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Transcript of Using the worksheet received today complete the first page. Use your HW to Label the steps of...
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
ng
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