Oct 24, 2016 Asexual Reproduction

Humans have 46 chromosomes in each cell of their body *** Humans have 46 chromosomes in each cell of their body*** (except sex cells which have 23) Sperm and Egg Cells

Asexual Reproduction Formation of a new cell from a single cell Happens through mitosis New cell has the exact same DNA as the parent cell

Produces genetically identical offspring Effective method to quickly produce new cells that are exactly the same as the parent cells

Happens in every cell in the human body, except in the ovaries and testes where sex cells are made (ex: making new skin cells happens by asexual reproduction)

Mitosis Diagram: Cell divides to make 2 identical cells with 46 chromosomes in each

There are different types of asexual reproduction.

Sexual Reproduction Humans use sexual reproduction to make their offspring

In general, less complex organisms produce offspring by asexual reproduction, while more complex organisms produce offspring by sexual reproduction

Sexual Reproduction Formation of a new cell from 2 different parent cells (sperm and egg) New cell is genetically different than the parents Happens by meiosis

4 new cells are made 23 chromosomes in each new cell

DNA in new cells is different than the parent cell DNA

Because the genetic information is combined from 2 different parents, there is a completely new genetic code for the offspring Gives us variation (differences in our characteristics)

This is the reason why we look different than our parents and our siblings Produces unique, non-identical individuals

We have 46 chromosomes in each cell of our body (except for the gametes – sperm & egg) Can be sorted into 23 pairs Each of the 23 pairs has the same information, and we call them homologous pairs

Gametes Specialized sex cells Produced in the female ovaries and male testes in humans Ex: sperm and egg cells

Gametes Have 23 chromosomes Need ½ of the genetic information so that when they combine to form a fertilized egg, they make a new cell with a total of 46 chromosomes Produced by meiosis

Another form of cell division Meiosis Another form of cell division Only used in sexual reproduction Creates gametes with 23 chromosomes in each cell

Makes sure that each gamete has a different combination of chromosomes that were present before meiosis Nuclei of the new individual is not identical to the parents

In order for the new individual to have 46 chromosomes, each gamete must have 23 chromosomes When the egg gets fertilized from the sperm, the 23 chromosomes from the egg connect with the 23 chromosomes from the sperm, to give a total of 46 chromosomes

In mitosis, the chromosome number does not change, but in meiosis, gametes are created that have ½ of the original information

Meiosis Diagram: Cell divides to make special gametes with 23 chromosomes in each