Sexual Life Cycle: alteration of halving and doubling chromosome count in each generation
- In sexual reproduction two parents produce offspring with a unique combination of genes.
- In eu. results in gamete formation
- Increases genetic variation bcuz random mutations can be shuffled between organisms
- Zygote: fertilized egg, diploid
- Brief stage and then mitosis of zygote results in all of your body cells
- Haploid (n): cells with half of the number of chromosomes (ex. n=23)
- Gametes: haploid sperm and egg created thru meiosis and pass on genes; not made by mitosis cuz if they did number of chromosomes would keep doubling
- Gametes receive one allele per trait
- Number of alleles determines how many different types of gametes
- Diploid (2n): cells with two sets of chromosomes (2n=46)
- Somatic Cells: (normal) body cells, that have 46 chromosomes (23 pairs), half from mom half from dad
- Homologous chromosomes(homologs): pair of chromosomes with same size, shape, centromere, and same genes that control
specific inheritance pattern but different versions
- One maternal and other paternal
- Allele: different versions of the same gene controlling a trait caused by mutations→ contribute to overall phenotype
- Organism can only inherit 2 alleles for one trait
- Locus (loci): exact location of a gene on a chromosome
- Tetrad: Made up of two pairs of sister chromatids that have synapsed
- Karyotype: picture showing 23 pairs of chromosomes (usually at metaphase)
- Autosomal pairs (22): all of the genes for normal traits
- Sex chromosomes (23rd): determine sex, XY male and XX female
- Gametes receive one allele per trait
Organism vs Organism:
- Organisms differ in number of chromosome and whether diploid or haploid is dominant
- Animals are mainly diploid because their body cells are somatic and not germline
Fungi Life Cycle: are usually haploid but most form temporary diploid structures for sexual reproduction
- Can’t cut one set of chromosomes in half so they do not have meiosis during haploid
- Plant Life Cycle: both haploid and diploid split equally so there is no dominant stage (multicellular)
- Alternation of generations: one gen is haploid and the next may be diploid, it flips every generation
- Sporophyte: multicellular diploid plant Gametophyte: multicellular haploid
- Gametophyte mitosis directly leads to the formation of gametes
- ex. A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular gametophyte