Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

biolala > Cell division > Flashcards

Cell division Flashcards

differences between mitosis and meiosis on page 13 and very useful graph on page 14 - IMPORTANT

1
Q

what does the DNA exist as if it is not dividing?

A

chromatin within the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

describe chromatin

A

consists of DNA and histone proteins and is found in the nucleus of eukaryotic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what happens to chromatin when cell division begins?

A

chromatin condenses to form chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do chromosomes consist of and what is DNA made up of?

A

consist of DNA, protein and little RNA

made up of many small sections called genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are chromosomes found as in diploid cells?

A

they are found in matching pairs called homologous chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe what happens at the start of cell division (already mentioned that chromatin condenses to chromosomes)

(chromatids and centromere labelled diagram on page 2)

A

DNA replicates during interphase and the chromosomes are visible as two identical sister chromatids joined at the centromere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how many pairs of homologous chromosomes do humans have and give examples of other species?

A

human have 23 pairs

cats - 19 pairs
fruit flies - 4 pairs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe where each homologous pair comes from?

A

consists of one chromosome inherited from the mother and one inherited from the father

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the meanings of diploid and haploid

A

diploid - the total number of chromosomes in a somatic (body) cell as there are two of each type of chromosome (2n)

haploid - gametes (sex) cells have one of each type of chromosome (i.e. half the diploid number) so are haploid (n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe the first part of the cell cycle: interphase (what happens)

A

majority of cell cycle spent in interphase

a newly formed cell increases in size and performs several activities:
DNA replicates
organelles are produced
protein synthesis occurs
ATP synthesis occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

mitosis is the division of the nucleus that occurs in 4 phases and what are these phases?

A

prophase

metaphase

anaphase

telophase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe prophase and draw it out

A

chromatin condenses into visible sister chromatids joined at the centromere

centrioles move to opposite poles, forming protein microtubules and developing the spindle

the nuclear envelope disintegrates, the nucleolus disappears, and the chromosomes move towards the cell equator

prophase is the longest stage of mitosis

(diagram on page 4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe metaphase and draw it out

A

chromosomes align along the cell equator and attach to spindle fibres at the centromere

(diagram on page 4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe anaphase and draw it out

A

a rapid stage in which spindle fibres contract and shorten, the centromere splits, and sister chromatids are pulled apart

chromatids are drawn towards the opposite poles with the centromere leading

(diagram on page 5)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe telophase

A

chromosomes uncoil and lengthen

spindle fibres break down

nucleolus and nuclear envelope reform (two of them)

(diagram on page 5)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe cytokinesis (splitting of the cytoplasm)

A

in animal cells, cytokinesis occurs by constriction of the parent cell from the outside inwards, forming a cleavage furrow

in plant cells, a cell plate forms across the equator of the parent cell from the inside outwards, and a new cellulose cell wall is laid down

(cytoplasm divides and there are two genetically identical daughter cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

during mitosis what is the shape of the animal cells compared to the plant cells?

A

animal - cells become rounded before mitosis

plant - no shape change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

during mitosis are the centrioles present in animal cells compared to the plant cells?

A

animal - present

plant - absent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

describe the difference between animal cells and plant cells during cytokinesis (repeated info)

A

animal - cleavage furrow develops from the outside inwards, pinching the cytoplasm

plant - cell plate develops from the centre outwards, forming a new cell wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what happens to the spindle fibres in animal cells compared to plant cells?

A

animal - degenerates at telophase

plant - remains throughout new cell wall formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

where does mitosis occur in animal cells compared to plant cells?

A

animal - in epithelial tissue, bone marrow and other sites
in human skin, mitosis replaces dead surface cells with genetically identical cells from below

plant - in meristems (tips of root and shoots)

22
Q

what does mitosis produce?

A

two daughter cells with the same number of chromosomes as the parent cell

each chromosome is an exact replica of one of the original chromosomes so mitosis produces cells that are genetically identical to the parent cell, ensuring genetic stability

23
Q

what does mitosis lead to?

A

growth of an organism, repair of damaged tissues. and replacement of dead cells

24
Q

define and describe asexual reproduction and give examples

A

produces offspring through mitosis, so that the offspring are genetically identical to the parent

there is no genetic variation so they are clones

strawberry runners, daffodil bulbs, potato tubers

25
what do most animals and plants produce which enable sexual reproduction?
produce haploid gametes which are not identical to the parent cell
26
what are the advantages of asexual reproduction?
offspring are genetically identical to the parent, so they are able to survive successfully if environmental conditions are stable less time and energy are required as there is no need to produce gametes and find a reproductive partner
27
what is a disadvantage of asexual reproduction?
lack of genetic variation means offspring cannot adapt to changing environmental conditions
28
why is the length of the cell cycle controlled by genes?
ensures mitosis occurs where and when it is needed such as for tissue repair and replacement of tissues in adults and correct development in embryos
29
what are carcinogens?
can mutate DNA and affect the genes that control the cell cycle e.g. radiation, certain chemicals and some viruses
30
what are proto-oncogenes and how can they become oncogenes?
they regulate the cell cycle by signalling when cells should divide if these genes mutate, uncontrollable cell division can occur, leading to tumour formation these mutated genes are called oncogenes
31
what are two types of tumour that can form?
benign - non-cancerous and won't invade nearby tissues malignant - cancerous and can spread to other tissues
32
what is mitotic index?
it is proportional to the time each cell spends carrying out mitosis this can be modified to show the time each cell spends undergoing that stage
33
how to calculate mitotic index?
count the total number of cells in the field of view count the number of cells that are dividing (in prophase, metaphase, anaphase or telophase) mitotic index = number of actively dividing cells in field of view / total no. of cells in field of view
34
what does meiosis produce?
gametes in sexually reproducing organisms, resulting in four genetically different daughter cells
35
how many stages of cell division does mitosis involve?
two
36
what are the two stages of meiosis?
meiosis I - chromosome number is halved meiosis II - haploid cells divide again, producing four genetically different daughter cells (similar to mitosis)
37
describe prophase I and draw it out
chromosomes condense into visible sister chromatids joined at the centromere homologous chromosomes pair up in a bivalent chromatids from homologous pairs wrap around each other and then partially repel each other but remain joined at points called chiasmata - where homologous chromosomes can exchange equivalent sections of DNA this swapping is called crossing over nuclear envelope disintegrates, nucleolus disappears, centrioles move to opposite poles and spindle microtubules form (diagram on page 9)
38
describe metaphase I and draw it out
chromosomes align themselves either side of the equator in their homologous pairs, attached to spindle fibres at their centromeres homologous pairs of chromosomes (bivalents) align randomly along the equator, leading to independent assortment this results in a random combination of paternal and maternal chromosomes in each daughter cell (diagram on page 9)
39
describe anaphase I and draw it out
spindle fibres contract and shorten, separating bivalents and chromosomes are pulled to opposite poles each pole receives one chromosome from each homologous pair this results in a random mix of maternal and paternal chromosomes due to independent assortment in metaphase I (diagram on page 10)
40
describe telophase I and draw it out and cytokinesis
in some species, the nuclear envelope reforms around the haploid chromosomes, which uncoil and lengthen in many species, chromosomes remain condensed cytokinesis - when the cytoplasm is divided, producing two haploid cells (diagram on page 10)
41
what happens at prophase II and metaphase II and draw them out
prophase II - centrioles migrate to the poles and new spindle develops at right angles to the previous one metaphase II - chromosomes align on the equator attached to spindle fibres at their centromere independent assortment occurs with chromatids randomly facing either pole (diagram on page 11)
42
what happens at anaphase II and draw it out
spindle fibres contract and shorten centromeres split, and sister chromatids are pulled to opposite poles (diagram on page 11)
43
what happens to telophase II and cytokinesis and draw it out
telophase II - chromosomes uncoil and lengthen and are no longer visible under the microscope spindle breaks down nuclear envelope and nucleolus reform (diagram on page 11) cytokinesis produces four haploid daughter cells
44
what is essential for a species to survive in a constantly changing environment?
to have sources of genetic variation
45
what three ways does meiosis introduce genetic variation?
crossing over independent assortment random fusion of haploid gametes
46
describe crossing over (good diagram on page 12)
during prophase I, chromosomes condense and homologous pairs form a bivalent, this process is called a synapsis chromatids in the bivalent join at the chiasmata, where parts of the chromosome may be exchanged this process is called crossing over
47
describe independent assortment
during metaphase I and II, chromosomes randomly distribute themselves at the equator of the cell this random distribution leads to independent assortment of chromosomes with 3 pairs of chromosomes, there are 2^3 = 8 possible combinations of maternal and paternal chromosomes
48
describe random fusion of haploid gametes
at fertilisation, the diploid chromosomes number is restored, when two random haploid gametes fuse to form a zygote half of the chromosomes in the new cell come from the maternal gamete, and half come from the paternal gamete
49
what are the advantages of sexual reprouction?
allows offspring to adapt to a changing environment, this allows natural selection to take place spores produced by fungi and seeds by plants are dispersed widely to help reduce intraspecific competition
50
suggest an organ present in a mammal which contains cells capable of dividing by both mitosis and meiosis?
testicles / ovaries

biolala (32 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions