2. Heredity & Reproduction 6th Grade Chapter 4 Review Mrs. Nell

3. Heredity Heredity is the passing on of traits from parents to offspring. In this family tree, traits such as hair color and poor eyesight are passed from generation to generation.

4. DNA Chromosomes contain genes and are made up of DNA. Genes are small sections of chromosomes that determine traits (physical characteristics of an organism). DNA is inside the nucleus of cells and carries the genetic information. This information is passed on from parent to offspring. The scientific name for DNA is deoxyribonucleic acid.

5. Alleles The different forms that a gene may have for a trait are called alleles. For instance, in pea plants flowers may be purple or white. Purple is dominant. Dominance is when one trait covers over or masks another form of the trait. White is recessive. A trait that is hidden or masked if the dominant form of the trait is present is called a recessive trait.

6. Dominant vs. Recessive In humans, brown eye color is the dominant trait, whereas non-brown eye color is the recessive trait.

7. Pure When an organism has two identical alleles for a trait, it is said to be a pure bred (ex- 2 purple flower alleles). When an organism contains different alleles for a trait it is said to be a hybrid (ex- 1 purple and 1 white flower allele).

8. Multiple Alleles & Genes Some traits in organisms, like blood typing, are controlled by more than two alleles. Other traits are controlled by more than one gene (like height, weight, eye, skin, and hair color).

9. Reproduction Reproduction is the process by which organisms make more of their own kind. Asexual reproduction is a method of reproduction in which one organism produces a new organism. Hydra budding Budding is a form of asexual reproduction when an offspring grows off of the parent organism. Yeast budding

10. Regeneration Regeneration is a form of asexual reproduction when missing parts grow back or a whole organism forms from a piece of the parent organism. Starfish, sponges, and planaria are a few organisms that can regenerate.

11. Sexual Reproduction In sexual reproduction, a new cell is produced when DNA from both parents combine.

12. Embryo An embryo is a fertilized egg that has begun dividing into more cells.

13. Cloning Cloning is the creation of an organism that is an exact genetic copy of another. This means that the DNA is identical to another organism. In 1997 scientists successfully cloned a sheep named Dolly. Dolly was the first cloned mammal. In 2003, a decision was taken to "euthanize" six-year-old Dolly after a veterinary examination showed that she had a progressive lung disease.

14. Benefits of Cloning Agriculture: Farmers and ranchers can have their strongest crops and animals twinned so that they are less likely to contract diseases. Transplants: Pig hearts are often used as transplants to replace diseased human hearts. Knowledge of Cells: Learning how cells become specialized could benefit people with diseases such as diabetes or could help those with spinal cord injuries walk again.

15. Cloning Today Since Dolly’s creation, scientists have cloned many other mammal species -- cattle, pigs, cats, rabbits, dogs, and even horses. Still, researchers are far from mastering the cloning process. Attempts to clone animals have resulted in numerous losses and abnormalities. More study, experimentation, and technological advancements are needed. The female foal, dubbed Prometea, is actually a clone of the mare that gave birth to it.

16. Cell Division All cell division is not the same. Cells can divide by mitosis, so each daughter cell retains a full set of chromosomes, or by meiosis, which halves the chromosomes and produces sperm and eggs.

17. Mitosis Mitosis is the process when the nuclei of body cells split. This produces two nuclei with the exact same information.

18. Mitosis (Stage 1: Prophase) Chromosomes become visible Nuclear membrane breaks down Spindle fibers form at opposite "poles" of the cell

19. Mitosis (Stage 2: Metaphase) The nuclear membrane disappears completely Chromosomes line up near the center of the cell

20. Mitosis (Stage 3: Anaphase) Paired chromosomes separate and move to opposite ends (poles) of the cell

21. Mitosis (Stage 4: Telophase) Two separate groups of chromosomes at each pole A nuclear membrane begins to form around each set of chromosomes to form two nuclei

22. Meiosis Meiosis is the process of sex cell formation. Eggs are female sex cells and sperm are male sex cells. Fertilization is the process in which sperm and egg unite, resulting in a new individual with a full set of chromosomes.

23. Genetics Genetics is the study of how traits are passed from parent to offspring. Individual animals and plants differ from other individuals of the same species in all sorts of ways, even when they are offspring of the same parents. These differences between individuals of the same species are called variations. Height is a variation

24. Mutations Sometimes genes change by mutation- a random mistake during the copying of genetic material in meiosis or mitosis. Mutations can also occur due to environmental factors (X-rays, dangerous chemicals, etc.). Mutations are the source of all genetic variation and therefore the basis of evolutionary change. Down's syndrome is caused by the presence of an extra chromosome in chromosome set 21.

25. Gene Mutations In gene mutations a chemical change occurs in an individual gene. Although this change may be very small, it can cause abnormalities such as albinism.

26. Are you ready for your test???