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Announcements. 1. Genetics-related course offerings for spring 2003: - BIO 324 Cell biology, 3 credits; 3 hours in lecture - BIO 325 Biotechnology, 3 credits; 5 hours in lab -BIO 397 Seminar in Human gene therapy, 1 credit

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Announcements

1. Genetics-related course offerings for spring 2003:

  • - BIO 324 Cell biology, 3 credits; 3 hours in lecture

  • - BIO 325 Biotechnology, 3 credits; 5 hours in lab

  • -BIO 397 Seminar in Human gene therapy, 1 credit

  • -BIO 403 Undergraduate Research, 3-4 credits; needs to be arranged one semester in advance with faculty

  • -BIO 597Q Confocal microscopy, 4 credits

  • -BIO 597Y Techniques in molecular biology, 3 credits; 3 hours in lecture - no lab.

  • -BIO 620G Conservation Genetics, 3 credits; lecture and lab

  • -BIO 629B Eukaryotic Molecular Genetics seminar, 1 credit

    2. Ch 10: problems 1,4,13, 15 - not to turn in


Restriction Digest Lab: Use This Gel!

1 2 3 4 5

Start measuring

from here.

Lanes

1 - Markers

2 - Uncut plasmid

3 - EcoRI cut

4 - DraI cut

5 - EcoRI + DraI

Molecular weight

markers in bp

3 real bands

2 real bands

Supercoiled form runs

faster, nicked form runs

slower than linearized

plasmid.

Bright band is cut;

faint band is uncut


Review of Last Lecture

  • I. Sry and sex determination

  • II. Dosage compensation - different in humans and flies

  • III. Nondisjunction

    • Monosomy

    • Trisomy


Outline of Lecture 18

Polyploidy

Variation in structure/arrangement of chromosomes

- deletion

- duplication

- inversion

- translocation

III. DNA structure and analysis


I. Polyploidy

Hybridization of closely related species; often sterile.

Additional sets identical to parents.


How does polyploidy arise naturally?- DNA is duplicated in S phase but cell doesn’t go into M phase- Generation of Tetraploids Using Colchicine, a Microtubule Inhibitor

Triploids can be created by inhibition of polar body

formation during oogenesis, followed by fertilization.


How is polyploidy relevant to our daily lives?

  • Polyploids are generally bigger than diploids;

  • therefore, in horticulture and agriculture they are useful.

  • Examples: -Bananas and tiger lilly - 3n

    • -coffee, peanuts, McIntosh apples - 4n

    • -strawberry - 8n


Somatic Cell Hybridizationin Plants createsAllopolyploidHybridsAmerican Cotton is natural 13 + 13 hybrid



Deletions and Rejoining

Chromsome breaks

Part is lost - a deletion

Synapsis with a chromosome

with a large intercalary deletion - loop formation.


Duplications and Rejoining

Cytology showed that bar is not due to a gene mutation.

Gene redundancy

Phenotypic variation

Source of genetic variation during evolution

Unequal crossing over


Ohno’s hypothesis on the role of gene duplication in evolution

Question: How do “new” genes arise?

Duplications might allow for major mutation in the extra copy of the gene. Over time, mutations could result in a new function for the duplicated gene - essentially a new gene.

Example: myoglobin and hemoglobin


Inversions evolution

Inversions don’t add or delete genetic info, but can have effects on gamete formation.


Translocations evolution

Robertsonian translocation: most common type in humans

One example:

SRY in an XX “male”


Inheritance of 14/21 Translocation evolution

In Families with Down Syndrome

(Down)


Familial Down Syndrome Patient evolution

with 14/21 Translocation

21 21 14/21 14


Learning check evolution

What types of chromosome mutations are required to change this chromosome into each of the following?

A B  C D E F G

A B A B  C D E F G

a. inversion of A B

b. deletion of A B

c. duplication of A B

A B  E D C F G

a. translocation of C D E

b. inversion of C D E

c. deletion of C D E

O

O


Learning check #2 evolution

A species has 2n = 16 chromosomes. How many chromosomes will be found per cell in each of the following mutants in this species?

Monosomic

Autotriploid

Trisomic

Autotetraploid

15

24

17

32


III. DNA Structure and analysis evolution

What is the genetic material?

Chromosomes contain protein and DNA - which is it?

What must genetic material do?

1. Replication

2. Storage of information

3. Expression of information

4. Variation by mutation - evolution


The Flow of Genetic Information evolution (The Central Dogma)

Trait


Is the Genetic Material Protein or DNA? evolution

  • Many favored proteins until the mid-1940’s.

  • DNA is simple chemically; how could it then hold complex genetic information?

  • Proteins are much more complicated chemically; perhaps they might hold genetic information.


Evidence for DNA as Hereditary Molecule evolution

  • Transformation studies

    • Griffith (1927)

    • Avery, MacLeod and McCarty (1944)

  • Hershey-Chase experiment (1952)

  • Chargaff’s Rules

  • Molecular Studies


Griffith’s Transformation Expt. evolution

Bacteria Used

Living smooth

(virulent)

Living rough

(avirulent)

Killed smooth

Living rough +

killed smooth

Conclusion:

Killed smooth converted

living rough to virulent cells - a

Transforming Principle (some smooth component) is responsible.


Avery, MacLeod, and McCarty Expt: evolution DNA is the “Transforming Principle”


Hershey-Chase Experiment evolution

  • Radioactively labeled DNA and protein:

    • 32P atom is in phosphate molecules in DNA and RNA, only low levels in protein (phosphorylated proteins).

    • 35S atom is in sulfur containing-amino acids (cysteine and methionine), not in DNA, RNA.


Phage Made Radioactive evolution

Non-radioactive medium

+ bacteria


Phage Infect Cells evolution

32P Phage

35S Phage



Reconstitution of Hybrid TMV evolution (Fraenkel-Conrat & Singer)

Strain 1

Strain 2

Hybrid most like TMV, not HR,

therefore RNA is genetic mat’l


Bases and Sugars evolution

pyrimidines

purines

Ribose

sugars


Bases and Sugars in DNA and RNA evolution

  • In DNA: deoxyribose + A, T, G or C

    • dA deoxyadenosine

    • dT deoxythymidine

    • dG deoxyguanosine

    • dC deoxycytidine

  • In RNA: ribose + A, U, G, or C

    • A adenosine

    • U uridine

    • G guanosine

    • C cytidine


Nucleoside = Base + Sugar evolution Nucleotide = Nucleoside + Phosphate

U

dAMP


dNDP’s and dNTP’s: evolution Note Errors in the Text

deoxy

deoxy

deoxy

deoxy

dNTP (dATP)

dNDP (dTDP)


3’ to 5’ Phosphodiester Bonds Make the Sugar-Phosphate Backbone

New Monomers

Add Here

Strand has 5’-PO4

end and 3’-OH end


Chargaff’s Rules Backbone

  • 1949-1953, quantified amounts of each base in DNA from different species.

  • In every species, amount of A = Amount of T, and Amount of G = Amount of C

  • If that’s true, then A + G = C + T

  • The % GC and % AT varied from species to species, but always adds up to 100%.


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