Using the worksheet received today complete the first page.

Use your HW to Label the steps of MEIOSIS, quite

Using the worksheet received today complete the first page.

Use your HW to Label the steps of MEIOSIS, quite

Assessment of Teaching Skills-Performance (ATS-P)

Chapter 23Meiosis and

Sexual Reproduction

Replication

Asexual Reproduction (review)

• Single parent gives rise to new offspring by mitotic cell division

• Each new individual receives a set of chromosomes identical to the parent chromosomes

• No variation of hereditary information

(I) Sexual Reproduction• Two parents give rise to new offspring by

the fusion of nuclear materials from two different cells

• Offspring are not identical to the parent

• Variations exist, which increases the species ability to adapt to the changing environment

(A) Reproductive System• Gonads- specialized organs that

produce gametes a) ovaries - female gonad - produce ova (egg) b) testes - male gonad - produce sperm cell

Draw a Cell: 2n=6

1.AS it carries out Meiosis

2.Provide 2 KEY characteristics for each stage

Gametes

• Sex cells

1. Males – sperm

2. Females – ovum

•BOTH ARE MONOPLOID!!!!!!

Comparison of Ova and Sperm

• Egg cells contain stored food in the form of yolk

• Egg cells are larger than sperm• Sperm are motile, egg cells are not

• BOTH ARE MONOPLOID!!!!!!

(Remember) Diploid

• Contain the full number (set) of chromosomes

• Represented by: 2n

(C) Haploid• Also known as monoploid• Represented by: n• The gametes contain half the number of

chromosomes• Remember, gametes are sex cells that

combine to form new offspring. Therefore gametes are haploid and once they fuse (combine), they form a zygote that is diploid

Homologous Chromosomes

• Pairs of similar chromosomes

• Humans have 46 chromosomes:

22 pairs of homologous chromosomes

1 pair of sex chromosomes

Homologous Chromosomes

2n = 46 n=23 (Sperm/Egg)

Diploid Monoploid

Fertilization

• The fusion of the nuclei of one sperm with one ova (egg) to

produce a zygote

                                                                                   

           The above image is from

(II) Meiosis• Known as Reduction Division• Meiosis is a type of cell

division in which the daughter cell receives only half the number of chromosomes present in the parent cell

23 Pairs of chromosomes of a human cell

• The chromosomes labeled X and Y are the sex chromosomes

• XX = female

• XY = male

Replication

(III) Stages of Meiosis• In meiosis, each cell divides twice: 1. The first stage is very similar to

mitosis 2. The second stage is also like mitosis

with the exception that there is NO replication of chromosomes

Phases of MeiosisFirst Division Second Division

Prophase I

Metaphase I

Anaphase I

Telophase I

Prophase II

Metaphase II

Anaphase II

Telophase II

Meiosis

                                                        

       

Meiosis

23 Pairs of chromosomes of a human cell

• The chromosomes labeled X and Y are the sex chromosomes

• XX = female

• XY = male

Replication

Key

SS = single-stranded

DS = double-stranded

First Meiotic Division

Prophase I

• Replication of SS chromosomes into DS chromosomes

• This is known as synapsis

Metaphase I

• Alignment of the DS chromosomes in the middle of

the cell

Anaphase I

• DS chromosome separates

• This is known as disjunction

Telophase I• Cytokinesis occurs and the nuclear membrane reappears around the nuclei of the two newly formed daughter cells

• At this point, the daughter cells are exact replicas of the parent

cell

SecondMeiotic Division

Prophase II

• Chromosomes DO NOT replicate

Metaphase II

• Same as metaphase I

Anaphase II

• Same as anaphase I

Telophase II

• Both daughter cells undergo cytokinesis forming

four haploid cells

• Therefore: As a result of meiosis,

diploid (2n) cells divide and form

haploid (n) cells which mature into specialized reproductive cells (sperm and egg)

• Each daughter cell contains half the number of chromosomes of the original cell

Using complete sentences, describe what do YOU FEEL are the major goals of MITOSIS and MEIOSIS.

I need to see all of the water quality group, for tomorrow's trip.

Tuesday: Read and outline Tuesday: Read and outline pages 307-315pages 307-315

You will need your textbook You will need your textbook tomorrow!!!!!!tomorrow!!!!!!

                                                                                   

           The above image is from

I’m growi

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23 Pairs of chromosomes of a human cell

• The chromosomes labeled X and Y are the sex chromosomes

• XX = female

• XY = male

2n = 46 n=23

Normal somatic cell Sperm cell

Replication

Meiosis

                                                        

       

Crossing Over

Crossing over

                     

      

Crossing Over With Mr. Rizzo

Crossing Over: Two different strands of DNA exchange information

Recombination: result from crossing over, forms

”recombinate chromatids”

Illustration of crossing-over and recombination during the formation of gametes or meiosis.

In meiosis, thePrimary sex cells of the sperm or ovamust replicate, then reduce the number of chromosomes in half. During the early stages of cell division in meiosis, two chromosomes of a homologous pair may exchange segments in the manner shown above, producing genetic variations in the sex cells.

homologous pair

Meiosis: Stage Meiosis I

Synapsis: like chromosomes match up and align during Meiosis

Meiosis 1

chiasma  The site where the exchange of chromosome segments between homologous chromosomestakes place (crossing-over)

NON DISJUNCTION

Part Two: Meiosis II begins

In ALL FOUR CELLS n=2

Meiosis for real !!!!!

Meiosis 1Animation(360 kb)

Meiosis 2Animation(360 kb)

Meiosis for real !!!!!

(III) Sexual Reproduction

in

Animals

Asexual Reproduction (review)

• Single parent gives rise to new offspring by mitotic cell division

• Each new individual receives a set of chromosomes identical to the parent chromosomes

• No variation of hereditary information

2n = 46 n=23

Normal somatic cell Sperm cell

Replication

(I) Sexual Reproduction• Two parents give rise to new offspring by

the fusion of nuclear materials from two different cells

• Offspring are not identical to the parent

• Variations exist, which increases the species ability to adapt to the changing environment

(A) Reproductive System• Gonads- specialized organs that

produce gametes a) ovaries - female gonad - produce ova (egg) b) testes - male gonad - produce sperm cell

(B) Hermaphrodite

• Contain both male and female reproductive structures

(C) Gametogenesis• Process by which gametes are

produced in the gonads

• Two types:

- Spermatogenesis

- Oogenesis

Oogenesis• The primary oocyte goes

through first meiotic division and the cytoplasm of the cell is divided unequally

• The larger daughter cell is called the secondary oocyte and the smaller daughter cell is called the polar body

• During second meiotic division, 1 mature ovum is produced and 3 polar bodies

Spermatogenesis• Primary spermatocyte

goes through first meiotic division and form two daughter cells of equal size

• Each daughter cell (secondary spermatocyte) goes through the second meiotic division forming four motile sperm cells of equal size

Comparison of Ova and Sperm

• Egg cells contain stored food in the form of yolk

• Egg cells are larger than sperm

• Sperm are motile, egg cells are not

(A) Gametes

• Sex cells

1. Males – sperm

2. Females – ovum

(B) Fertilization

• The fusion of the nuclei of one sperm with one ova (egg) to

produce a zygote

• Sperm (n) + Ovum (n) =2n

• Sperm (23) + Ovum (23) = 46

Parthenogenesis•An embryo develops from an unfertilized egg•typically involves the development of eggs into viable offspring from females without fertilization by sperm..

• Parthenogenesis is no longer only for lower invertebrates, such as aphids, mites and nematode worms--it's also been found in fish, bees, birds and lizards.

the second polar body -- the daughter cell produced along with the egg in the second stage of meiosis -- acts like a sperm and re-enters the egg. Essentially the egg fertilizes itself! As this polar body contains identical genetic material to the egg, having been produced by normal division of an already haploid cell, the resulting diploid cell has only half the genetic diversity of the female's original cells. Thus fewer bands appear in the DNA fingerprint of the offspring.

Parthenogenesis

Parthenogenesisbut wrong!!!!!

Fertilization• Union of a haploid

sperm nucleus with a haploid egg nucleus– This results in a

diploid zygote with the full number of chromosomes

n

n

2n

Fertilization• Union of a haploid

sperm nucleus with a haploid egg nucleus

• This results in a diploid zygote with the full number of chromosomes

Fertilization and the Stages of Mitosis

Two types of Fertilization

External Fertilization

Internal Fertilization

**Parthenogenesis**

External Fertilization

•Eggs are fertilized outside the body of the female

•Large number of eggs are required

•This type of fertilization is found in an aquatic environment

Ex: fish and frogs

External Fertilization

External Fertilization

External Fertilization

External Fertilization

What are some differences between External and Internal Fertilization?

Provide examples!!!

External Fertilization

External Fertilization

Happy Earth Day

External Fertilization

External Fertilization

External Fertilization

Internal Fertilization

• Takes place inside the body of the female

• Less eggs are required

Ex: mammals, birds and reptiles

Internal Fertilization