EQ: How are sexual and asexual reproduction alike and different? Reproducing a Species EQ: How are sexual and asexual reproduction alike and different?

Two Kinds of Reproduction Asexual Sexual Mitosis Only one parent cell is needed Division results in offspring genetically identical to the parents Regeneration (starfish, worms) Uniform offspring Large numbers offspring produced quickly Meiosis Two parent cells join Sex cells Sperm= males Eggs = females Offspring share traits with traits with their parents, but are not exactly like their parents Diverse offspring Longer period of time for offspring production Added from Meiosis 2014

Meiosis In 1903, an American graduate student named Walter Sutton made an important observation. While studying grasshopper cells, Sutton observed that chromosomes occurred in distinct pairs And that during meiosis, the chromosome pairs split, and each chromosome goes to its own cell.

Meiosis While mitosis was cell division for growth, meiosis is cell division for sexual reproduction. Meiosis happens when it’s time to reproduce an organism Added from Meiosis 2014

The Big Idea There are TWO cell divisions Mitosis has one division, but meiosis has TWO You still have to remember PMATI, but you have to go though it twice Prophase-Metaphase-Anaphase-Telophase-Interphase Four cells are created from one. Start with one, get four! Each cell has only HALF the amount of DNA needed by a cell

The Big Idea The steps are very simple, when you break it down, it’s just two PMATIs in a row. Scientists call it Meiosis I and Meiosis II, but it’s just two PMATIs The interphase that happens between the two PMATIs is very short and the DNA is not replicated The resulting cells (sperm and eggs) have half the number of chromosomes (23 in humans) and are referred to as haploid cells. This is basically like the PMATI of regular mitosis.

Meiosis I --- Almost like mitosis Pairs of chromosomes line up at the center of the cell and then are pulled to each side. The genetic material duplicates, the cell divides and two cells result

A Short Interphase Normally, the cell would go about its business of living during its interphase, and slowly duplicate its chromosomes getting ready for its next mitotic division But since this is meiosis, there is a very short interphase and division begins again!

Meiosis II is a bit different from mitosis.. During Prophase II, a process called crossing-over occurs. This crossing over is an exchange of genes. This leads to the genes being mixed up, and the cell is not an exact duplicate like in mitosis The rest of the steps (Metaphase, Anaphase, Telophase) follow the patterns of mitosis and meiosis I, but instead of starting with one cell and ending with two, one cell becomes four!

The Big Idea Instead of two new cells being created with equal numbers of chromosomes like mitosis, the cell divides a second time after the first. Genetic material is mixed up, and different eggs/sperm from the same person have different genetic make up The resulting cells (sperm and eggs) have half the number of chromosomes of a normal (diploid) body cell Haploid cells When a sperm fertilizes an egg, the resulting zygote (fertilized egg) receives one copy of each gene from the mother and one copy from the father. Thus, each person receives half of his/her genes from mom and the other half from dad. Heredity All About You – slide 8 chromosome defintion

Genes and Chromosomes Walter Sutton used his observations of meiosis, and his understanding of the work of another scientist named Gregor Mendel which stated that an offspring receives half its genetic information from its father and the other half from its mother, And some creative thinking, Sutton proposed something very important: Genes are located on chromosomes

Genes and Chromosomes Through his work, Sutton was able to show that the steps of meiosis explained the results of a scientist named Gregor Mendel’s experiments with pea plants. Meiosis explained how characteristics were inherited.

Genes and Chromosomes Information on chromosomes determines many of our traits. Sex chromosomes carry the genes that determine gender

Genes and Chromosomes Sex chromosomes are described as either “X” or “Y” In humans, females have the genotype of XX Males have the genotype of XY

Genes and Chromosomes So how was your gender determined? During meiosis, only one of each of the chromosome pairs ends up in a sex cell. All female sex cells (eggs) have one “X” chromosome However, male sex cells (sperm), will have either an “X” or “Y”

Genes and Chromosomes If an egg is fertilized by a sperm with an “X” chromosome, the offspring will be a female Genotype: XX Girls are X-cellent!!! If the egg is fertilized by a sperm with a “Y” chromosome, the offspring will be a male Genotype XY

Genes and Chromosomes The Y chromosome does not carry all of the genes an X chromosome Males only have one copy of the X chromosome Females have two X chromosomes, so they carry two copies of each gene carried on the X chromosome. This makes a backup gene available if one becomes damaged. Males do not have this back up!

Genes and Chromosomes Examples: Color Blindness Hemophilia Baldness The genes for certain disorders are carried on the X chromosome. These disorders are called sex-linked disorders. Because the gene for such disorders is recessive, males are more likely to be affected

Genetic Counseling Many genetic disorders can be traced through a family tree. If a couple is worried that they might pass a disease to their children, they may consult a genetic counselor. These counselors often make use of a diagram called a pedigree, which is a tool for tracing a trait through generations of a family. By making this pedigree, a counselor can often predict if a person is a carrier of a hereditary disease.

Cystic Fibrosis Pedigree

Comparing Asexual and Sexual Reproduction EQ: How are asexual and sexual reproduction alike and different?

It’s a matter of survival … Organisms within a species must reproduce if their species is to survive. There are two types of reproduction: Asexual Reproduction Sexual Reproduction

Two Kinds of Reproduction Asexual Reproduction Sexual Reproduction Mitosis Only one parent cell is needed Division results in offspring genetically identical to the parents Regeneration (starfish, worms) Uniform offspring Large numbers offspring produced quickly Meiosis Two parent cells join Sex cells Sperm= males Eggs = females Offspring share traits with traits with their parents, but are not exactly like their parents Diverse offspring Longer period of time for offspring production

Comparing Asexual and Sexual Reproduction For today’s activity, you will be divided into two groups: New Mexico Whiptails who reproduce asexually Parthenogensis: eggs undergo a chromosome doubling after meiosis and developing into lizards without being fertilized. Collard Lizards who reproduce sexually

Comparing Asexual and Sexual Reproduction The New Mexico Whiptails will work individually Why? What might be an advantage of asexual reproduction

Comparing Asexual and Sexual Reproduction The Collard Lizards will work in pairs Why? What are advantages of sexual reproduction?

Comparing Asexual and Sexual Reproduction In this activity, all New Mexico Whiptails will be given a blue square of paper, and all new offspring will be represented by a blue square of paper. Collard lizards and their offspring will be represented by different colored squares of paper picked randomly from a bowl. How do the papers analogize to real-life?

Comparing Asexual and Sexual Reproduction In this activity, a round will equal one year. Each year, the New Mexico Whiptails will get a blue square and each set of Collard Lizard parents will get a square from chosen randomly from the bowl. Round 1, Year 1 Why do the New Mexico Whiptails offspring look alike? Why are the Collard Lizard offspring varied? Fill in chart Number of organisms before reproduction (both) Number of new offspring (both) Total number of organisms (both) Round 2, Year 2 Round 3, Year 3

Comparing Asexual and Sexual Reproduction PREDATOR ALERT!!! A rattlesnake strikes, kills and consumes one offspring from each New Mexico Whiptail and each set of Collard Lizard parents

Comparing Asexual and Sexual Reproduction Round 4, Year 4 Round 5, Year 5 DISEASE!!! An intestinal parasite is running through the populations of both the New Mexico Whiptails and the Collard Lizards. Half of the New Mexico Whiptails die, and all of the Collard Lizards with the blue squares die as well Round 6, Year 6 Complete questions at the bottom as a group Complete: Advantages/Disadvantages Table collaboratively

Comparing Asexual and Sexual Reproduction

Selective Breeding In selective breeding, organisms with desirable characteristics are mated. Plants and animals are often selectively bred for higher food quality. Dogs, cats and other pets are also commonly bred selectively. http://pbskids.org/dragonflytv/games/game_dogbreeding.html