1 Cells, Genetics, and Heredity Unit A Chapter 1 Mr. Mohammed 6 th Grade

2 How Plant and Animal Cells Differ Unit A Chapter 1 Lesson 1

3 The Discovery of Cells Cells cannot be seen by the naked eye. They are just too small. The 1 st microscopes were built over 350 years ago. An English scientist named Robert Hooke was one of the 1 st people to look at cells. He also made up the name.

4 The Cell Theory There are 3 parts. Cells are the basic building blocks of all living things. All living things are made up of cells. Larger organisms tend to have more cells than smaller ones. The human body has over 10 trillion cells of hundreds of different kinds.

5 The Cell Theory All life activities take place in cells. –Each kind of cell carries out the activities for which it is adapted. New cells are produced by existing cells. –New cells come from other cells. –Organisms grow larger because of new cells. –New cells also replace damaged or worn out cells. –Millions of cells in your body die every second. –Your skin continuously produces new cells as old skin cells die and fall away.

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7 Cell Parts cell membrane- Surrounds the cell and keeps it together; controls the substances passing into and out of the cell cell wall- The stiff outer layer that protects a plant cell and gives it shape Cytoplasm- A watery, jellylike substance that fills a cell and contains the other cell parts

8 Cell Parts Mitochondria- Bean-shaped organelles that break down sugar to produce energy Chloroplast- A kind of organelle in plant cells that contains chlorophyll, which enables the plant to make its own food Vacuole- A storage space in a cell enclosed by a membrane Nucleus- The control center of the cell it directs all the cell's activities

9 Cell Parts Chromosome- Provides instructions for all the activities and traits of the cell and the organism nuclear membrane- A membrane that surrounds the nucleus and controls the materials passing into and out of it

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13 The Nucleus of a Cell The nucleus is the control center of the cell. It contains tiny structures inside called chromosomes. (they look like rods) Chromosomes are made of a protein called DNA. –DNA contains information about every part of an organism. –Some people call DNA “the blueprint of life.” The nucleus sends out its instructions in the form of chemicals. These chemicals are the instructions for specific functions of the cell.

14 –DNA What does DNA stand for? –DeoxyriboNucleic Acid

15 Questions Before the invention of the microscope, why couldn’t scientists learn what living things were made of? –They could not see cells with the naked eye. What are the three parts of the cell theory? –1. All living things are made up of cells. –2. All life activities of living things take place in cells. –3. New cells come only from existing cells.

16 Questions What structures do plant cells have that animal cells do not have? –Cell walls and chloroplasts. Why is the nucleus considered the control center of the cell? –The nucleus contains the chromosomes and DNA for the cell. The DNA provides instructions for the cell to carry out al of its activities.

17 How Cells Reproduce Unit A Chapter 1 Lesson 2

18 Vocabulary Gene- A section of DNA that controls specific cell activities and characteristics of every organism.

19 Vocabulary Mitosis- The process of cell division that produces new body cells with complete sets of chromosomes.

20 Vocabulary Meiosis- The process that forms reproductive cells.

21 How Do Plants and Animals Grow? Most living things begin life as a single cell. That single cell then divides to form new cells. Living things grow bigger and taller as cells keep dividing. Growth usually starts slowly, gets faster, and then slows down or stops. Throughout your life your body cells continue to divide and replace cells that are damaged or worn out.

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23 DNA, The Blueprint of Life The DNA in each cell controls the entire development of an organism. The nucleus of both plant and animals contain chromosomes. Chromosomes occur in pairs. A human has 23 pairs of chromosomes, or 46 chromosomes in all. There are 50,000 genes on these chromosomes.

24 DNA, The Blueprint of Life When body cells divide, the new cells have the same DNA as the original. Almost all your cells have the same DNA in them. –Example: The DNA code that instructs brain deveopment, can also be found in a liver cell. DNA codes are only used when needed.

25 Mitosis

26 Meiosis

27 Variation in Organisms Meiosis creates either a sperm cell (male) or an egg cell (female). Each have half the number of chromosomes of an organism’s body cells. The cell that is formed when female (egg) and male (sperm) reproductive cells join has a complete set of chromosomes. Half from the mother and half from the father. Half the genes come from the mother and the other half of genes from the father.

28 Variation in Organisms The new organism will now have a variation or difference in traits from its parents. Some from the mother and some from the father. Humans have a large variation in traits.

29 Variation in Organisms We have 46 chromosomes and about 50,000 different kinds of genes per chromosome. Leaving us with about 2,300,000 possible combinations. Different color of people’s hair and eyes, fingerprint patterns, blood types, etc.

30 Questions If a cell that has 20 chromosomes undergoes mitosis, how many chromosomes will each of the new cells have? –20 In what way does a cell formed by meiosis differ from a cell formed by mitosis? –A cell formed my meiosis has half the number of chromosomes of the original cell. A cell formed by mitosis has the full number of chromosomes.

31 Questions How does meiosis produce variations? –By randomly distributing the two members of each pair of chromosomes into new cells.

32 How Traits are Inherited Unit A Chapter 1 Lesson 3

33 Vocabulary sexual reproduction- The form of reproduction by the joining of a male reproductive cell and a female reproductive cell.

34 Vocabulary Dominant- A factor that will determine whether a trait is shown. DominantRecessive

35 Vocabulary Recessive- A factor not shown when one of a pair is dominant RecessiveDominant

36 Vocabulary Punnett square- A checkerboard-type diagram used to find the possible combinations of factors in the offspring of two parents.

37 Mendel’s Pea Plants An Austrian Monk named Gregor Mendel was the 1 st person to show how traits are passed from parents to offspring. He observed pea plants. Pea plants have genes for tall and short. And for green and yellow seeds.

38 Dominant and Recessive During Mendel’s time, little was known about inheritance. The most common belief at the time was if you crossed a tall and a short plant together you would get a medium height plant. That was not the case. Mendel said each plant carries 2 factors for each trait that it shows. The offspring carries one trait from each parent.

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