Chapter 13: Meiosis and sexual cycles

The transmission of traits from one generation to the next.

differences that arise from parent to offspring

scientific study of heredity & hereditary variation

inherited from parentcodes for specific proteinresponsible for traits

reproductive cells of sexual reproduction haploid (1/2 of chromosomes)

cells of body except gameteshumans have 46 chromosomes in these

gene's specific location along length of chromosome

single individual is sole parentcopies of all genes to offspringno fusion of gametes

genetically identical individuals

1 gamete each from 2 different parents fuse to form offspring

generation to generation sequence of stages in reproductive history of an organism

homologous chromosomes.

Two chromosomes composing a pair have the same length, centromere position, staining pattern

number and appearance of chromosomes in nucleus of eukaryotic cell

X and Y chromosomes that determine offspring's sex

non-sex determining chromosomes

any cell with 2 sets of chromosomes denoted as 2n, humans 2(23)=46

gametes with single set of chromosomesdenoted as n, humans n=23

fusion of haploid cells' nuclei that produces zygote

haploid cell that results from fertilization

plants & some algae diploid & haploid stages are multicellular.

sporophytemulticellular diploid stage.

spores meiosis in sporphyte produces haploid spores.

gametophyte multicellular haploid stage produced by spore dividing mitotically

cell division that reduces the number of sets of chromosomes from two to one.

reduces chromosome count from diploid to haploid.

Interphase followed by 2 consecutive cell divisionsmeiosis I and meiosis II

4 daughter cells each with only half as many chromosomes as parent

association of sister chromatids all along length

chromosomes condense homologs loosely pair along lengths.

synapsis occurssynaptonemal complex physically connect paired homologs.

crossing over genetic rearrangement between nonsister.

chromatids involves exchange of corresponding DNA segments.

chiasmata exist at point where crossover occurred.

centrosome movement, spindle formation, nuclear envelope breakdown.

proteins attach to kinetochores.

homologs movetoward plate

loci for a gene on a chromosome

different versions of the same gene e.g. coding for eye color

The nuclear membrane breaks apart, chromosomes condense and form homologous chromosomes. Crossing over may occur and cause offspring diversity.

The first of two consecutive cell divisions that produces a cell with half the number of chromosomes as the parent cell

The second consecutive cell division

haploid cells that give rise to multicellular individual without fusing with another cell. divides mitotically to generate a multicellular haploid stage called gametophyte

genetic rearrangement between nonsister.

Homologous pairs line up in center, Spindle fibers attach to the chromosomes.

Homologus pairs seperate and move to opposite ends of the cell.

Nuclear membrane forms around each set of chromosomes, the cytoplasm divides, forming two new daughter cells

Nuclear membrane breaks apart.

Sister chromatids line up along the middle of the cell.

Sister chromatids separate and are pulled to the opposite end of the cells.

Chromosomes are single stranded, end up with four new cells, cells are Haploid, nucleus does reappear.

Individual chromosomes that carry genes derived from two different parents

the multicellular diploid stage of the alternation of generations. goes through meiosis to produce spores

criss crossed regions where crossing over has occured.

alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis. The haploid gametes unite and develop into sporophyte