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Mendelian Genetics

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Alexander Pistell

on 3 April 2014

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Transcript of Mendelian Genetics

Mendelian Genetics
Why do you look like, but not exactly like, your parents?

Why don't you look exactly like your brothers and sisters?

Why do twins look alike, but not exactly alike?

Shows the family history of PHENOTYPES

From a pedigree, determine:

1. Dominant or recessive?

2. autosomal (regular chromosome) or sex-linked (on the X chromosome)?

Phenotype - what shows (appearance)

Genotype - the actual genetic code

Genotype can be

Homo = same
Hetero = different

Genotype vs Phenotype
NO!!!! Environment plays a huge role in gene "expression"

Just like each twin can express her own personality, DNA can
choose whether or not to express certain genes
., and
how often to express those genes.

Think of DNA like a giant recipe book. Depending on your mood, you might choose to cook a certain dish, or one dish over and over.

"Nature vs. Nurture"

Nature = genes
Nurture = environment

Is your intelligence, athletic ability, body shape, and behavior determined 100% by DNA?
Does genotype fully determine phenotype?
Austrian Monk
Studied pea plants - 7 traits - seed shape, flower color, seed coat tint, pod shape, unripe pod color, flower location, and plant height - tested 29,000 pea plants over 7 year period

Pea plants are an awesome genetic MODEL.

Gregor Mendel
Step-by-step guide to Punnett Squares
We can also define evolution as a change in
allele frequencies
in a population

Changes in DNA provide the "variation" in natural selection
; these changes can be either: 1.
or 2.
during the "crossing-over" phase of meiosis (prophase 1)
How does molecular genetics (DNA) connect to evolution?
Do Now
Messenger RNA - genetic message carried from nucleus to cytoplasm
Transfer RNA - transfers amino acids to ribosome
Ribosomal RNA - forms ribosomes
How does a cell use the entire code of DNA's instruction?
Full human DNA code has 46 chromosomes (22 regular pairs and one pair of sex chromosomes)
Each chromosome has many genes
Genes are made up of nucleotides
The Hierarchy of Genetics
Griffith - bacterial "transformation"

Hershey and Chase - Radioactively labeled protein and DNA, to prove that the DNA is passed on through transformation, not protein

Avery - proved DNA was the carrier of genes, instead of proteins

Rosalind Franklin - X-Ray diffraction of DNA hinted at structure

Watson and Crick - double helix discovery

Chargaff - proved that C=G and A=T chemically (same amounts)
The Gradual Discovery of DNA
Point mutation
Frame shift mutation
- Practice on worksheet!

Types of Mutations
PCR - Polymerase chain reaction
Gel electrophoresis
GMO - debate it!
Genetics in Technology
Cause and effect
- Sickle cell anemia
Common Genetic Disorders
3 laws - Law of Segregation, Law of Independent Assortment, Law of Dominance
2. Law of Segregation
3. Law of Independent Assortment
1. Law of Dominance
alleles will mask/hide
- separate genes for separate traits "sort" independently (also because of meiosis)
One out of 2 RANDOM alleles is passed from parent to offspring for each trait
both nucleic acids
Double stranded, deoxyribose sugar, ATCG, more stable
Single stranded, ribose sugar, AUCG (uracil instead of thymine), less stable
The Coca-Cola Analogy for making a protein
DNA in nucleus
amino acids
Master recipe in Coke lair
Copying the recipe in the lair
early recipe
final recipe with cap and bottle
Using the recipe to actually create drink
Chef in the kitchen
Assistant getting ingredients
Finished Coca Cola
The major players:
DNA helicase - unzips DNA
DNA polymerase - creates new DNA strand
DNA Replication
PCR - Polymerase chain reaction
Gel electrophoresis
GMO - debate it!
Genetics in Technology
= The number and appearance of chromosomes
Is this karyotype male or female?
The Strucure of DNA

- Most complex molecule in the universe
- Double helix = twisted ladder

- Cytosine and thymine are pyrimidines
- Adenine and guanine are purines
- Purines have hydrogen bond with pyrimidines

Backbone of alternating sugar (deoxyribose) and phosphate

Nucleotides inside the backbone, hold the two strands together through hydrogen bonding

Ingenious structure -
2 strands, each containing full information, so that it can divide in half and copy (replicate)
More stable because of double strand

Welcome to 8th period!

Mr. Pistell's procedures:

1. After arriving, immediately get started on the do-now. Do-nows will either be collected or graded in your notebook.

2. If you distract other students from learning, you will lose participation points.

3. If you need to use the bathroom, do not interrupt a teacher or fellow student - wait for activity or when I give the class time to think or take notes.

Thank you!

- Mr. Pistell

Inventory of my Traits
Definitions you NEED TO KNOW, from Miller and Levine's glossary:

Genetics - the study of heredity = how characteristics are inherited

Trait - A specific characteristic of an individual (eye color, plant height)

Gene - Sequence of DNA that determines a trait; "factor" that is passed from parent to offspring

Alleles - Different forms of genes
- Homozygous dominant (AA)
- Heterozygous (Aa)
- Homozygous recessive (aa)
1. Draw the big square
2. Divide into 4 smaller squares
3. One parent goes on the left, the other parent goes on the top
4. The two alleles for each parent split.
5. Fill in the boxes - one allele from Mom, one from Dad
6. The genotype is what's inside each little box. The phenotype is what you would see with that genotype.
Do Now - Review (you can use your notes)
Today's Big Question
We all have a set of "instructions", passed down from our parents, that determines our characteristics. How are these instructions passed down from generation to generation?
Review Challenge - Put the following in order, from
Genome (full set of human DNA, all 46 chromosomes)
Nitrogenous base (A, T, C, G)
1. Answer the big question using the words traits, genes, alleles, phenotype, and genotype.

2. write 2 test questions - one multiple choice, one free response
Do Now: My Traits
Determine which version of the 5 traits you have.
Write your results on the top of the worksheet.

1. Are your earlobes attached at the bottom or do they hang free?

2. Smile. Is there a small line (indentation) to the side of your mouth?

3. Clasp your hands together, with fingers interlocked....is your right thumb on top or your left thumb?

4. Can you roll your tongue into a "U" shape (hot dog bun)?

5. What color are your eyes? (simplify to blue, brown, green, black)
Monohybrid vs Dihybrid Cross
Monohybrid - One trait
Dihybrid - 2 traits
Test Cross
If we don't know the genotype of an organism, what genotype should we cross it with, to find out?
1. Based on the Tuesday and today, write a summary of
1. Incomplete dominance
- heterozygous is a blend. Ex: Cross a red and a white flower, you get pink.
2. Codominance
- BOTH alleles are shown at the same time. Ex: Cross a red and a white flower, you get a flower with both red spots and white spots.
3. Pleiotropy

one gene influences many separate phenotypes (albinism)
4. Polygenic inheritance
many genes determine one phenotype/trait (eye color)
Poly = many
Opposite of
monogenic inheritance
- one gene determines one trait (Mendelian)
5. Multiple alleles
More than two alleles (versions of the gene) may determine phenotype
- Human blood
Modern types of inheritance (Non-simple dominance)
Quickfire challenge!
Hold up your index card to vote each round. Last student standing wins!
Why do these twins look different, if they have identical DNA?
1. Write down something new you fully understand.

2. Write down something you need more help with.
Do Now: Draw your family tree, from grandparents to you.
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