reproduction & embryology
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Reproduction & Embryology. Where do your genes come from?. Diploid and Haploid Cells. How many chromosomes (represented by lines) are found in the human diploid cell? 46 How many chromosomes are found in the human haploid cell? 23 - PowerPoint PPT PresentationTRANSCRIPT
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? 0What 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 individualWhat 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 meiosisWhich 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? meiosisBased on Figure 4, what is fertilization? Uniting of the sperm and eggFertilization results in a zygote. A zygote is a single cell, yet a baby is millions of cells. What process creates those millions of cells? mitosisHow 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 cellsFertilization 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.
Metaphase IHomologous chromosomes line up randomly at the center of the cell. We call this independent assortment.
Anaphase IDuring 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 IIMeiosis 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 IIProphase II is the same as prophase in mitosis.
Metaphase IIMetaphase II is the same as metaphase in mitosis.
Anaphase IIAnaphase 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 1Goals – reduce the chromosome number & mix up the DNA
Meiosis 2Goals – 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 upMetaphase II – individual chromosomes line up
What is the major difference between anaphase 1 and 2?
Anaphase I – homologous chromosomes separateAnaphase II – sister chromatids separate