Chapter 13: Meiosis Flashcards
Genes
Hereditary units
Gametes
Reproductive cells that transfer genes
Somatic cells
Body cells excluding reproductive cells
Asexual reproduction
Single individual passes on exact copies of its genome
Clone
Genetically identical individuals; formed through sexual reproduction
Sexual reproduction
Two parents make offspring with unique combinations of their genes
Locus
Gene’s specific location along chromosoke
Karyotype
Ordered display of an organisms chromosomes
Homologous chromosomes
Homologs. Chromosomes of a pair with the same length, centromere position, staining pattern. Control the same inherited characters
Sexx chromosomes
X and Y chromosomes
Autosomes
All of the chromosomes except the sex chromosomes
n
Number of chromosomes in a single set of chromosomes
Diploid cells
Have 2n chromosomes (number of chromosomes in somatic cells)
Haploid cell
Have n chromosomes. (Gametes).
Fertilization
Union of gametes
Zygote
Fertilized egg formed from fused gametes
Germ cells
Specialized cells in the gonads that make gametes
Alteration of generations
Life cycle in plants and some algae with multicellular haploid and diploid stages.
1. Meiosis forms haploid (n) spores
2. Spores form gametophyte
3. Gametophyte makes haploid gametes
4. Gametes fertilize and form diploid (2n) zygote
5. Zygote forms sporophyte
Repeat
Sporophyte
Multicellular diploid stage
Gametophyte
Multicellular haploid stage
Protist/fungi life cycle
- Gametes form diploid zygote
- Single cell zygote undergoes meiosis and forms haploid cells
- Haploid cells undergo mitosis to form multicellular/unicellular adult organism
- Haploid cells then undergo mitosis to form gametes
Repeat
Meiosis 1
Homologous chromosomes separate
Meiosis 2
Sister chromatids separate
Prophase 1
Same as mitosis prophase 1 except:
- homologs loosely lined up and connected by cohesins
- DNA of nonsister chromatids broken at specific points
- synapsis occurs
- crossing over and occurs and chiasmata form
Metaphase 1
Homologous chromosomes line up at metaphase plate
Anaphase 1
Sister chromatid cohesion along the arms breaks down, but cohesion at centromere persists. Homologs separate
Metaphase 2
Sister chromatids align at metaphase plate
Anaphase 2
Sister chromatids separate because cohesion at centromeres break down
Synaptonemal complex
Holds Homologs together in prophase 1. Zipper like structure.
Synapsis (crossing over)
When chromosomes are joined by synaptonemal complex.
Crossing over
Broken ends of homologs are joined to non sister chromosome. (ex: Paternal chromatid joined to piece of maternal chromatid). Must occur at least once per chromosome for homologs to stay together as they move towards metaphase plate.
Chiasmata
Points of crossover in homologs. Hold homologs together in meiosis 1 as spindle forms.
Reductional division
Reduces number of chromosome sets. Done by meiosis 1 because chromosome sets decreases from 2n to n.
Equational divison
Number of chromosome sets remain the same. Meiosis 2.
Independent assortment
Maternal/paternal homologs sorted independently of the other pairs. (Results in different combinations of maternal and paternal chromosomes in daughter cells)
Recombinant chromosomes
Chromosomes with genes from different parents
