Reproduction & Embryology. Diploid and Haploid Cells.

Reproduction & Embryology

Where do your genes come from?

Diploid and Haploid Cells

Diploid and Haploid CellsHow many chromosomes (represented by lines) are found in the human diploid cell? 46

How many chromosomes are found in the human haploid cell? 23

Notice that the chromosomes in the diploid cell are in pairs. How many pairs of chromosomes are in the diploid cell? 23

How many pairs of chromosomes are in the haploid cell? 0

What do you think the human body needs haploid cells for? Reproduction

Diploid cells, also called somatic cells, are found throughout the body. Haploid cells, also called gametes, are not. Why do you think haploid cells are not found throughout the body? Haploid cells do not have all the DNA and therefore can not function like somatic cells

Diploid and Haploid CellsDiploid Haploid

# of chromosomes 46 23

# of pairs 23 0

Function Maintain life Sexual Reproduction

Location Somatic (throughout body)

Gamete (gonads – reprodcuctive organs)

Homologous Chromosomes

Homologous Chromosomes

Homologous Chromosomes

Notice how the pairs of chromosomes are arranged in this picture. Briefly describe how they are arranged. Chromosomes are lined up from biggest to smallest (except the last pair). Each pair contains one pick (maternal) and blue (paternal) chromosome. The pairs are homologous.

What is special about the last pair of chromosomes? X and Y are the sex chromosomes – they determine the sex of the individual

What do pairs of chromosomes have in common? Each pair is homologous – meaning it is the same size, shape and carries the same genes.

Homologous Chromosomes

Chromosomes that are the same size, shape and carry the same genes

Diploid Haploid

Brain Cell 46

Skin Cell 46

Sperm 23

What are the two types of division shown?   Mitosis and meiosis

Which type of division produces

Diploid cells? Mitosis

Haploid cells? (egg and sperm)  meiosis

Which type of cell division, mitosis or meiosis, do you think is normally used to produce new cells for:

Growing from a baby to an adult mitosis

Healing a wound mitosis

Making egg and sperm meiosis

Different Methods of Division

Mitosis Meiosis

# of chromosomes in parent cell

46 46

# of chromosomes in daughter cell

46 23

# of pairs in parent cell

23 46

# of pairs in daughter cell

23 0

Daughter cells are identical to…

Parent cell and each other

Nothing – they are different from parent and each other

Fertilization

Based on Figure 4, what process creates the egg and sperm? meiosis

Based on Figure 4, what is fertilization? Uniting of the sperm and egg

Fertilization results in a zygote. A zygote is a single cell, yet a baby is millions of cells. What process creates those millions of cells? mitosis

How does meiosis and fertilization creates unique individuals?

Meiosis creates unique sperm and eggs

Fertilization randomly combines them

How does meiosis and fertilization ensure that the amount of genetic information in the zygote is the same as in each body cell of the parents?

Meiosis creates haploid cells

Fertilization combines two haploid cells

Diploid and Haploid Cells# of Chromosomes # of Pairs

Liver Cell in adult 46 23

Zygote 46 23

Egg 23 0

Sperm 23 0

Brain cell in embryo

46 23

Reproduction & Embryology

Where do your genes come from?

The cell cycle remains the same except…

G1

S

G2

Division: meiosis & cytokinesis

Meiosis instead of Mitosis Occurs

Meiosis is a different way to divide the nucleus – it divides it in half literally – creating nuclei with 23 chromosomes instead of 46!

Prophase IProphase I is the longest and most complex phase.

All of the events that occurred during prophase of mitosis occur +

Homologous chromosomes come together to form a SYNAPSE (TETRAD).

CROSSING-OVER occurs.

Prophase I

Crossing Over

Mixed Up DNA!

Metaphase IHomologous chromosomes line up randomly at the center of the cell. We call this independent assortment.

Metaphase I

Anaphase I

During anaphase the homologous chromosomes in the center of the cell divide.

Telophase I / Cytokinesis

Telophase I two nuclei form and cytokinesis occurs resulting in 2 haploid daughter cells.

Meiosis II

Meiosis II comes directly after cytokinesis. No growth (interphase) takes place.

Meiosis II is broken into 4 events:

prophase II

metaphase II

anaphase II

telophase II.

The steps of Meiosis II are identical to mitosis.

Prophase II

Prophase II is the same as prophase in mitosis.

Metaphase II

Metaphase II is the same as metaphase in mitosis.

Anaphase II

Anaphase II is the same as anaphase in mitosis. Notice that the sister chromatids separate.

Telophase II

Telophase II is the same as telophase in mitosis.

Telophase II

What is the goal of meiosis?

Meiosis 1

Goals – reduce the chromosome number & mix up the DNA

Meiosis 2

Goals – separate sister chromatids and form 4 cells

What 2 important things are accomplished through meiosis 1?

  reduce the chromosome number & mix up the DNA

What 2 important processes help mix up the DNA in meiosis 1?

Crossing over (during prophase I)

Independent Assortment (during Metaphase I) 

What is major difference between metaphase 1 and 2?

Metaphase I – homologous pairs line up

Metaphase II – individual chromosomes line up 

What is the major difference between anaphase 1 and 2?

Anaphase I – homologous chromosomes separate

Anaphase II – sister chromatids separate