Molecular GeneticsLSM1102

S/N Lecture Topics Lecture hours

1. (1) Reproduction and Chromosome Transmission (Cellular Division: Mitosis and Meiosis)

8Wu Jinlu (Sem 1 & 2)

(2) Gene Transfer/Mapping in Bacteria & Bacteriophages(3) Chromosome Organization and Structure (4) Recombination and Transposition

Continual Assessment 1 (on Lectures 1-4) (10% of module scores)

2. (5) Molecular structure of DNA and RNA(6) DNA replication

8He Yuehui (Sem 1)(6) DNA replication

(7) Gene transcription and RNA processing(8) Translation of mRNA

Continual Assessment 2 (on Lectures 5-8) (10% of module scores)

He Yuehui (Sem 1)Liou Yih-Cherng (Sem 2)

Continual Assessment 2 (on Lectures 5 8) (10% of module scores)

3. (9) Mendelian genetics + Sex Chromosomes and Sex Linkage(10) Modes of Inheritance and Pedigree Analysis(11) Variations to Mendelian Genetics Penetrance Expressivity

10Chew Fook Tim (Sem 1 & 2)

(11) Variations to Mendelian Genetics, Penetrance, Expressivity, Pleotrophy and Linkage(12) Population Genetics – Mutation and Selection, Fitness, Overdominance(13) Genetic Epidemiology(13) Genetic Epidemiology

Continual Assessment 3 (on Lecture 9 onwards) (10% of module scores)

Laboratory sessionsPractical 1Extraction of genomic DNA from E. coliBasic bacterial genetic manipulation – colony isolation and differential platingg p y p g

Practical 2Agarose gel electrophoresisExtraction of plasmid DNA from E. coliBasic bacterial genetic manipulation – grid plating Dr. Wu JinluPractical 3 Bacterial TransformationBasic bacterial genetic manipulation – replica plating

P ti l 4

Dr. He YuehuiLS Lab 9 @MD4 Level 4

Practical 4Observation of transformation and replica plating resultsSubmission of laboratory reports (for Practicals 1-3) (up to 10% of module scores)

Practical 5Ob ti f D hil ild t d t tObservation of Drosophila wild types and mutantsGenetic Epidemiology – collection of DNA sample, consent and ethics in researchGenetic epidemiology – collection of phenotypes by survey and objective testingTake Home Assignment - on Mendelian Genetics and Molecular Basis of Inheritance

Practical 6Practical 6Hypothesis testing in Mendelian geneticsTake Home Assignment - on Variations to Mendelian Genetics

Practical (Tutorial) 7 + 8Modes of Inheritance and Human Pedigree Analysis

Dr. Chew FTLS Lab 1&2@S1A Level 3Modes of Inheritance and Human Pedigree Analysis

Hardy-Weinberg EquilibriumPopulation Genetics and Genetic Epidemiology (analysis)Take Home Assignment - on Population Genetics

Level 3

d d

Text Book:Genetics - Analysis and Principles, 2nd or 3rd Edition

Robert J. Brooker

ReferenceConcepts of Genetics: Principles of

Reference

Genetics: International Edition, 9/E, ISBN-10:

Principles of Genetics, 4th EditionISBN: 978-0-

0321540980 471-69939-2

L tLecturers:

• Module Coordinator (for both Semesters I and II)• Module Coordinator (for both Semesters I and II)• Dr Chew Fook Tim (Department of Biological Sciences)• Email: dbscft@nus.edu.sg Tel: 6516 1685• Block S3, Level 2, Functional Genomics Laboratories, Room 5Block S3, Level 2, Functional Genomics Laboratories, Room 5

• Dr Wu Jinlu (Department of Biological Sciences) (Sem I and II)• Email: dbswjl@nus.edu.sg Tel: 6516 8476; S1A-2-27

• Dr He Yuehui (Department of Biological Sciences) (Sem I)• Email: dbshy@nus.edu.sg Tel: 6516 2716

• Dr Liou Yuh-Cherng (Department of Biological Sciences) (Sem II)• Email: bchlyc@nus.edu.sg Tel: 6516 7711

Wu JinluWu Jinlu

dbswjl@nus.edu.sgj @ g

Tel: 65168476; S1A-L2-27

Keep yourself informed _ http://ivle.nus.edu.sg/lms/

IDEA?

ChromosomeChromosome1 Separation and Transmission1.Separation and Transmission

(eukaryotes)

2. Separation and Transmission (P k t )(Prokaryotes)

3 O i ti d St t3.Organization and Structure

4 Recombination and Transposition4.Recombination and Transposition

CHAPTER 3

REPRODUCTION ANDREPRODUCTION AND CHROMOSOME TRANSMISSION

Genetics: analysis & principles

Robert J. Brooker

Chromosomes3.1 GENERAL FEATURES OF CHROMOSOMES• Biochemically,

CHROMOSOMESGreek khrōma colour + sōma body

y,chromosomes are composed ofp– DNA, which is

the geneticthe genetic materialProteins which– Proteins, which provide an organizedorganized structure

Eukaryotic Chromosomes Are Inherited in SetsInherited in Sets

• Most eukaryotic species are diploid– Have two sets of chromosomes in somatic cells

• Members of a pair of chromosomes are called homologues– The two homologues form a homologous pair

• The two chromosomes in a homologous pair– Are nearly identical in sizey– Have the same banding pattern and centromere

location– Have the same genessame genes

• But not necessarily the same alleles

Genes, Alleles and Chromosome

Dominant

Recessive

The physical location of a gene on a chromosome is called its locus.

3.2 CELLULAR DIVISION-MITOSIS

G0 phase

Interphase (G1, S, G2)• Chromosomes are

decondenseddecondensed

B th d f thi• By the end of this phase, the chromosomeschromosomes have already replicatedreplicated

• The centrosome• The centrosome divides

http://fig.cox.miami.edu/~cmallery/150/cells/c7x22centrosome.jpg

• Mitosis is subdivided into five phases (PPMAT)phases (PPMAT)–Prophase–Prometaphase

M t h–Metaphase–AnaphaseAnaphase–Telophase

Prophase

• Nuclear envelope dissociates into smaller vesicles

• Centrosomes separate toseparate to opposite poles

• The mitotic spindle apparatus is formed

Prometaphase

• Kinetochore microtubules grow from the two poles

• Spindle fibers interact with the sister

h tidchromatids

• The two kinetochores• The two kinetochores on a pair of sister chromatids are attached to kinetochore MTs onto kinetochore MTs on opposite poles

Metaphase• Pairs of sister

chromatids align gthemselves along a plane called the pmetaphase plate

• Each pair of chromatids ischromatids is attached to both poles by kinetochorepoles by kinetochore microtubules

Anaphase

• The connectionThe connection holding the sister chromatidschromatids together is broken

• Each chromatid, now an individual chromosome, is linked to only onelinked to only one pole

pull

hpush

Bold arrows show the force direction

Telophase and Cytokinesis• Chromosomes

reach theirreach their respective poles and decondenseand decondense

• Nuclear membrane reforms to form tworeforms to form two separate nucleiI t• In most cases, mitosis is quickly f ll d bfollowed by cytokinesis

AnimationAnimationmitosismitosis

http://www.youtube.com/watch?v=VlN7K1-9QB0&feature=related

http://highered.mcgraw-hill.com/sites/0072835125/student_view0/index.html

http://www.youtube.com/watch?v VlN7K1 9QB0&feature related

3.3 MEIOSIS

– Meiosis I and II–Each of these is subdivided into

Prophase• Prophase• Prometaphasep• MetaphaseA h• Anaphase

• Telophasep

Prophase I

• Prophase I is further subdivided into periods known as (LZPDD)–Leptotena (thin and delicate)Leptotena (thin and delicate)

–Zygotena (conjugation)

–Pachytena (thick or fat)

–Diplotena (two fold or double)Diplotena (two fold or double)

–Diakinesis (thin and delicate)

A tetrad

A physical exchange of chromosome pieces

Spindle apparatus completeChromatids attached via ki t h i t b lkinetochore microtubules

Metaphase I• Bivalents are organized

along the metaphase plateP i f i t h tid– Pairs of sister chromatids are aligned in a double row rather than a singlerow, rather than a single row (as in mitosis)

– FurthermoreFurthermore• A pair of sister chromatids

is linked to one of theis linked to one of the poles

• And the homologous pair g pis linked to the opposite pole

Figure 3.13

Figure 3.17Figure 3.17

During metaphase I, the bivalents can

align themeselves in two different waystwo different ways

Independent assortmentof the R/r and Y/y allelesalleles

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Independent assortment refers to the random arrangement of pairs of chromosomes. The diagram below g p gshows four possible arrangements of chromosomes during metaphase 1 from an individual that has 6 total chromosomes Suppose that the pink chromosomes arechromosomes. Suppose that the pink chromosomes are those that the individual inherited from its mother and the blue colored ones were inherited from its father. For each chromosome pair, the chromosome that is on the left (maternal or paternal) is determined randomly. As can be seen, there are several alignment possibilities., g p

Down syndrome

Trisomy

The two pairs of sister chromatids separate from each otherH th ti th t

Sister chromatids reach their respective poles and decondenseN l l f t dHowever, the connection that

holds sister chromatids together does not break

Nuclear envelope reforms to produce two separate nuclei

Meiosis II

Mitosis vs Meiosis_Summary

– Mitosis produces two diploid daughter cells– Mitosis produces two diploid daughter cells– Meiosis produce four haploid daughter cells

– Mitosis produces daughter cells that are genetically identicalgenetically identical

– Meiosis produces daughter cells that are not genetically identicalgenetically identical• The daughter cells contain only one

homologous chromosome from each pairhomologous chromosome from each pair

AnimationAnimation

M i i I & IIMeiosis I & II

http://www.youtube.com/watch?v=D1_-mQS_FZ0&feature=related

http://highered.mcgraw-hill.com/sites/0072835125/student_view0/index.html

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

Can o tell the stage of cells•Can you tell the stage of cells (image in the right hand)

• What do the different colors represent for?

Q: A diploid cell has eight h f t I thchromosomes, four per set. In the

following diagram, what phase of mitosis, meiosis I or meiosis II, is this cell in?

A1: The cell is in metaphase of meiosis II. You can tell because the chromosomes are lined up along the metaphase plate and italong the metaphase plate, and it has only four pairs of sister chromatids. If it were mitosis, the

ll ld h i ht i fcell would have eight pairs of sister chromatids.

Q2: A cell is diploid and contains three chromosomes per set. Draw the arrangement of chromosomes during metaphase of gmitosis, and metaphase I and II of meiosis.

A2:A2:

Critical thinking g/application

Infertility of mules

Mules are the result of a cross between a horse (2n c oss bet ee a o se (= 64) mother and donkey (2n = 62) father

http://www.horsegroomingsupplies.com/horse-forums/attachments/horse-chat/45122-mules-dressagemule.jpg

What we have not touched/knownWhat we have not touched/known

1. Division of intracellular organelles

2. Cell cycle control

3. Mechanics of cell division

44.….

Ordinary bull or incredible hulk _Muscles, Mutations, and Myostatin

3.4 Sex Chromosome/Determination

Humans have 46 chromosomes44 autosomes2 h2 sex chromosomes

Males contain one X andMales contain one X and one Y chromosome

(heterogametic)Females have two X chromosomes

(homogametic)(homogametic)The Y chromosome determines maleness

Figure 3.20 Contains many X-linked genes

Involved in o edantibody production

Y-linked geneNecessary for proper

l d l tFollows a pseudoautosomal male developmentFollows a pseudoautosomal pattern of inheritance

• In some insects,– Males are XO and females are XX

• In other insects (fruit fly, for example)– Males are XY and females are XX

• The Y chromosome does not determines maleness• The Y chromosome does not determines maleness• Rather, it is the ratio between the X chromosomes

and the number of sets of autosomes (X/A)– If X/A = 0.5, the fly becomes a male– If X/A = 1.0, the fly becomes a female– If 0.5 <X/A <1.0, it develops as an intersexIf 0.5 X/A 1.0, it develops as an intersex

3-79

X/A ratio and sex determination

Drosophila MDrosophila M.

Q: Assuming that such a fly would be viable, what would b th f f it fl ith th f ll i h lbe the sex of a fruit fly with the following chromosomal composition

A One X and two sets of autosomesA. One X., and two sets of autosomes

B. Two X., one Y., and two sets of A.

C. Two X, two Y, and four sets of A,

D. Four X, two Y, and four sets of A,

• The sex chromosomes are designated Z and W toThe sex chromosomes are designated Z and W to distinguish them from the X and Y chromosomes of mammals

• Males contain two Z chromosomes – Hence, they are homogametic

• Females have one Z and one W chromosomeFemales have one Z and one W chromosome– Hence, they are heterogametic

3-80and some fish

• Males are known as the dronesMales are known as the drones– They are haploid– Produced from unfertilized eggs

• Females include the worker bees and queen bees– They are diploid– Produced from fertilized eggsProduced from fertilized eggs

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Why does sex exist?Why does sex exist?

http://sciencenow.sciencemag.org/cgi/content/full/2000/1017/3

Inheritance and biogenesis of organellesInheritance and biogenesis of organelles in the secretory pathwayMartin Lowe and Francis A Barr

Th i h it f ll d

Martin Lowe and Francis A. Barr

The inheritance of organelle genes and genomes: patterns and mechanismsJi i XJianping Xu