Sexual Reproduction and Meiosis

asexual reproduction defintion

Many cells and unicellular organisms reproduce via cell division.

Prokaryotic cells reproduce asexually via

binary fission

Eukaryotic cells reproduce asexually via

the cell cycle and mitosis

Asexual reproduction key factors

• only one parent

• Offspring are clones: genetically identical to each other and parent cell

• rare mutations are the only source of genetic variation

Sexual reproduction key factors

• two parents

• Both parents contribute genetic material to offspring

• offspring have unique combination of genes

• lots of genetic variation, even without mutation

Haploid (n)

A cell with one set of chromosomes. (n)= 23 chromosomes

Diploid (2n)

A cell with two sets of homologous chromosomes. 2(n)= 46 chromosomes

Organisms that reproduce sexually must be able to produce

haploid and diploid cells

Haploid cells arise from

diploid cells via meiosis

Homologous chromosomes (homologs)

chromosomes with the same genes in the same order. one homolog inherited from each parent

paternal c’ some 1: A-B-C-D-E-F……M-N

maternal c’ some 1: A-B-C-D-E-F…...M-N

Homologous chromosomes

Non-homologous chromosomes

carry different sets of genes

c’ some 1: A-B-C-D-E-F…..M-N

c’ some 2: O-P-Q-R…….Y-Z

Non-homologous chromosomes

alleles

Different versions of the same gene

Karyotype

Preparation of metaphase chromosomes viewed under the microscope

autosomes

chromosomes 1 through 22

sex chromosomes

X & Y

only haploid cells: don’t divide following meiosis

gametes

Male gamete

sperm

Female gamete

egg

special cells that produce gametes

germ cells

all other cells

somatic cells