Law of inheritance
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Law of inheritance Proposed genetic factors. Chromosomal theory Real observation of division of genetic elements. extentions. Mitosis and meiosis Cell cycle. Genetic analysis. Aneuploid Recombination Gene conversion. Evidence that Genes Reside in the Nucleus.

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Law of inheritance Proposed genetic factors

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Law of inheritance proposed genetic factors

Law of inheritance

Proposed genetic factors

Chromosomal theory

Real observation of division of genetic elements

extentions

Mitosis and meiosis

Cell cycle

Genetic analysis

Aneuploid

Recombination

Gene conversion


Evidence that genes reside in the nucleus

Evidence that Genes Reside in the Nucleus

  • 1667 – Anton van Leeuwenhoek

    • Microscopist

    • Semen contains spermatozoa (sperm animals)

    • Hypothesized that sperm enter egg to achieve fertilization

  • 1854-1874 – confirmation of fertilization through union of eggs and sperm

    • Recorded frog and sea urchin fertilization using microscopy and time-lapse drawings and micrographs


Evidence that genes reside in chromosomes

Evidence that Genes Reside in Chromosomes

  • 1880s – innovations in microscopy and staining techniques identified thread-like structures

  • Provided a means to follow movement of chromosomes during cell division

  • Mitosis – two daughter cells contained same number of chromosomes as parent cell (somatic cells)

  • Meiosis – daughter cells contained half the number of chromosomes as the parents (sperm and eggs)


Law of inheritance proposed genetic factors

Chromosomal theory

Pangenesis

A gradual process

Key observation

1883 E. van Beneden

Hippocrates (460-350 BC)

19th century

The egg and sperm contributes equal number of chromosomes to the fertilized egg


Law of inheritance proposed genetic factors

Boveri

Centriols of ascaris


Law of inheritance proposed genetic factors

Reproduction as the basis of heredity

Cells – prokaryotes, eukaryotes ( with membrane-bound organelles)

Chromosomes

Mitosis (mitox-thread)– cell cycle, cell division

Meiosis (meiwsix-reduction) – oogenesis and spermatogenesis

- meiosis in plants

Life cycle

Principle of Genetics Chapter 2

Cell 112:423-440 2003


Law of inheritance proposed genetic factors

DNA

Deviding E.coli

An interphase eukaryotic cells


Law of inheritance proposed genetic factors

Cell division

*proper distribution of genetic materials into daughter cells

- separation of chromosomes

  • Chromosomes

  • Transmission of genetic materials

  • orderly releases of genetic information ( gene regulation)

The structure of replicated chromosome


Law of inheritance proposed genetic factors

order

cell mass

Duplication of genetic material

Division for equal distribution of genetic material

The cell cycle ( mammalian cells in tissue culture)


Law of inheritance proposed genetic factors

The mitotic spindle in a cultured animal cell

Centrosome

(MTOC)

asters

Centriols

(surrounded by pericentriolar material –initiation of formation of the microtubules)


Law of inheritance proposed genetic factors

Time

Events

Coordination

Mitosis

cytokinesis

Identical daughter cells

Parental cells

2n

2n

Daughter cells


Law of inheritance proposed genetic factors

Three-Dimensional Maps of All Chromosomes in Human Male Fibroblast Nuclei and Prometaphase Rosettes

(PLoS Biol. 2005 May;3(5):e157. Epub 2005 Apr 26. )

chromatin

Chromosome

(condensed)


Law of inheritance proposed genetic factors

cytokinesis

Animal cells A cleavage furrow

Plant cells: Formation of a cell plate


Law of inheritance proposed genetic factors

Chromosome :

sister chromatid cohesion and separation (cohesin)

chromosomal condensation and decondensation (condensins, topoisomerase II)

Microtubules :

spindle formation (cetrosomes, asters)

Microtubule – chromosome interaction:

kinetochore formation


Law of inheritance proposed genetic factors

Meiosis


Law of inheritance proposed genetic factors

Meiosis

1883 Edouard van Beneden

# of chromosome

Eggs of round worm = ½ somatic cells

Zygonema

Pairing Homologous chromosomes

**synapsis

crossing over

1st meiotic division

- reduction division

(separation of homologous chromosomes)

2nd meiotic division

- equatorial division

(separation of sister chromatid)


Law of inheritance proposed genetic factors

Crossing over

The synaptinemal complex


Law of inheritance proposed genetic factors

chiasmatas

disappearance of synaptal complex

**synapsis

crossing over

chromomeres

towards the center of nucleus


Law of inheritance proposed genetic factors

Chiasmata


Law of inheritance proposed genetic factors

Life cycle – the sequence of events from fertilization to death

a few examples

Neurospora crassa

One gene – one enzyme

1st meiotic division

2nd meiotic division

Ordered meiosis


Law of inheritance proposed genetic factors

Saccharomyces cerevisiae

Easy to grow, easy to manipulate


Law of inheritance proposed genetic factors

Meiosis and mitosis in plants

Meiosis  gametogenesis


Law of inheritance proposed genetic factors

Drosophila melanogaster


Law of inheritance proposed genetic factors

Beyond meiosis

Hormone effect

With meiotic program

Early embryologenesis

Diplotene

diplonema

After puberty

After puberty

1/month

Asymtrical cytokinesis

differentiation

Unequal distribution of cytoplasm

differentiation

nonmotile

spermatogenesis

Oogenesis in female


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