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Inheritance - 1 - Coggle Diagram

- - - - the allele that gets expressed in the f1 generation is a dominant allele
        
        eg length of stem - tall or dwarf
        
        T (tall) is the dominant allele
  - - - the allele that is not expressed in the f1 generation
        
        but gets expressed in the f2 generation along with the dominant allele
        
        is a recessive allele
  - - - sum total of all genes that an offspring inherits from its parents with respect to a single or several characters
        
        not visible
  - - - or
        
        any physical or physiological or morphological features that can be inherited and which can be observed
        
        visible
    - - to express the genes, the environment needs to be suitable
        
        eg, if a plant has genes for tall,
        
        but its grown in a small space like bonsai
        
        it'll be really dwarfff
  - - - for a particular character
    - - TT
    - - tt
  - - - eg if a plant is tall, and considered hetero, its genotype is Tt
  - - - eg: rest of generation will be the same
    - - doesn't change over generations
        
        so offspring doesn't change
  - - - but the parents differ from one another with respect to the alternate traits of 2 characters
  - - - and then take f2 purple female and white male
    - - usually used to recover desirable characteristics fm populations
        
        eg high yeils, disease resistance, nutritious fruit
        
        always carried out to bring about improvement the varities of plants
  - - - f1 is crossed with one of its parents
        
        whenever you cross f1 with dominant parent, only dominant is shown
        
        cross f1 with recessive parent, both traits are shown in equal proportions
  - - - f1 hybrid shows dominant, (but hetero or homo? molla)
        
        cross it with double recessive parent homozygous
        
        it is a kind of back cross
        
        to recover a useful or desirable
        
        the f2 generation, if f1 was homozygous dominant
        
        all tall
        
        if it was Tt,
        
        then ratio of tall:short is 1:1
  - - - the genotype and phenotype of the offsprings obtained by crossing (fusion) the male and female gametes can be visualised by constructing a simple square shaped diagram
      - rule - male and female
- - - - study of the causes of variation that occurs among a population closely related species
        
        the study of the mechanism behind
    - - in greek civilisation, they first talked about it
  - - - or
        
        the transfer/transmission of genetic information fm parents to offspring over successive generations
        
        or
        
        the genetic continuity of germinal information from parent to offspring over generations
  - - - eg we resemble our parents - but have some differences
  - - - don't code for genes, but
    - - so are said to be genetically strong
  - - - eg length of stem - tall, dwarf
        
        flower colour
        
        shape of seed
        
        eye colour
        
        skin colour
  - - - specific part of a chromosomes that controls the expression of a character
  - - - affecting the same character
        
        but in 2 alternate ways
- - - - no of chromosomes is reduceed to half (diploid to haploid)
        
        1st is reduction division/ heterotypic division
  - - - coz its highly modified
        
        5 diff stages
        
        Leptotene Stage
        
        lepto - thin threads
        
        nucleus
        
        generally large in size in meiocytes
        
        has diploid no of chromosomes
        
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        chromosomes
        
        coz of condensation
        
        don't appear as chromosomes
        
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        chromomeres
        
        unique feature - bead like appearance
        
        coz of formation of chromomeres
        
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        Zygotene Stage
        
        zygo - join, tene - thread
        
        chromosomes
        
        becomes even more condensed
        
        visibility keeps improving
        
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        synapsis
        
        homologus chromosomes of each parent are attracted to each other
        
        important event - characteristic
        
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        bivalent
        
        after synapsis, called bivalent/ tetrad
        
        maternal and paternal have paired
        
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        synaptonemal
        
        makes it pair up - synaptonemal complex
        
        fibrillar ladder like structures formed at the centromere of each homolgus chromsome
        
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        nucleolus
        
        increases in size, as well as nucleus increasing
        
        centriole
        
        has replicated
        
        moves to opposite poles of the cell
        
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        Pachytene Stage
        
        Chromosomes
        
        becomes even thicker and shorter
        
        intensely stained/ distinct bodies
        
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        Sister Chromatids
        
        2
        
        one set belongs to paternal, one fm maternal
        
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        Tetrad
        
        Crossing over
        
        reciprocal exchange of chromatid segments between the non sister chromatids of a homologus pair of chromosomes
        
        the cross where it forms an X shaped structure is called a chiasma/ chiasmata
        
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        Diplotene Stage
        
        diplo - two, tene - thread
        
        2 threads
        
        Disjunction
        
        forces of attraction will lapse between homologus chromosomes pairs
        
        synaptonemal complex is dissolved
        
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        Terminalization
        
        chromosomes doesn't remain like that, it becomes shortre and shorter
        
        chiasma initially at centre, moves to the end
        
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        Diakinesis
        
        dia - across, kinesis - to move
        
        chromosomes
        
        become shorter and condensed
        
        show up as round and intensely stained and scattered throughout the nucleus
        
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        centriole
        
        already duplicated
        
        centrosome shows formation of spindle fibres
        
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        nuclear membrane
        
        slowly start disappearing
        
        nucleolus and nuclear membrane starts disintegrating (not disappearing, coz it comes back in telophase)
  - - - formation is complete
        
        centrioles have reached opposite poles
        
        and like in metaphase of mitosis, location of chromosomes come and align at the equatorial plate
        
        forming an equatorial plate
        
        centromere and arms are present on the equatorial plate
    - - each chromosomes has 2 chromatid
        
        both attached by a centromere
        
        each centromere of each chromosome by chromosomal fibres to the centriole
        
        its only attached to one spindle fibre, not like in mitosis, where each is split up
        
        forming a metaphase plate/equatorial plate, same thing
        
        imaginary plate structure, chromatids and centromeres are present
  - - - was attached to centriole
        
        now, spindle fibres start to shorten
        
        chromosomes initially paired get pushed to the opposite poles
        
        for the first time, homologus chromosomes separate
        
        maternal go to one side and paternal go to one side
    - - drifting away
      - 1st one - leading to terminalisation
        
        moving of chromosomes to opposite poles
    - - 1 centromere for each chromosomes
        
        2 chromstids, connected to 2 spindles
        
        and divides lengthwise
        
        but here entire chromosomes move to the poles
        
        maternal to one side and paternal to one side
        
        but even though one cell gets all the maternal and one all the paternal
        
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  - - - reached opposite poles
        
        don't need to move any more
        
        undegoes decondensation
        
        forming chromatin threads
    - - and nucleolus
        
        initially disintegrating, by metaphase gone
        
        now it reappears
        
        at end of this phase
        
        2 groups of haploid nuclei on both poles
        
        haploid coz of halved chromosomal number - but not truly haploid coz each one is replicated
    - - division of cytoplasm to form 2 daughter cells
        
        2 types
        
        successive cytokinesis
        
        when at end of every meiotic division, it divides
        
        simultaneous cytokinesis
        
        instead of successive
        
        immediately after telophase 1, cell enters into meiosis 2, without cytokinesis
- - - - condensed
        
        slightly thick, not as thick as before
        
        each chromosomes has 2 chromatids
        
        2 distinct chromatids - they're divergent
        
        directed to the poles
        
        connected by a centromere
    - - and nucleolus
        
        which was reformed start to disintegrate again
    - - centrosome duplicates
        
        shows presence of asters
        
        start moving to opposite poles
  - - - have reached opposite poles
        
        spindle formation is complete
        
        chromosomes are aligned at equatorial plate
        
        like mitosis - 1 centromere, 2 chromatids
        
        each centromere attached to spindle on both sides, like mitosis
        
        aligned at the equatorial plate
      - divergent - point to different poles
  - - - chromatids begin to move away fm each other as daughter chromosomes
        
        also called disjunction - drifting away
    - - anaphase 1 - still together, only homologous pairs were separated
        
        but now dna content is halved
        
        equally important, because true haploidy is acheived in this phase
        
        not double anymore - before, only chromosomal number was halved
  - - - spindle disappears
    - - nucleolus and nuclear membrane reforms
- - - - in reproductive cells
    - - parent cell divides into 2 equal parts
        
        but meiosis is reductional division
        
        no of chromosomes is reduced by half
    - - its complex
        
        has 2 phases
        
        meiosis 1 and 2
        
        like how prophase is long and elaborate
        
        so meiosis is extremely slow - prophase 1 of meiosis 1 is the longest and most elaborate
    - - immediately after fertilisation in haploids
  - - - meiosis 1 and 2
        
        1st division - heterotypic division
        
        homologus chromosomes begin to separate
        
        go into diff daughter cells
        
        in the process, no of chromosomes gets reduced to half
        
        daughter cells formed is not genetically identical
        
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        meiosis 2 - homeotypic division
        
        like mitosis, but with small modifications
        
        like mitosis - one cell divides forming 2 daighter cells
        
        each haploid daughter cell
        
        forming 2 more daughter cells each
        
        1 more item...
  - - - or testes of grasshoppers to study
  - - - when high - meiosis
      - when dna to rna high
        
        mitosis occurs
  - - - meiosis 1 - p1, m1, a1, t1
        
        prophase 1
        
        elaborate, long, slow process
        
        5 stages
        
        leptotene
        
        zygotene
        
        pachytene
        
        diplotene
        
        diakinesis
        
        metaphase 1
- - - - resulting in formation of 2 daughter cells
        
        purpose: to ensure each daughter cell gets 1 nucleus
        
        each gets a haploid nucleus
        
        initially karyokinesis
        
        preceding both - mandatory period of growth - interphase
  - - - purpose
        
        meiosis 1 - separation of homologous chromosomes forming 2 daughter where no. of chromosomes is reduced to half
        
        have double dna content
        
        meiosis 2
        
        end - 4 daughter chromosomes having half the no. of chromosomes and half the dna content
      - crossing over
        
        only in meiosis 1, not in meiosis 2
      - significance of meiosis
        
        maintaining chromosomal number
        
        haploid gamete comes together
        
        and zygote formed is the same no of chromosomes formed, since it was halved before
        
        genetic variation
        
        across generations
  - - - in animal - particular location - near the er
        
        in plant - present throughout the cell
        
        just before cell plate is formed
        
        golgi bodies accumulate enzymes, structural proteins and glucose
        
        begin to start breaking up into relatively membrane bound sac like structures called vesicles
        
        before this, they accumulate everything
        
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    - - becomes complete till telophase
        
        forming highly vesicles structure called phragmoplast
    - - called centrifugal cytokinesis
    - - its initiated early
        
        beginning of cytokinesis starts in interphase
        
        terminated only in telophase
  - - - no cell wall, so much shorter
    - - contractile ring composed of actin filaments is formed in equatorial regions just under cell membrane
    - - contractile - can contract
        
        begins to
        
        cell membrane is pulled from periphery forming a depression - cleavage furrow/fissure/ cell furrow
    - - contract even further - deepening of furrow forming a midbody
        
        just before cytokinesis is complete
        
        only a narrow stretch of cytoplasm connecting cells
    - - contracts fully
        
        pinches off 2 daughter cells
    - - fm outside to center
- - - - 22 matching pairs of chromosomes
        
        not only arranged on basis of size
        
        but paired and numbered
    - - in one corner of a karyogram
        
        normal chromosomes - aka autosomes
        
        basic and fundemental units
        
        autosomes are those kinds of chromosomes which always exist as pairs in the body cells
        
        and have genes that code for physical or physiological features
        
        not autosomes
        
        x and y (male) or x and x (female)
    - - same banding pattern
        
        when chromosomes are stained, they stain intensely in certain regions depending on no of genes together on locus
        
        all homologous have same banding pattern when stained
        
        they take up the stain because how conc the genes are
        
        since same types of genes in same places
        
        only allele is different
    - - a specific segment of the dna that codes for a specific polypeptide
        
        a specific part of a chromosome that controls the expression of a specific character
  - - - ones that come together and pair up during prophase 1 of meiosis 1 to form bivalent chromosomes
- - - - a haploid cell
        
        only one copy of each chromosomes
      - usually gametes are haploid
  - - - somatic cells are diploid
- - - - growth - zygote undergoes divisions forming a multicellular organism
        
        every time it divides, it forms daughter cells
        
        genetically identical - clones
        
        this division which contributes to growth
        
        called Mitosis
        
        in all somatic cells
        
        at end - 2 daughter cells
        
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      - sexual reproduction
        
        fertilisation
        
        fusion of the. nuclei of male and female gametes forming a zygote
        
        just before fertilisation, chromosomal number needs to be reduced to half
        
        male is a diploid organism, but produces haploid sperm
        
        like female
        
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