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Unit 2 Genetics

Ch 11  The Work of Gregor Mendel

Objectives:

  1. Where does an organism get its unique characteristics?
  2. How are different forms of a gene distributed to offspring?

What would happen if you crossed a tall pea plant with a short pea plant?

tall,  medium, or short

Gregor Mendel was surprised by the result.  He predicted a cross between a purebred tall plant and a short plant would produce medium pea plants.  The results…. the pea plants were ALL TALL

 

Mendel didn’t stop here.  He wanted to know if the trait for short pea plants had “disappeared”.  He crossed two offspring from the original cross.  The results…. tall and short pea plants.

From these crosses, Mendel drew two conlcusions

An individual’s characteristics are determined by factors that are passed from one parental generation to the next.

The Principle of Dominance which states that some some alleles are dominant and other are recessive.  An organism with at least one dominant allele for a trait will exhibit that trait.  In order for an organism to appear recessive, it must have two recessive traits.

11.2 Applying Mendel’s Principles

Objectives

  1. How can we use probability to  predict traits?  Be able to perform single factor crosses determining genotypic and phenotypic ratios and two factor crosses determining phenotypic ratios.
  2. How do alleles segregate when more than one gene is involved?
  3. What did Mendel contribute to genetics?

Vocabulary review:

  • genotype the genetic make up or alleles of an organism  example Tt
  • phenotype the physical characteristics of an organism example Tall pea plant
  • homozygous carrying two of the same alleles for a trait example TT or tt
  • heterozygous carrying two different alleles for a trait example Tt
  • purebred an organism that is homozygous
  • hybred an organism that is heterozygous

In pea plants, tall (T) is dominant to short (t).  In a cross between a homozygous tall plant (TT) with a short plant (tt), all the resulting offspring were tall.

2 factor          The phenotypic ratio  Tall : short        4:0

The genotypic ratio   TT : Tt :  tt           0:  4: 0

 

 

Mendel made in F1 cross by crossing two of the offspring from the above cross.  Predict the results

Tt X Tt

2 factor heter      The phenotypic ratio is  Tall :  Short   _____ : _____

The genotypic ratio is TT :  Tt :  tt  _____  :  _____  :  _____

 

 

Helpful review videos:

Crash course biology # 9

https://www.youtube.com/watch?v=CBezq1fFUEA&index=10&list=PL3EED4C1D684D3ADF

 

11.3 Other Patterns of Inheritance

Objectives:

  1. What are some exceptions to Mendel’s principles?
  2. Does the environment have a role in how genes determine traits?

Vocabulary:

  • Incomplete Dominance –  the heterozygous phenotype lies somewhere between the dominant and recessive condition.

ex RR = Red  WW = White  RW = Pink

  • Codominance – the phenotypes produced by both alleles is clearly expressed.

ex. BB = black  WW = white  BW = black and white

  • Multiple Alleles – many genes exist is many different forms.

ex.  rabbit fur is a single gene that has  at least 4 different alleles

 

Multiple Alleles in Rabbits

Unlike human blood groups where there is co-dominance, rabbits have a hierarchy of dominance among the alleles

Rabbit coat color shows a hierarchy of dominance. Rabbits have four alleles for coat color: C = full color cch = chinchilla ch = Himalayan c = albino

  • C is dominant to cch
  • cch is dominant to ch
  • ch is dominant to c
  • c is recessive to everything

Polygenic traits are produced by interactions by several genes– They are controlled by two or more traits.

Examples:

  • 3 genes code for the reddish color of fruit fly eyes.
  • 4 genes (probably) code for human skin color

How do multiple allele traits differ from polygenic traits?

Can the environment have a role in gene expression?  Examine the data.

Western white butterflies that hatch in the spring have different color patterns than those that hatch in the summer.  Those that hatch in the spring have a darker pattern

Environmental temperature and butterfly wing color

butterfly

  1. What is the difference between the minimum temperature needed to fly and the average spring temp?
  2. Of what advantage is there to darker wing patterns in the spring hatch?
  3. What might be the results of an exceptionally hot spring on wing pigmentation in the western white butterfly?

Review video:

Multiple alleles Blood Types  9:32

mhttps://www.youtube.com/watch?v=rAUTTAFydbg

Co-dominance and multiple alleles 8:36

mhttps://www.youtube.com/watch?v=ejDZN7csuNo

11.4 Meiosis

Objectives:

  1. How many sets of genes are found in most adult organisms?
  2. What events occur during each phase of meiosis?
  3. How is meiosis different from mitosis?
  4. How can two alleles from different genes be inherited together?

 

Meiosis Review Video Links:

Meiosis: Crossing Over and Variability [3D Animation] 6:45

mhttps://www.youtube.com/watch?v=rqPMp0U0HOA

Mr Farrell’s Link

https://prezi.com/aae8qhqjkzwq/meiosis/

A short and sweet review  2:22

https://www.youtube.com/watch?v=4B071d9Ywbc

Craig Savage Science  13:22

http://www.youtube.com/watch?v=iQ22tnDjsh4

Think Well Biology Meiosis Part 1 (5:41) and Part 2 (4:43)

https://www.youtube.com/watch?v=3HWN-rM-O8w

https://www.youtube.com/watch?v=5EevKmfj_Nk

Discovery Channel Square Dance  (3:21)

https://www.youtube.com/watch?v=XROMXTrklmQ

https://www.youtube.com/watch?v=iCL6d0OwKt8

Khan Academy 27:22

https://www.youtube.com/watch?v=ijLc52LmFQg

 

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Chapter 12

Ch 12.1 Identifying the Substances of Genes

Several scientists made contributions to identifying DNA.  Analyze the following experiments to discover how the substance of genes was identified.

Griffith’s Experiment

 

Examine the data table also found on page 339.

Screen Shot 2014-02-18 at 10.26.11 AM

  1. What happened when the S-strain was injected into the mouse?
  2.  What happened when the heat-killed  S-strain was injected into the mouse?
  3.  What do you predict will be the result of the mixture of Heat-killed S strain and live R strain?
  4.  What were the actual results?  Page 339
  5. How could this have happened if the S-strain was heat-killed?
  6. What did Griffith conclude from his experiment?
  7. Define transformation.

 

The Molecular cause of Transformation- Avery’s experiment

Avery’s team repeated Griffin’s transformation experiment.  They wanted to determine the molecule that was important for transformation.

They extracted molecules from heat-killed bacteria and treated them with chemicals that destroyed various types of molecules.  Then, they retested to see if transformation occurred.

 

Examine the table.  What did Avery conclude from the data?

avery

The Hershey-Chase Experiment

Viruses were grown in radioactive isotopes sulfur 35 and phosphorus 32.  Proteins contain almost no phosphorus and DNA contains almost no sulfur.

The tagged viruses were grown with bacteria.

bacteriophage

  1. If protein entered the bacteria, the cells would be filled with __________.
  2. If DNA entered the bacteria, the cells would be filled with __________.
  3.  What filled the cells?
  4. What can you conclude about how DNA is transferred to the bacterial cell?

 

History of the discovery of DNA  14:28

http://www.youtube.com/watch?v=59XnRgnkcB8

Ch 12.2 Structure of DNA  pp. 344-348

Objectives:

  1. What are the chemical components of DNA?
  2. What clues helped scientists solve the structure of DNA?
  3. What does the double helix model tell us about DNA?

 Objective 1:  What are the chemical components of DNA?

DNA is a nucleic acid composed of smaller units called nucleotides.  Each nucleotide is composed of

  1. sugar – deoxyribose
  2. phosphate group
  3. base (A, T, G, or C)

One puzzling fact of DNA is the relationship between its nucleotides.

Objective 2:  What clues helped scientists solve the structure of DNA?

Erwin Chargoff examined the proportion of A, T, G, and C in various organisms.  Examine the data and draw a conclusion about the relative proportions.

Chargraff

  1. What do you notice about the proportions of the bases?  Which bases seem to “match”?
  2. What does that suggest about the relationship among these bases?
  3. If a species has 35 % A, what are the percentages of
  • T = ____ %
  • C= ____ %
  • G= ____ %

Rosalind Franklin (page 346) was an x-ray crystallographer.   Her work focused on using x-rays diffraction photographs of DNA.

Although her picture did not show the structure of DNA, it was a valuable clue and was used by  Watson and Crick to build a model that explained the structure and properties of DNA.

In his book The Double Helix, Watson wrote. “The instant I saw the picture, my mouth fell open and my pulse began to race.”

James Watson and Francis Crick

Clues in Franklin’s x-ray pattern enabled Watson and Crick to build a model that explained the specific structure and specific properties of DNA.

Helpful review videos:

Discovery of DNA’s structure- Rosalind Franklin

http://www.youtube.com/watch?v=VegLVn_1oCE

DNA Structure 10:22

http://www.youtube.com/watch?v=igZdLN7nw6k

Objective 3:  What does the double helix model tell us about DNA?

The double helix model explains Chargaff’s rule of base pairing and how the two strands of DNA are held together.

Antiparallel lines– the two strands of DNA run in opposite directions.  This allows the bases on both strands to come in contact at the center of the molecule.  It also allows each strand of the double helix to carry a sequence of nucleotides- like letters in an alphabet.

analogy- 26 letters compose the many words of the English language

4 bases code for the many materials that make up your body.

Hydrogen boding– the bases on the two strands are held togther by weak hydrogen bonds.

Recall hydrogen bonds are the weak bonds that hold two different water molecules together

Base pairing- Watson and Crick’s model shows that the nitrogen bases must pair specifically-

  • A with T
  • G with C

Their model explains Chargoff’s rule

 

DNA:  Adenine, Guanine, Cytosine, Thymine and complimentary base pairing

http://education-portal.com/academy/lesson/dna-adenine-guanine-cytosine-thymine-complementary-base-pairing.html#lesson

Crash Course Biology:  DNA Structure + Replication

https://www.youtube.com/watch?v=8kK2zwjRV0M&list=PL3EED4C1D684D3ADF&index=11

 

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Chapter 13

13.1 RNA

Objectives:

  1. How does RNA differ from DNA?
  2. How does the cell make RNA?

There are 3 important differences between DNA and RNA

  1. The sugar in RNA is ribose sugar instead of deoxyribose found in DNA
  2. RNA is generally single stranded and not double stranded like DNA
  3. RNA contains the base uracil instead of thymine found in DNA

Most of the work of making RNA comes from transcription.  In transcription, segments of DNA serve as templates to produce a complimentary strand of RNA.

We learned earlier that the double stranded DNA molecule has bases matching up in complimentary pairs:

A-T and G-C

Since RNA has U instead of T :

DNA to RNA

What would be the complimentary RNA strand for the following DNA strand?

A A A  T G C  G C G

 

RNA can be thought of as a disposable copy of DNA.

The main job of RNA is protein synthesis.  There are 3 main types of RNA involved with protein synthesis and each type has its own role in protein synthesis.

  1. mRNA = messenger RNA carries instructions from the DNA to the ribsomes
  2. tRNA = transfer RNA carries each amino acid to the ribsome as coded by the mRNA
  3. rRNA = ribosomal RNA forms the ribosomes where the amino acids are assembled into proteins

 

13.2 Ribosomes and Protein Synthesis

Video review

http://www.youtube.com/watch?v=zwibgNGe4aY

13.3 Mutations

Objectives:

  1. What are mutations?
  2. How do mutations affect genes?

Types of mutations:

The ribosome reads the mRNA codons in groups of three.  Use the analogy of the sentence

“THE CAT ATE THE RAT” to explore the affect the different types of mutations

Point Mutation occurs when there is a change in one base

“THE CAT ATT THE RAT”

Since the ribosome reads the codons in groups of three, 4/5 amino acids would not be affected by this single error.  We will learn later that there may not be an error at all as there are several ways to code for some amino acids

Frameshift mutations

1.  Insertion In an insertion, an extra base is added.  The ribosome still reads the mRNA in groups of 3.

  • “THE CAT ATE THE RAT” becomes “TTH ECA TAT ETH ERA T”

2.  Deletion In a deletion, a base is removed.  The ribosome still reads the mRNA in groups of 3.

  • “THE CAT ATE THE RAT”  becomes “HEC ATA TET HER AT”

 

Which causes a more serious mutation?  Point or Frame Shift.  Explain.

 

Here is a review video:

Point mutation

http://www.youtube.com/watch?v=_tvP6iJEVH0&list=PLD5BBB2BBB6A24674

Frameshift mutation

http://www.youtube.com/watch?v=gQrq3CuPjxs&list=PLD5BBB2BBB6A24674

Chromosomal mutations vs base substitutions

http://www.youtube.com/watch?v=hiRt2uy0dpY

 

Ch 13

 

DNA Fingerprinting

Objectives:

  1. Be able to explain how DNA fingerprinting works
  2. Analyze gels to solve situations

Review videos

Naked Science Scrapbook

http://www.youtube.com/watch?v=ZxWXCT9wVoI

DNA Fingerprinting  :40

http://www.youtube.com/watch?v=EqsqrkvhT88

DNA Fingerprinting:  The movie 2011 6:48

http://www.youtube.com/watch?v=ZEidsjaLSGg

Bozeman Science:  DNA Fingerprinting  Shows how to solve a crime

http://www.youtube.com/watch?v=DbR9xMXuK7c

The ethics of genetic technology

Consider the following quotes:

http://www.notable-quotes.com/g/genetic_engineering_quotes.html

“I not only think that we will tamper with Mother Nature, I think that Mother wants us to”  Willard Gaylan

“Even minor tampering with nature is apt to bring serious consequences, as did the introduction of a single chemical (DDT).  Genetic engineering is tampering on a monumental scale, and nature will surely exact a heavy toll for this trespass.”  Eva Novotny

By mmorrow 7:59 pm