Write down and complete the data table below Types of Reproduction AdvantagesDisadvantages Sexual Asexual Allows for genetic variation Can result in better species Requires partner Requires special mechanisms Does not require partner Generally faster Requires fewer steps Does not allow for genetic variation

Through asexual reproduction a clone is produced. Asexual reproduction is usually derived by mitosis.

Parthenogenisis Asexual Reproduction where the female produces offspring from unfertilized eggs.

SEXUAL REPRODUCTION TWO PARENTS GIVING RISE TO AN OFFSPRING THAT IS A GENETIC MIX OF THE PARENTS.

HUMAN LIFE CYCLE The only haploid cells in humans are the gametes.

Angiosperm Life Cycle

Fungi Life Cycle Union of the cytoplasm of the 2 parent mycelia Haploid nuclei contributed by the 2 parents fuse, producing diploid cells

Haploid and diploid cells may undergo mitosis but only diploid cells will undergo meiosis Each cycle of chromosome halving and doubling contributes to genetic variation among offspring THREE TYPES OF LIFE CYCLES

Meiosis A reduction division, followed by fertilization ensures genetic diversity in sexually reproducing organisms

Meiosis Makes gametes Reduces a diploid cell to form multiple haploid cells. – Each haploid cell is genetically different from the other cells. – Each haploid cell contains a mix of half of the genetic information of the parent cell. Meiosis is divided into 2 divisions: – Meiosis I and Meiosis II

Phases of Meiosis Step by step process where a diploid reproductive cell produces 4 haploid daughter cells. First up is Interphase – Same as the cell cycle Cell must divide 2 times in order to produce 4 haploid cells. – The 1 st meiotic division makes 2 cells & then each of these cells divides during the 2 nd meiotic division producing the 4 cells total.

Meiosis 1

Homologous chromosomes They are similar in shape & size and the 2 chromosomes carry the same genes. n represents the number of chromosomes in a haploid cell & 2n for diploid cells.

Prophase I Homologous chromosomes cross over- break & twist around each other; then connect at each other’s initial position =recombinant chromosome Can occur 2 to 3 times between a pair of homologous chromosomes depending on size of chromosomes & position of centromeres

Metaphase I WHAT’S DIFFERENT IN THIS METAPHASE COMPARED TO THE ONE DURING MITOSIS? WHAT DOES INDEPENDENT ASSORTMENT MEAN?

Anaphase I WHAT’S DIFFERENT IN THIS ANAPHASE COMPARED TO THE ONE DURING MITOSIS?

Telophase I AFTER CYTOKINESIS, WILL THESE CELLS BE HAPLOID OR DIPLOID? EXPLAIN

QUICK RE-CAP OF MEIOSIS I Takes place in order to produce two cells with a single set of chromosomes each.

Why don’t the cells go through interphase again before entering prophase II ?

Random Fertilization Adds to genetic variation arising from meiosis – In humans, the fusion of a sperm and egg will produce a zygote with any of about 64 trillion diploid combinations.

WHERE IN MEIOSIS DOES MIXING OF GENETIC INFORMATION OCCUR?

Sometimes chromosomes don’t separate the way they are suppose to = non-disjunction PLAY VIDEO Nondisjunction (Trisomy 21) - An Animated Tutorial

Ex: Down’s Syndrome (aka Trisomy 21 Most common chromosome anomaly. Affects 1 in 800 births Non-disjunction can happen with other chromosomes & all having a major impact on a child’s development

Other non-disjunction disorders Edward’s Syndrome – Trisomy 18 Patau’s Syndrome- Trisomy 13 Turner’s Syndrome- Monsomy X

Karyotypes A photograph of chromosomes found in a cell (during metaphase of mitosis) arranged according to size and shape. The shape depends largely on the location of the centromere. The homologous pairs are place together. These are usually done on unborn fetuses to determine any chromosomal anomalies.

Methods of obtaining cells for karyotyping AmniocentesisChorionic villus sampling

Were these chromosomes taken from a male or female? Is there any non-disjunction? Explain your answers