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Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving! 3. Be sure to get lab report guidelines for last lab report - due in class Dec. 6th. We’ll be much more stringent in grading second lab report; ask questions if unsure.
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Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Jan 04, 2016

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Arlene Mills
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Page 1: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Announcements

1. Mean on multiple choice section of exam 3 = 71%Range from 22% - 100%; 5 people didn’t take exam 3.

2. Reminder - no labs week of Thanksgiving!

3. Be sure to get lab report guidelines for last lab report - due in class Dec. 6th. We’ll be much more stringent in grading second lab report; ask questions if unsure.

Page 2: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

1. First approach to determine whether a behavior has genetic components - examine differences in behavior between closely related organisms

2. Second approach -selection of a preferred behavior from a genetically heterogeneous population; can trait be transferred by genetic crosses?

3. Third approach -A single gene can control a single behavior (but most behaviors are more complex)

4. Genetics of behavior in Drosophila - courtship behavior and the yellow mutation

Review of lecture 33

Page 3: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

I. Genetics of behavior in Drosophila

II. Genetics of human behavior

III. Genetics of behavior in C. elegans

Overview of lecture 34

Page 4: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

I. Some Behavioral Mutants of Drosophila

Page 5: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Scientists Find Warmth May Make Some Flies Gay ReutersNov 15 2002 10:27AM

BERLIN (Reuters) - A leading German magazine reported on Friday that researchers have found a certain type of fly can show homosexual tendencies when temperatures are increased above 86 degrees Fahrenheit. The monthly natural science magazine "Geo" said researchers at the Beckman Research Institute in Los Angeles had found the fruit fly "drosophila melanogaster" had developeda "homosexual preference" when the laboratory temperature was increased from about 19 degrees to above 30 degrees."The male flies displayed clear heterosexual activities when temperatures were at 19 degrees, but above 30 degrees their behavior changed within minutes," the report in the December issue of "Geo" released on Friday said."The male flies ignored the female partners at that point and chased after their male counterparts. As soon as the temperature was reduced again, they returned to theiroriginal behavior."The fruit fly, which is about 3 mm long, typically accumulates around spoiled fruit. It is one of the most valuable organisms in biological research, particularly ingenetics and developmental biology.The scientists that made the discovery were led by ToshihiroKitamoto.

Page 6: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

II. Human Behavioral Mutations

More difficult to characterize genetic control of behavior in humans - why?

Page 7: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Human Behavioral Mutations• Huntington Disease (autosomal dominant)• ** Monamine oxidase syndrome, (mental retardation & aggression),

enzymes degrade neurotransmitters.– Typically hemizygous males (X-linked recessive)

• Lesch-Nyhan syndrome (X-linked recessive)• Tay-Sachs Disease (autosomal recessive)• Phenylketonuria (autosomal recessive)• Down Syndrome (tri-21 or translocation)• ** Schizophrenia

– 1/100– Delusional behavior (- not depression -)– High concordance in monozygotic twins– Polygenic (3-6 genes)– One on human chromosome 22– "A Beautiful Mind", 2002 Best Picture Academy Award

• ** Alzheimer's Disease

Singlegene

Multiplegenes

Page 8: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Pedigree of family with monoamine oxidase syndrome

Using RFLP analysis, locus mapped to X chromosome, near MAOA gene.

Learning check1. In which gene was genetic variation observed that allowed mapping

to X chr.?2. How would you confirm MAOA gene is involved in this syndrome in

this family?

Page 9: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Alzheimer's Disease

• Brain: hippocampal neurons degenerate, short-term memory decreases as does thinking, ability to care for oneself.

• Brain deposits called neuritic plaques and cells have neurofibrillary tangles (best diagnosis on autopsy).

• Over 25% of those over 85 yrs have it.

• Most get the late-onset sporadic form, but some have early-onset inherited form.

Page 10: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Alzheimer's Disease - cont.Genes• Chrom. 21, APP = amyloid precursor protein gene (-> a protease

inhibitor in the membrane)– Incorrect processing -> ~40aa beta-amyloid.– May poison cholinergic neurons– The inherited mutation in some families, but also in many

sporatic cases of Alzheimer's• Chrom. 19, apoE (apolipoprotein E) gene

– Early onset, inherited; also sporatic– The mutation apoE4 product binds tightly to beta-amyloid

• Chrom. 14– Early onset, inherited

• Treatment (none)– April 2002, mice, vaccination w/ beta-amyloid helps– Inhibitors of neurotransmitter acetylcholinesterase delay

symptoms but don't cure.

Page 11: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

III. Genetics of behavior in C. elegans

- chosen by Sydney Brenner (1968) specifically to study behavior

- Has a relatively simple nervous system: of 959 somatic cells, 302 are neurons; entire nervous system has been reconstructed 3-D

- Brenner’s plan was to induce a large number of behavioral mutations (how?) and correlate aberrant behavior with structural and biochemical alterations in the nervous system

-Three behaviors originally characterized:

- positive chemotaxis- thermotaxis - not as much known- generalized movement

Page 12: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Chemotactic response to ammonium chloride

Page 13: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Generalized movement mutations

Of 300 induced mutations, 77 affected movement of animal

What are two movement mutants you’ve seen in lab?

Rollers (rol): go in circles on agar plates- defects in nerve cord or body musculature

Uncoordinated (unc): from twitching to nearly complete paralysis- defects in nerve cord or body musculature- many unc mutants on each of 6 chromosomes

Page 14: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Genetic approach to study feeding behavior

How do worms eat? What do worms eat?

Page 15: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!
Page 16: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Isolate and characterize genes that control presence or absence, function, and patterns of innervation of 20 neurons responsible for feeding behavior.

1. Screen 38,000 progeny of mutagenized worms

2. Assign 52 mutations to 35 genes on all 6 chromosomes

Three phenotypic mutant classes:

eat (41 mutations) - affect nervous system function and muscle functionspha (2 mutations) - defects in morphogenesisphm (9 mutations) - affect muscle contraction

Genetic approach to study feeding behavior

Cloned genes = ion channels and signaling cascades

Avery, 1993

Page 17: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Genetic approach to study chemotaxisPaper by Bargmann et al., 1993. Cell 74: 515-527.

Known at start of study: 1. in vertebrates, olfaction is used to detect presence of any volatile

organic molecule and discriminate among different molecules2. Odorants bind to receptors in cilia of olfactory neurons and induce a

signaling cascade in the cell

Questions: 1. How specific is interaction of odorants and receptors?2. How many receptors are expressed on a single olfactory neuron?

3. How is information about odorants trnsmitted to brain to generate appropriate behavior?

Approach: determine whether C. elegans is attracted to volatile organic molecules; then screen for mutants that fail to chemotax to particular odorant; characterization of mutants will help address questions and allow for genes involved in process to be identified

Page 18: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Results of Bargmann study

- tested 121 volatile organic chemicals: 50 strong attractants, 11 variable, weak attractants; 60 not attractive

Page 19: Announcements 1. Mean on multiple choice section of exam 3 = 71% Range from 22% - 100%; 5 people didn’t take exam 3. 2. Reminder - no labs week of Thanksgiving!

Characterization of odr mutants