genetics- the study of heredity heredity- passing of traits from parent to offspring
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Genetics- the study of heredityHeredity- passing
of traits from parent to offspring
Vocab- Silent walk
Around the room there are posters with words. If you know the word place a sticker with your name on it on the board. Write next to the sticker the definition, explanation or significance of the word.
Chromatin Molecules Mitosis Chromosomes Interphase Atoms Cell Cycle
Why Are Cells So Small?
Describe what would happen if the basket ball court was the size of a football field? Or a store is 4 times bigger in size without changing the amount of products in the store.
Cell Size Limitations
Just like a game played on too big a field or a store that has too much space cells have limitations on size to maximize function.
Most cells are smaller than the . at the end of this sentence.
WHY?
Surface Area to Volume Ratio
BECAUSE: Maintain Functions! Surface area is the area covered by a
membrane Volume is the space a cell takes up by the
organelles and cytoplasm What happens to the ratio of SA to V as a
cell increases or decreases? Potato lab
What happened?
If volume increases faster than surface area there is too much space inside to move waste out and food in.
Ex. Diffusion, endocytosis and exocytosis Also cellular communication doesn’t reach
organelles fast enough Example protein signal can’t find ribosome
in time.
The Cell Cycle
Once a cell reaches a certain size it must stop growing or divide.
The Cell Cycle (eukaryotes) 3 phases
Interphase Mitosis Cytokinesis
Cell Cycle
Cell Cycle- Interphase
This is the phase where:*growth occurs*carry out of normal functions*copy of DNA*Prepare for division
3 phases of Interphase
G1- right after division, prepares to replicate DNA
Some cells stay here and that is the end of the cycle
Examples: muscle and nerve cells
3 phases of Interphase
S phase- copy of DNA is made as chromatin (relaxed DNA) condenses into chromosomes to be used for division
3 phases of Interphase
G2- prepares to divide nucleus as it takes inventory
Proteins to make microtubles is synthesized in the ribosomes
Cell Cycle- Stage 2Mitosis
Nuclear material divides to separate ends of the cell
New cell is formed after cytokinesis
Mitosis and CytokinesisThe Details!
Stem Cells stemKnow Want to Know Learned
How does Mitosis Relate?
Read page 258 (Biology and Society) With a partner answer the following: 1. How can stem cells be used? 2. Describe how stem cells aid in curing
paralysis. 3. Do you agree or disagree with the use
of stem cells? Why or why not?
How does Mitosis relate? Stage 2 of Cell Cycle
Mitosis is the replication of a cell making an exact copy of the original. How does this relate to stem cells?
What are the stages of Mitosis?
IPMAT
I- interphase 1st part of cell cycle Mitosis moves to PMAT P- prophase Location: nucleus and poles of cell Purpose: condense chromatin into
chromosomes, form spindle between poles, nucleolus disappears, centrioles in animals move to poles, attach spindle to sister chromatinds.
What is a chromosome?
Chromosomes are the condensed version of all genetic information.
M
M- metaphase Location: spindle fibers in middle of cell Purpose: motor proteins pull sister
chromatids to middle (equator) of the cell on the spindle apparatus. Short lived process.
A
A- anaphase Location: spindle fibers Purpose: sister chromatids are separated
T
T- Telophase Location: poles or opposite ends of cell Purpose: sister chromatids arrive at poles
and start to relax and decondense as the nucleolus reforms
What has happened?
What does mitosis accomplish? Are we done yet?
Nope ….Gotta Split!
Last stage of the cell cycle Cytokinesis- division of cells
Animals Plants ProkaryotesUse microfilaments to pinch cytoplasm in half forming 2 new cells –exact copies
Form a cell plate with no pinching of cytoplasm to make a rigid layer
fission
Who’s in charge of this?
What regulates this process? When does it know to start? Finish? Answer: Proteins and enzymes!!!! Like a key
signals a car to start. Each key is set for a specific car. Most cells know if something is wrong and will self destroy or will kill cells not needed: APOPTOSIS (programmed cell death)
BUT WHAT IF…..
What if a cell that has something wrong with it slips through the cracks?
Cancer- uncontrolled growth of mutated cells.
Example:
Carcinogens
Carcinogens are cancer causing agents. Examples: Sun exposure, tobacco, drugs,
alcohol, food additives. Articles: nanoparticles your food
Lab: Comparing Sunscreens. Page 255
vocab
Gene Genetics Law of segregation Homologous chromosomes allele Gamete dominant hybrid Haploid recessive Law of indep Assort Fertilization homozygous Diploid heterozygous Meiosis genotype Crossing over phenotype
Inventory of Your Traits
Are you really that special? Trait activity. Graph on large paper.
Gregor Mendel- The Father of Genetics
Austrian monk lived in a monastery in charge of the garden.
Noticed that some plants were tall, some were short, etc. Wanted to find out how 2 tall plants could produce a short plant and vice versa.
Begin experimenting with pea plants Why did pea plants produce the same seeds every generation?
The Work of Gregor Mendel Used pea plants b/c:
Had a lot of traits to study and produced offspring fast also could self pollinate or cross pollinate.
Ori The original pair of plants that were crossed were called the P (parental) generation. One tall and one short.
The offspring of this cross were called the F1 (first filial) generation. Resulted in 2 tall plants.
Offspring from the F1 generation produced the F2 generation. Result in 3 tall and 1 short.Where did the short plant come from???? He repeated with pea types
(green/yellow) and other traits.
Results from Mendel’s Experiment
Principle of Dominance: some alleles are dominant and some are recessive.
If dominant is present, it will mask the recessive allele.
Genes and Alleles Genes: chemical factors that determine a
trait (characteristic). Allele: different forms or ways of
expressing a gene. Ex: AA, Aa, aa
Dominant Allele: the trait that always shows physically and is represented by a CAPITAL letter. Ex: AA or Aa
Recessive Allele: only shows if the dominant allele is not present. Ex: aa
Homozygous (same) vs. Heterozygous (different)
Homozygous or Purebreed: 2 identical alleles. Ex: AA= homozygous dominant
aa= homozygous recessive Heterozygous or Hybrid: 2 different
alleles. Ex: Aa= heterozygous (always dominant)
Phenotype vs. Genotype
Phenotype: physical characteristics of the organism (what it actually looks like). Ex: tall plant or short plant
Genotype: genetic make up of the organism (what the alleles are). Ex: AA, Aa or aa
Probability and Punnett Squares
ProbabililtyThe likelihood that a particular event
will occur. Flip a coin…what is the probablity it will land on
heads? Does your probablility change depending on how many times you flip the coin?
Principles of probability can be used to PREDICT the outcome of genetic crosses.
Probability cannot predit the exact or precise outcome of an event!
What Causes This?
Sexual reproduction: Segregation: the separation of alleles
during gamete formation. All living things reproduce: Sexual crosses genes and causes
variation Asexual no variation because exact copy Meiosis is the key!!!!
Meiosis
Chromosomes carry our characteristics on them called traits
Instructions for those traits are written by the DNA on sections of those chromosomes producing proteins
Genes are the sections. Each chromosome has hundreds of genes
that determine traits
Homologous Chromosomes
The human body cells have 46 chromosomes- 23 from each parent
Together they are called homologous chromosomes.
Haploid and Diploid Cells
How do we maintain the magic # 46? If only mitosis occurs we would always be
the same- no variation. Sexual reproduction produces gametes or
sex cells with information from Mom and Dad that have 23 chromosomes that combine to make the magic #46!
Haploid to Diploid
Different Species??
Haploids vs Diploids
Haploid- half the genetic material from parent
Diploid – the combination of two haploids one from each parent
How does a haploid form? MEIOSIS
MEIOSIS STEPS
Meiosis 1 – IPMAT Meiosis 2 PMAT The same steps as mitosis only twice
Meiosis I
I- Interphase- metabolic process replication DNA and synthesis of proteins
P- Prophase I- replicated chromosomes and form sister chromtids by SNAPSIS so that CROSSING OVER occurs. Spindle forms
crossing over So the copies that made the pair now are
a little different!
Metaphase I
M- sister chromatids line up at equator this time there are two pairs instead of one like mitosis.
Anaphase I
A- the pairs separate 2n goes to n which moves pairs doesn’t split the sisters up like mitosis.
Telophase I
T- homologous chromosomes reach poles with only 1 member of original chromosome represented because of crossing over. Followed by cytokinesis.
Then we do it again!!!
We do the whole thing again without copying DNA during interphase. Now we end up with ½ the information and have formed sperm and egg!
Ready to combine to make a zygote during fertilization.
So now we can predict!
Now that we know how the sex cell is formed we can predict the possibilities of the genotype and phenotype of offspring
Punnett Square
Diagram showing gene combinations that might result from a genetic cross. 1900 Reginald Punnett created.
Monohybrid crosses
Di hybrid crosses
Punnett Square Practice
Creature Lab Practice worksheets
Exceptions to Mendel’s Principles
Mendel’s principles are not laws because some alleles are neither dominant or recessive and many traits are controlled by multiple alleles
Incomplete Dominance
Incomplete Dominance: one allele is not dominant over the other. Offspring results in a mixture of the two colors. Example: Red flower (R) is crossed with
white flower (W) to produce a pink flower (RW).
Codominance
Codominance: both alleles of the genes contribute to the phenotype of the organism. Example: Chicken with black feathers
crossed with white feathered chicken results in speckled chicken with black and white feathers.
Codominance
For example, red cows crossed with white will generate roan cows. Roan refers to cows that have red coats with white blotches.
Multiple Alleles
More than 2 forms of the same gene in a population
Blood type is an example of a common multiple allele trait. 3 different alleles (A, B, & O). Blood Types can be A, B, AB, O
Blood Types
Punnett Square with Blood Types
Blood Type Testing Lab
what is blood typing?
Polygenic Traits
More than one gene contributes to the phenotype. Ex: range of skin color in humans
The current model of skin color is that there are 3 genes that contribute to skin color. So there are 6 total alleles, 3 from the mother and 3 from the father.
Independent Assortment
Genes for 2 different traits do not influence each other’s inheritance- they separate independently of eachother. Ex: seed shape does not influence seed
color.
How are new varieties of plants and animals made?
Selective breeding or Artificial Selection: Making deliberate crosses or matings of organisms so the offspring will have a desired characteristic. Ex: you desire a white flower so you continually
cross the two lightest yellow flowers for years until you get some that are white.
What is Genetic Engineering?
A process of inserting new genetic information into existing cells in order to modify a specific organism for the purpose of changing one of its characteristics. Ex: Flounder fish produces “antifreeze”
protein that prevents ice from forming in its blood. DNA is identified, removed and placed into DNA of strawberry to help it be more resistant to frost.
Video Lesson
Label walk KWL Videofood Opinions? Year long project
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