Cells and Genetics

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Cells and Genetics

• 7th grade Science Standard 7-2

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Teacher note

• Consider doing the plant vs. animal cell drawing
  activity before covering these notes great way
  to see what the kids already know!
• The directions and rubric are in the folder with
  this presentation in a WORD document.

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CELLS

• Cell - The smallest unit of life that conducts
  all life functions.
• Cells vary in size, but contain many of the same
  major parts
• Parts of the cell are called organelles

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Many of the organelles found in a cell
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Parts of the cell

• Cell membrane - the outside covering of a cell.
  It controls what comes in and out of a cell
• Cytoplasm - the gel-like fluid inside of a cell.
  The other organelles are embedded in the
  cytoplasm
• Nucleus - contains DNA and is the control center
  of the cell
• Vacuole(s) - act as storage centers

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• Chloroplasts - the food-making structures of a
  plant cell
• Mitochondria - use oxygen to release energy from
  food. It is sometimes called the powerhouse of
  the cell.
• Cell wall - provides extra support and shape for
  plant cells. It is made mostly of cellulose.

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Plant vs. Animal Cells

• The Difference Between Plant and Animal Cells
• Structures that are common to plant and animal
  cells are the cell membrane, nucleus,
  mitochondria and vacuoles.
• Structures that are specific to plants are the
  cell wall and chloroplasts.

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Animal Cell Plant Cell
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Major structural differences between a plant and
an animal cell include

• Plant cells have a cell wall, but animal cells do
  not. Cell walls provide support and give shape
  to plants.
• Plant cells have chloroplasts, but animal cells
  do not. Chloroplasts enable plants to perform
  photosynthesis to make food.
• Plants cells usually have one or more large
  vacuole(s), while animal cells have smaller
  vacuoles, if any are present. Large vacuoles
  help provide shape and allow the plant to store
  water and food for future use.

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Bacteria Info not found in standards but
important for understanding. You may want to add

• Bacteria are single-celled living organisms in
  the Eubacteria Kingdom. Ancient bacteria belong
  to the Archeabacteria Kingdom
• Bacteria are important. They aid in digestion,
  decompose dead organisms, and are used to make
  many products such as yogurt and cheese.
• Bacteria can also make you very sick with
  diseases such as botulism and tonsillitis.

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Bacteria are classified by their shape.

• 3 basic bacterial shapes
• Round ? Round bacteria are referred to as cocci
• Rod shaped Rod shaped bacteria are known as
  bacilli
• Spiral Spiral shaped bacteria are corkscrew
  shaped are known as spirilla

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Kingdom Protista

• All protists have
• a nucleus with a nuclear membrane
• are usually one-celled.
• live in moist environments

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Protists are grouped by the way they move and
obtain food

• Pseudopods
• Cilia
• Flagella

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Protists with Pseudopods

• Example Amoeba
• Move by extending their bodies forward and then
  pulling the rest of their bodies forward as well.
  
• The finger-like structures that they project
  forward are called pseudopods (false foot). 
• The pseudopods are also used to trap food.

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Protists with Cilia

• Example the paramecium
• Move by beating tiny hair-like structures called
  cilia. 
• The cilia act as tiny oars that allow the protist
  to move through its watery environment.
• The cilia also beat and help to capture food

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Protists with Flagella

• Example the Euglena
• Move by pulling themselves with long whip like
  structure called flagella. 
• Can have one or more flagella that help them
  move.
• Euglena has characteristics of both a plant and
  an animal, it contains chloroplasts that
  photosynthesize and also can consume other
  organisms

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Viruses

• Kingdom or not a Kingdom?
• Viruses are much smaller than bacteria and can
  only be seen with an electron microscope.
• Contains genetic information wrapped in a protein
  coat.
• A virus is an infectious organism that reproduces
  within the cells of an infected host.

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Viruses Cont.

• In isolation, viruses show none of the expected
  signs of life. They do not respond to stimuli,
  they do not grow they do not do any of the
  things we normally associate with life. Strictly
  speaking, they should not be considered as
  "living" organisms at all.

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• However they do show one of the most important
  signs of life the ability to reproduce.
• A virus is not alive until it enters the cells of
  a living plant or animal.

Attach Invade Copy
Release
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Viruses Cont.

• Viruses can be useful as well as harmful.
• Viruses are responsible for causing many diseases
  in living things (for example AIDS in humans).
• Even viruses engineered for useful purposes can
  be harmful if unchecked.

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Cellular Processes Photosynthesis, Respiration,
Diffusion and Mitosis
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Photosynthesis

• Photosynthesis - The life cycle begins with
  photosynthesis within a plant cell.
• The plant, uses the energy from sunlight, carbon
  dioxide, and water, to make food.
• The plant cell then releases oxygen as waste.

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Photosynthesis Cont.

• Once the food is formed it is either used by
  the plant or consumed by an animal.
• This food is broken down in the plant or animals
  cell through a process called respiration.

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Respiration

• Respiration - Breaks food into carbon dioxide,
  water, and energy.
• Carbon dioxide and water are the waste products
  of respiration.
• The cell uses the energy to build, repair, and
  reproduce cells.

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• Elimination - Rids the cells of waste products
  that would be toxic to the cell.
• Diffusion - Molecules move from a crowded area to
  a less crowded area as waste molecules accumulate
  in a cell, the waste will move out of the cell
  and be eliminated.

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• Mitosis- Cell reproduction
• Enables a cell to make an exact copy of itself.
• Results in the production of two daughter cells
  from a single parent cell. daughter cells - are
  identical to one another and to the original
  parent cell.
• Needed for growth, replacement, and asexual
  reproduction.

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GENETICS

• Grade 7 Standard 7-2 Continued

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Genetics and Genes

• Genes - the physical unit of heredity.
• Genes are formed from DNA
• Located on the chromosomes

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Genes Cont.

• Are responsible for the inherited characteristics
  that distinguish one individual from another.
• Each human individual has an estimated 30,000
  separate genes.

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Chromosomes

• Chromosomes - the self-replicating genetic
  structures of cells.

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Inherited Traits

• Inherited traits are those that are passed from
  parent to offspring.
• Examples of inherited traits are eye color, eye
  shape, hair type, or face shape.

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Representing Traits

• We represent gene traits with letters.
• Ex. B black bunny fur
• b white bunny fur

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• Dominant trait - trait that will always be
  expressed.
• Alleles for dominant traits are represented by a
  capital letter. Ex. B

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Inherited Traits

• Recessive trait - trait that will only be
  expressed if two recessive traits have been
  passed.
• Alleles for recessive traits are represented by a
  lowercase letter. Ex. B
• In the presence of a dominant trait, the
  recessive trait will not appear. Ex. Bb

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Inherited Traits

• Phenotype - Physical and behavioral
  characteristics.  Ex. eye color, height, or skin
  color
• Genotype - The genetic makeup of an organism. 
  Ex. BB, Bb, bb
• Genotype represents the collection of all the
  genes found on the chromosomes in the nucleus of
  each cell. These genes are used as a "blueprint"
  or set of instructions for building and
  maintaining a living creature.

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Mechanisms of Inheritance

• Biological information can be passed on from one
  generation to the next.
• Each gene is copied and then the copy is
  transferred to the new cell or organism as it
  reproduces and duplicates itself
• Reproduction is a basic and fundamental process
  common to all forms of life on earth.

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Mechanisms of Inheritance Cont.

• In this process organisms and cells produce new
  copies of themselves by following the
  instructions and blueprints they all carry in the
  genetic code.
• During reproduction these instructions and
  blueprints, in the form of biological
  information, are copied and then passed on from
  one generation to the next. This is inheritance.
  The offspring receives one gene from each parent.

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Mechanisms of Inheritance

• Cellular life depends on the ability of cells to
  grow, copy their biological information, and then
  divide into two new cells, ensuring that each new
  cell receives a complete copy of all the
  information it needs. This is cell division.

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Punnet Squares

• A monohybrid inheritance is the inheritance of a
  single characteristic.
• Ex. Crossing a tall (Tt) plant a short (tt) plant
  
• Every new cell has received one gene from each
  parent
• A cell with Tt genotype has received a gene for
  tall height dominance (T) from one parent and a
  recessive gene for short height from the other
  parent (t).

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Punnet Squares

• Each parent has two genes and the probability
  that the offspring receive one or the other gene
  is determined by a Punnett square.

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Inherited Traits

• Some traits can be influenced by environmental
  factors.
• Inherited traits are passed on from generation to
  generation when chromosomes carrying genes are
  passed from parent to offspring in sex cells.

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Inherited Traits

• Some inherited traits are dominant, some are
  recessive, and some are neither.
• Examples of inherited traits in humans include
  color blindness, baldness, blood type, and skin
  color, the ability to taste certain substances,
  or free or attached ear lobes.

Awesome website on heredity (flash
animation) http//www.genetics.gsk.com/flash_hered
ity_actual.htm
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Environmental Factors

• Any characteristic or behavior that cannot be
  attributed to a genetic value or genes of the
  individual is said to be a result of
  environmental factors.
• Ex. Temperature, diet, medical care, or living
  conditions.
• Environment determines the phenotypic pattern of
  expression.

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This chart illustrates three patterns one might
see when studying the influence of genes and
environment on traits in individuals. Trait A
shows a high sibling correlation, but little
heritability . rait B shows a high heritability
since correlation of trait rises sharply with
degree of genetic similarity. Trait C shows low
heritibility, but also low correlations
generally this means Trait C has a high
nonshared environmental variance. In other words,
the degree to which individuals display Trait C
has little to do with either genes or broadly
predictable environmental factorsroughly, the
outcome approaches random for an individual.
Notice also that even identical twins raised in a
common family rarely show 100 trait correlation,
meaning roughly that neither "nature" nor
"nurture" determines everything about an
individual.