
Homologous chromosomes
includes 1 chromosome from each parent, with the same allele
Autosomes
22 pairs of chromosomes that do not determine sex
Gametes
22 autosomes and 1 sex chromosomes
Karyotype
a picture of an organism’s complete set of chromosome
Fertilization and mieosis
alternate in sexual life cycle
Meiosis is
cell division that reduces the number of chromosomes , creates gametes of 23 chromosomes
Meiosis = Reduction Division
cell divide twice
result 4 daughter cells , each w/ half as many chromosomes as parent cell
Prophase I
crossing over at the chiasmata occurs
homologous chromosomes pair up
Synapsis
homologous chromosomes pair up
Tetrad
4 sister chromatids
Metaphase I
tetrads line up
Anaphase I
pairs of homologous chromosomes separate
sister chromatids still attached by centromere
Telophase I & Cytokinesis
Haploid set of chromosomes in each cell
Each chromosome = 2 sister chromatids
Inter phase happens before
prophase I
Prophase II
no interphase
no crossing over
Crossing over
homologous chromosomes cross over parts of each other to exchange DNA
Metaphase II
chromosomes line up
Anaphase II
sister chromatids separate *like in mitosis
Telophase II & Cytokinesis
4 haploid cells
each daughter cell is genetically unique
Difference between Meiosis I and Meiosis II
Meiosis II is when 2 haploid cells split into four
Sources of Genetic Variation
crossing over
independent assortment
random fertilization
Independent Assortment of Chromosomes
random orientation of homologous pairs in Metaphase I
Random Fertilization
any sperm w/ any egg
What is the purpose of Mitosis and Meiosis
Mitosis: growth and repair
Meiosis: reproduction