5.2

Question 1

what is a model?

Answer 1

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.

Question 2

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

Answer 2

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

Question 3

what are chromosomes composed of?

Answer 3

they compose of histones, DNA, and genes

Question 4

homologous chromosomes have….

Answer 4

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

Question 5

what r three factors that identify mitosis

Answer 5

-occurs in all body tissues by somatic cells

-produces two genetically identical diploid daughter cells

-occurs for the purpose of growth, repair and maintanence

Question 6

what are the stages of mitosis

Answer 6

ipmat

interphase

prophase

metaphase

anaphase

telophase - cytokenesis

Question 7

what must be done before interphase for mitosis to occur

Answer 7

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

Question 8

what occurs in interphase of mitosis

Answer 8

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

Question 9

What occurs in prophase of mitosis (3)

Answer 9

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

Question 10

what occurs in metaphase in mitosis

Answer 10

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

Question 11

what occurs in anaphase of mitosis

Answer 11

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

Question 12

what occurs in telophase of mitosis

Answer 12

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

Question 13

what is cytokenesis in mitosis

Answer 13

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

Question 14

what is meiosis and whats the key difference from mitosis

Answer 14

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

Question 15

what is the role of meiosis?

Answer 15

• 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.

Question 16

what is the difference between diploid and haploid

Answer 16

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

Question 17

what are the steps in meiosis

Answer 17

PMATPMAT

Question 18

what differentiates miosis prophase 1 from mitosis

Answer 18

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

Question 19

what differentiates metaphase 1 of meiosis from mitosis

Answer 19

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

Question 20

what differentiates anaphase 1 of meiosis from mitosis

Answer 20

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

Question 21

what occurs in telophase 1 in meiosis

Answer 21

the same thing occurs like mitosis, 2 cells are created

Question 22

what occurs in cyotkenesis of miosis

Answer 22

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

Question 23

what occurs in meiosis 2 , prophase

Answer 23

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

Question 24

what occurs in meiosis 2, metaphase

Answer 24

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

Question 25

what occurs in anaphase 2 in meiosis

Answer 25

Chromatids are pulled away -random segragation occurs here

Question 26

what occurs in telophase and cyotkenesis

Answer 26

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

Question 27

What are the main differences between meiosis and mitosis

Answer 27

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)

Question 28

what is independent asortment?

Answer 28

* 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.

Question 29

how does independent assortment increase genetic variation?

Answer 29

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.

Question 30

what is random segration

Answer 30

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

Question 31

how does random segragation increase genetic variation?

Answer 31

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.

Question 32

describe the chracteristics of DNA replication

Answer 32

* 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

Question 33

what r the structures in DNA replication

Answer 33

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

Question 34

describe the process of dna replication

Answer 34

refer to notes pg 30-31

Question 35

what is 5' to 3'

Answer 35

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.

Question 36

what is the final result of dna replication

Answer 36

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

Question 37

what does the watson and crick model show

Answer 37

* 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

Question 38

explain the importance of accuracy during DNA replication

Answer 38

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.

Question 39

assess the effect of mitosis on the continuity of species

Answer 39

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.

Question 40

assess the effect of miosis on the continuity of species

Answer 40

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

Question 41

assess the effect of replication on the continuity of species

Answer 41

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.

Question 42

illustrate the disadvantages when genetic material is replicated exactly

Answer 42

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.