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    What happens to DNA mass in meiosis?

    quarters

    Okay, so the mass of DNA in meiosis quarters.
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    What happens to Chromosome number in meiosis?

    halves

    The chromosome number in MEIOSIS halves.
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    As a comparison:

    Mitosis

    (Original post by anon_98)
    what happens to dna mass in mitosis?

    halves

    okay so the mass of the dna halves in mitosis.

    In mitosis, the mass of dna halves.
    (Original post by anon_98)
    what happens to chromosome number in mitosis?

    stays the same

    the chromosome number in mitosis stays the same.

    Basically nothing happens.
    vs


    Meiosis

    (Original post by anon_98)
    what happens to dna mass in meiosis?

    quarters

    okay, so the mass of dna in meiosis quarters.
    (Original post by anon_98)
    what happens to chromosome number in meiosis?

    halves

    the chromosome number in meiosis halves.
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    Anon you are fantastic :hugs: reading this is also helpful since the new AS course is similar,
    don't reply to this because i dont want to waste your time but you are fab and good luck :lovehug:
    night night x
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    Describe Semi-Conservative Replication? produces 2 identical copies of the DNA – each has half the old strand and half the new strand. Process:

    −DNA Helicase breaks hydrogen bonds between the complementary bases

    −Double strand separates, leaves 2 template stands

    −Free complementary nucleotides bind (A to T, C to G)

    −DNA Polymerase joins the sugar-phosphate backbone of the new strand

    Alright, so there are 4 steps to semi conservative replication.

    Semi conservative replication produces 2 identical copies of the DNA. Each has half the old strand and half the new strand. So, it produces 2 identical copies of the DNA. Half new. Half old. That's half new, half old. Okay.

    It goes:

    DNA Helicase breaks the Hydrogen bond.

    Helicase breaks the Hydrogen. - Between the complementary base pairs.

    THEN. the double strand separates leaving you with 2 template strands.

    THEN the free complementary nucleotides bind.

    THEN we have DNA polymerase which joins the sugar-phosphate backbone of the new strand. Hm.

    So overall, the DNA helicase breaks the hydrogen bonds between the base pairs then the double strand separates bc we know by now that hydrogen bonds are pretty weak then it leaves you with two templates strands. The nucleotides which are free begin to bind then the DNA polymerase joins the sugar-phosphate backbone of the new strand.
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    (Original post by Salamandastron)
    Anon you are fantastic :hugs: reading this is also helpful since the new AS course is similar,
    don't reply to this because i dont want to waste your time but you are fab and good luck :lovehug:
    night night x
    :cube: :heart:

    Goodnight Cavy, + Good luck for tomorrow.
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    Evidence for Semi conservative replication?

    DNA made of 15N (heavy nitrogen) is replicated in an environment of 14N (light nitrogen) – produces DNA molecules with half 15, half 14 – medium density

    Ah right, so Heavy Nitrogen which is 15N is replicated in an environment of the Light Nitrogen 14N.

    The light Nitrogen has the lower number.

    And it produces DNA molecules with Half 15, Half 14 which is of medium density.

    That's basically what we said before but in an example- half new, half old.
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    What is cancer?

    uncontrolled cell division (uncontrolled mitosis) leading to formation of a tumour.
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    Define a tissue, organ and organ system?

    Tissue - a group of specialised cells

    Organ - made of different tissues,

    Organ system - different organs working together

    Okay so a tissue is a group of specialised cells, an organ is made up of different tissues and an organ system is different organs working together.
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    What is genetic diversity?

    The variety of alleles within a population of a species.

    Okay so genetic diversity is the variety of alleles within a population of a species.

    Genetic diversity is a variety of alleles.

    variety lol.


    Benefit of high genetic diversity?

    species able to adapt with changes in the environment

    The benefits of a high genetic diversity is that the species is able to adapt with changes in the environment.

    So high GD = Adaptable = Good.


    What is selective breeding?

    interbreeding males and females with desired characteristics to produce offspring with the desired characteristics (inherit alleles) – lowers genetic diversity as all other alleles are excluded

    Selective breeding lowers the genetic diversity.

    Selective breeding lowersss the variety of alleles within a population of a species.

    What is the founder effect?

    small group from the main population becomes isolated, small number of individuals = low variety of alleles = low genetic diversity, if this group interbreeds and repopulates – all the individuals will have alleles from this limited range. if a mutated allele is present, individuals would be more likely to inherit the allele.

    What is a genetic bottleneck?

    large reduction in population size due to a natural disaster (or hunting), low number of individuals = low variety of alleles = low genetic diversity

    Okay, so both genetic bottlenecks and the founder effect REDUCE the genetic diversity.

    They both reduce the variety of alleles within a population of a species.
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    Okay genetic diversity stuff is now donee.

    Posted from TSR Mobile
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    Role of haemoglobin in oxygen transport?

    Haemoglobin loads oxygen in the lungs – due to high partial pressure of oxygen and low partial pressure of carbon dioxide, haemoglobin has a high affinity and becomes saturated (full).

    The haemoglobin is transported in the blood in the red blood cell.

    At the respiring tissues, oxygen is unloaded – due to low partial pressure of oxygen and high partial pressure of carbon dioxide, haemoglobin has low affinity and becomes unsaturated.

    Alright, so haemoglobin loads oxygen in the lungs bc of the high partial pressure of oxygen and low partial pressure of carbon dioxide. Haemoglobin has high affinity and becomes saturated.

    SO haemoglobin loads the O2 in the lungs, bc there's a high pp of O2 and a low pp of CO2. Haemoglobin has high affinity and becomes saturated. SATURATED.

    Then we have the respiring tissues, like muscle.

    And the oxygen is unloaded bc of basically the opposite:

    So, haemoglobin unloads oxygen due to the low partial pressure of O2 and high partial pressure of CO2. The haemoglobin has low afffinity and becomes unsaturated,


    Alright, so one more time:

    The o2 is loaded when there's a high pp of o2 and low co2 which means high affinity of haemoglobin which means saturated.

    Then o2 is unloaded when there;s a low pp of o2 and high co2, the heamoglobin has low affinity so it;s unsaturated.
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    Alright, so here's what the oxygen dissociation curves look like:

    The Y axis is supposed to say % saturation of Haemoglobin but I couldn't fit in. >.<



    Posted from TSR Mobile
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    Posted from TSR Mobile
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    And those are the three we need to know.

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    What is affinity?

    How well haemoglobin carries oxygen, its level of attraction.

    Affinity is how well haemoglobin carries O2.

    How well O2 is carried by haemoglobin.

    So if something has a high affinity, then I guess you could say it is carried incredibly well and has a high attraction for the something else.

    lol. :'3
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    Brb, I need a break. Just going to walk around my house.

    10 MINUTES.
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    Ohmyg, it ended up being almost 25 minutes. O_O

    I was clearly having too much fun. )':

    No, well I actually just needed to do lots of stuff + the time kinda escalated but it's done now so I can return to my work.
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    Alright ummmm..

    Affects of high levels of carbon dioxide on affinity?

    High partial pressure of carbon dioxide lowers affinity – occurs at the site of respiring tissues.

    The carbon dioxide lowers the pH of the blood, makes the haemoglobin change shape, so oxygen is released.

    This shifts the ODC to the right, called the bohr shift. Benefit = more oxygen delivered to respiring cell.

    So, Carbon dioxide lowers PH of blood and the haemglobin changes shape and O2 is released which shifts the curve to the right.
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    Benefit of fetal haemoglobin having high affinity?

    Fetal haemoglobin's ODC will be to the left, it has high affinity. In the placenta, there is low partial pressure of oxygen – so the oxygen will dissociate from the mother's haemoglobin, however the fetal haemoglobin will readily associate with the oxygen at the low partial pressures, so it has enough oxygen for its demands.

    Affinity of organisms in a low oxygen environment?

    Has a high affinity, curve to the left, therefore it can readily associate oxygen at the low partial pressures.

    So a low O2 environment means that the curve is to the left bc it has a high affinity.

    Affinity of active organisms?

    Has a low affinity, curve to the right, therefore more oxygen can be unloaded to meet it cells demand for respiration.

    Active = Curve to the right = More o2 unloaded.

    More O2 unloaded means that the demands for O2 for respiration are met.

    Affinity of small organisms?

    Have a large surface area to volume ratio, lose a lot of heat, needs to respire to generate heat, therefore has a low affinity, curve to the right, so unloads enough oxygen for the cells demand of respiration

    Small organisms have a large SA to volume ratio therefore they lose a lot of heat.

    A lot of heat is lost in small organisms and if you lose a lot of heat that means you need to respire to generate heat.

    And if you need to respire to generate heat then that means there is a low affinity, so the curve is to the right so unloads enough oxygen for the cells demand of respiration.
 
 
 
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