I. Introduction to Heredity

A. Asexual Reproduction B. Sexual Reproduction

Heredity

Transmission of traits from one generation to the next (inheritance)

Variation

Differences between individuals

Genetics

the study of heredity and hereditary variation

Gametes

Reproductive cells that transmit genes from one generation to the next

Asexual Reproduction

Single parent produces offspring

Unicellular- split

Multicellular budding or fragmentation

Asexual Reproduction in Eukaryotes

Mitotic Division

Mitotic division

1 diploid (2n) parent -> 2 diploid offspring

1 haploid (n) parent -> 2 haploid offspring

Produces clones- offspring genetically identical to parent

Advantages of Asexual Reproduction

Fast

Low E requirement

Safe

Lots of offspring

Well adapted? NO Don't change, low genetic diversity

Sexual Reproduction

Fusion of 2 gametes to form a zygote

Gamete (n) + gamete (n) -> fertilization -> zygote (2n)

Gametes usually different from different parents (but not always)

Offspring not genetically identical to parents nor each other

Costs of sexual reproduction

Slow

High E requirement

Dangerous- predation, disease

Well adapted? Offspring only get half of your genes- genome diffusion

Advantage of sexual reproduction

Genetic variation!!!

Offspring represent novel combinations of parents’ genes

More likely able to survive environmental change or stress

A problem:

If gametes have same number of chromosomes as parents

Chromosomes number double when they fuse

Solution:

Meiosis

Reduction division

Cell divides twice

1 diploid (n) cell -> 4 haploid (n) cells