PCB 3063 General Genetics
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PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics PowerPoint PPT Presentation


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PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics. Number of different chromosomes in a species: n = haploid number. Most eukaryotes have two of each of its different types of chromosome in each of its cells. Thus, they have 2 n chromosomes per cell.

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PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics

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Pcb 3063 general genetics lecture topic 3 chromosome mechanics

PCB 3063 General Genetics

Lecture Topic 3: Chromosome Mechanics


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

Number of different chromosomes in a species:

n = haploid number

Most eukaryotes have two of each of its different types of chromosome in each of its cells.

Thus, they have 2n chromosomes per cell.

2n is its diploid number

Klug, Cummings, and Spencer, 8th ed.


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

centromere

homologous chromosomes

metacentric

acrocentric

telocentric

non-homologous chromosomes

Human Mitotic ChromosomesFigure 2-4 Klug, Cummings, and Spencer, 8th edition


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

more mitotic divisions plus

growth and differentiation

1n

fusion

of gametes

mitosis

2n

meiosis of specialized germ cells

mitosis

2n

2n

2n

2n

fertilized egg

2n

2n

fertilized egg

1n

2n

mature (?) human

with trillions of diploid cells,

each derived by mitosis from

original fertilized egg

gametes

interphase mitosis

G1 S G2 M

cytokinesis

The Human Life Cycle


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

Mitosis of a Cell with a Diploid Number of 4

Fig. 2-8 Klug and Cummings, 7th edition Similar to Fig. 2-7, 8th edition


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

MEIOSIS

Diploid to haploid state

Single round replication followed by two cell divisions

Meiosis I and Meiosis II


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

The Stages of Meiotic Prophase I

Fig. 2-13 Klug and Cummings, 7th edition Similar to Fig. 2-9 Klug, Cummings, and Spencer, 8th edition

early prophase I

mid prophase I

late prophase I


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

The Synaptonemal Complex

Fig. 2-14 Klug, Cummings, and Spencer, 8th edition


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

Completion of Meiosis

Fig. 2-14 Klug and Cummings, 7th edition Similar to Fig. 2-10 Klug, Cummings, and Spencer, 8th ed.

paired chromosomes lined up at metaphase plate

separation of homologues – reductional division

products of meiosis I already haploid – count centromeres!

sister chromatids separate

4 haploid products


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

interphase (G1)

b

b

early prophase I

a

a

B

B

a

A

b

late prophase I

B

B

a

A

a

A

metaphase I

b

b

B

a

B

b

A

b

B

b

b

B

b

A

B

A

A

A

a

A

b

A

A

a

a

anaphase I

b

b

A

A

A

A

a

a

metaphase II

B

B

B

B

b

b

final products

B

B

a

a

a

a

independent assortment

segregation


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

Gametogenesis

Fig. 2-15 Klug and Cummings, 7th edition Similar to Fig. 2-11 Klug, Cummings, and Spencer, 8th edition

diplonema of prophase I

ovulation penetration


Pcb 3063 general genetics lecture topic 3 chromosome mechanics

A Homologous Pair of Lampbrush Chromosomes from the Newt

Alberts et al., Molecular Biology of the Cell, 3rd edition


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