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 23 Meiosis 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

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(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 Meiosis First DivisionSecond 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

Second Meiotic 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

U sing 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 pages You will need your textbook tomorrow!!!!!!

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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, the Primary sex cells of the sperm or ova must 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 chromosomes takes place (crossing-over)

NON DISJUNCTION

Part Two: Meiosis II begins

In ALL FOUR CELLS n=2

Meiosis for real !!!!! Meiosis 1 Animation Meiosis 1 Animation (360 kb) Meiosis 2 Animation Meiosis 2 Animation (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

Parthenogenesis but 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

What are some differences between External and Internal Fertilization? Provide examples!!!

External Fertilization

Happy Earth Day

External Fertilization

Internal Fertilization Takes place inside the body of the female Less eggs are required Ex: mammals, birds and reptiles

Internal Fertilization