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Biology > 5.2 > Flashcards

5.2 Flashcards

1
Q

what is a model?

A

A model is a 3D representation of a particular structure. Models are often effective communicating the idea and behaviour of a particular structure. However, they are often oversimplified, lacking structural details, and are not to scale.

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2
Q

what happens if an incorrect replication occurs and how can it turn out.

A

well it will result likely in a mutation. this mutation will either be favourable or disadvantageous. Favourable being it causing variation whilst a con creating unfavourable traits, impairing dna replication and protein synthesis

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3
Q

what are chromosomes composed of?

A

they compose of histones, DNA, and genes

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4
Q

homologous chromosomes have….

A

have identical genes, but each chromosome of the homologous pair may code for a different ‘variant’ of the gene, termed allele. one variant is usually dominant whilst the other is recessive

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5
Q

what r three factors that identify mitosis

A

-occurs in all body tissues by somatic cells

-produces two genetically identical diploid daughter cells

-occurs for the purpose of growth, repair and maintanence

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6
Q

what are the stages of mitosis

A

ipmat

interphase

prophase

metaphase

anaphase

telophase - cytokenesis

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7
Q

what must be done before interphase for mitosis to occur

A

the somatic cell must be present which is a diploid cell and homologous. This is the parent cell thatll be utilised for the process

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8
Q

what occurs in interphase of mitosis

A

DNA undergoes replication.

There should be two identical copies of chromosomes (4n). In human cells, its going from 46 strands of DNA chromosomes to 92. Longest phase

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9
Q

What occurs in prophase of mitosis (3)

A

DNA condenses into chromosomes of an x shape and joins its sister chromatid at the centromere

  • Nuclear membrane disappears
  • The spindle fibres are preparing for metaphase to attach to the chromosomes
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10
Q

what occurs in metaphase in mitosis

A

the chromosomes align in the middle along the equator

  • Centrioles move to the poles
  • Spindle fibres which are created from the centrioles extend from it and attach at the centromeres of the chromosome
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11
Q

what occurs in anaphase of mitosis

A

Spindle fibres pull the chromatids towards the opposite side of poles.

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12
Q

what occurs in telophase of mitosis

A

the nuclear membrane reforms.This is where cytokinesis begins as cell cleavage is visible.

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13
Q

what is cytokenesis in mitosis

A

cytokinesis is the physical splitting of the daughter cell into two done by microfilaments. Microtubules contract and pinch the cells apart.

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14
Q

what is meiosis and whats the key difference from mitosis

A

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes

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15
Q

what is the role of meiosis?

A
  • During sexual reproduction, two parents are involved in passing genetic material on to offspring.
  • To prevent the chromosome number from doubling in each generation, meiosis occurs and produces gametes with half the full number of chromosomes.
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16
Q

what is the difference between diploid and haploid

A

diploid
containing two sets of chromosomes
* Chromosomes are in PAIRS, homologous chromosomes

  • 2 copies of each chromosome (one maternal, one paternal)

haploid
* Containing one set of chromosomes
* Cells have half the full number of chromosomes
* ONE of each pair
* Chromosomes are single

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17
Q

what are the steps in meiosis

A

PMATPMAT

18
Q

what differentiates miosis prophase 1 from mitosis

A

in prophase 1 of miosis, the chromosomes match up with their homologous pairs. one comes from mom and one comes from dad. They then cross over

19
Q

what differentiates metaphase 1 of meiosis from mitosis

A

the chromosomes align in the middle in their homolgous pairs aligning along the equator with the spindle fibres connected to centremeres. independent assortment occurs here

20
Q

what differentiates anaphase 1 of meiosis from mitosis

A

In anaphase the spindle fibres pull the chromosomes apart instead of the chromatids in mitosis

21
Q

what occurs in telophase 1 in meiosis

A

the same thing occurs like mitosis, 2 cells are created

22
Q

what occurs in cyotkenesis of miosis

A

same thing as mitosis, it physically splits into 2 daughter cells

23
Q

what occurs in meiosis 2 , prophase

A

same thing as mitosis prophase, Chromosomes are condensing in both daughter cells but there is no homologous pairs and crossing over

24
Q

what occurs in meiosis 2, metaphase

A

Nuclear membrane already broke down in previous stage and they algin against the equator (similar to mitosis

25
Q

what occurs in anaphase 2 in meiosis

A

Chromatids are pulled away
-random segragation occurs here

26
Q

what occurs in telophase and cyotkenesis

A

same thing except itll create 4 unique daughter cells instead of 2

27
Q

What are the main differences between meiosis and mitosis

A

somatic cells/germ cells
1 division/ 2 division
genetically identical/genetically different

in prophase 1, chromosomes do not pair up and do not cross over.

homologous chrmsomes pair up to form (bivalent)

28
Q

what is independent asortment?

A
  • occurs during Metaphase I of Meiosis
  • the process where the alleles specifying for different genes (in non-homologous chromosomes) assort themselves independently.
  • Independent Assortment in Metaphase I results in the separation of double-stranded CHROMOSOMES from their homologous pairs in Anaphase I.
29
Q

how does independent assortment increase genetic variation?

A

the double-stranded chromosomes in their non-homologous pairs can be aligned independently to the other non-homologous pair which will increase genetic variation for the two haploid cells formed in cytokinesis I. Therefore, independent assortment will determine the alleles for different genes such each of the two haploid cells can inherit which, ultimately, affects the allele for each gene that each gamete can inherit at the end of Cytokinesis II in Telophase II.

30
Q

what is random segration

A
  • Random Segregation of chromatids (chromosomes) occurs in Anaphase II of Meiosis II
  • Random Segregation deals with separating CHROMATIDS of EACH double-stranded chromosome.
31
Q

how does random segragation increase genetic variation?

A

Anaphase II in the Meiosis II

-crossing over increases genetic variation by segregating one chromatid that may or may not have undergone crossing over to different poles of each haploid cell which further divides into gametes during Cytokinesis II in Telophase II.

Therefore, the resulting gamete may inherit different alleles for different genes.

32
Q

describe the chracteristics of DNA replication

A
  • DNA replication is semiconservative (the two strands of nucleotides separate)
  • The two DNA strands are antiparallel (run in opposite directions)
  • DNA has complementary base pairing
  • Hydrogen bonds hold nucleotides together
  • Between adenine and thymine, there are 2 hydrogen bonds
  • Between guanine and cytosine, there are 3 hydrogen bonds
33
Q

what r the structures in DNA replication

A
  • Helicase
  • DNA
  • torsional strain
  • topoismerase
  • SSB proteins
  • RNA primer
  • Primase
  • dna polmerase 3
  • leading strand
  • lagging strand
  • okazaki fragments
  • dna polmerase 1
  • dna ligase
34
Q

describe the process of dna replication

A

refer to notes pg 30-31

35
Q

what is 5’ to 3’

A

The 5’ and 3’ indicates the directionality of a DNA strand. The 5’ carbon has a phosphate group attached to it and the 3’ carbon a hydroxyl group.

36
Q

what is the final result of dna replication

A

The end result is that there are 2 molecules of DNA, each a double stranded helix, identical to each other and the original molecule.

37
Q

what does the watson and crick model show

A
  • Watson and Crick’s model of DNA showed a large linear molecule arranged as a double helix or ‘twisted ladder’, with 4 nitrogenous bases held in pairs by hydrogen bonds

-showing super phosphate back bone, nitrogenous bases, hydrogen bonds and the overal nucleotides

38
Q

explain the importance of accuracy during DNA replication

A

Heredity – relies on DNA replication
* Genetic material of a cell must be transmitted from one cell to another during mitosis, allowing for growth, repair, and maintenance of an organism.

Gene expression – this relies on protein synthesis
* Genes are expressed in terms of the proteins they produce.
* If there is a mistake in DNA replication, this may have a direct effect on the phenotype of the individual. This is because a dysfunctional or no protein is made.
* Since many proteins are enzymes and control chemical reactions of a cell, errors in replication can affect the functioning of an individual.

39
Q

assess the effect of mitosis on the continuity of species

A

Mitosis basically produces clones, thus ensuring that favourable characteristics are inherited by offspring throughout the population if those clones do uphold favourable traits. This is seen in plants’ runners leading to new plants that are clones (genetically identical) of their parents.

40
Q

assess the effect of miosis on the continuity of species

A

Crossing over occurs during Prophase I of meiosis where non-sister chromatids in homologous pairs exchange genetic materials, creating new allele combinations. the increased genetic variation reduces the probability that a sudden change in environment will lead to an extinction event

41
Q

assess the effect of replication on the continuity of species

A

If DNA were not replicated before mitosis and meiosis, cell division would halve the amount of DNA, and resulting cells would die due to inadequate amounts of genetic information.

42
Q

illustrate the disadvantages when genetic material is replicated exactly

A

It will not be ideal for a parent with unfavourable characteristics to be passing on undesirable characteristics (allele combinations) to offsprings via mitosis. Therefore replicating DNA exactly will be bad in this situation. Even if all of the parents’ characteristics that are passed down to offsprings are favourable, exact replication of genetic would decrease genetic variation in a population. So, in the event of a sudden change for a species’ ambient environment, there may be a threat of extinction.

Biology (9 decks)

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