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molecular and cellular biology > mitosis and meiosis > Flashcards

mitosis and meiosis Flashcards

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1
Q

chromosomes in prokaryotic cells

A
  • in pro there is often only one chromosome containing all the genes.
  • the DNA is not complexed with protein
  • chromosomes are not visible in light microscopes
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2
Q

chromosomes in eukaryotic cells

A
  • in eukaryotic cells there are often several linear chromosomes
  • the DNA is complexed with protein –histones (right)
  • with the right staining and at certain times in the cell cycle (when the cells are dividing) these chromosomes can be visible in the light microscopes
  • having multiple chromosome results in eukaryotes having more complex genetics and inheritance than prokaryotes
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3
Q

where is the sets of info present in euk cells

A

in the nucleus

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4
Q

what are cells with one set of genetic info called and give an example

A

haploid cells e.g. human sperm and egg cells

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5
Q

what are cells with two set of genetic info called and give an example

A

diploid e.g. human somatic cells(somatic cells are non-inherited cells of our body)

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6
Q

non sexual cell division

A

mitosis

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7
Q

sexual cell division

A

meiosis

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8
Q

do pro undergo sex

A

pro do not undergo sex in the true sense

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9
Q

do euk undergo sex

A

euk undergo sexual and asexual reproduction

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10
Q

what is mitosis

A

it is cell division of the one euk cell which produces 2 identical daughter cells

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11
Q

what does mitosis do in unicellular organisms

A

it increases the number of cells in a population

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12
Q

what does mitosis do in multicellular organisms

A

it is often followed by differentiation of the cells to produce specialised cells

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13
Q

what is meiosis

A

it is cell division of one euk tetraploid cell which produces two diploid cells of different genotypes. this is then followed by division to form 4 haploid cells. the cells produced are non identical.

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14
Q

what do the cells in meiosis differentiate into

A

gametes (sex cells)

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15
Q

similarities of mitosis and meiosis

A

s phase- the DNA in the cell is replicated once.

each chromosome now consists of two lengths of DNA called chromatids

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16
Q

differences between mitosis and meiosis

A

in meiosis in the first division is immediately followed by a second division with no DNA replication

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17
Q

in both forms of cell division the order of stages is?

A

interphase – long stage with uncondensed chromosomes
Prophase – chromosomes condense & the nuclear envelope breaks down
Metaphase – the chromosomes line up at the chromosome equator
Anaphase – the chromosomes are separated by microtubules
Telophase– the chromosomes reach the opposites poles of the cells followed by cytokinesis

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18
Q

what is recombination

A

recombination is a process in which homologous chromosomes exchange DNA strands

19
Q

what does recombination result in

A

the process results in the inheritance of new combinations of maternal and paternal alleles

20
Q

how many recombination genes including female and male

A
  • Recombination rates vary across the genome by approximately 1000 fold
  • Female germ cells have approximately 80 recombination events per meiosis
  • Male germ cells have approximately 50 recombination events per meiosis
21
Q

How are genes presented in euk

A

gene is present on linear chromosome

22
Q

when does recombination take place

A

shuffling of genes between homologous chromosomes – takes place during meiosis

23
Q

mitosis stages

A 
G1 
S 
G2
all the above is interphase 
M
Interphase 
prophase 
metaphase
anaphase 
telophase 
cytokinesis
now explain what happens in these stages
24
Q

meiosis stages

A 
interphase 
prophase 1
metaphase 1
anaphase 1 
telophase 1
cytokinesis
meiosis second division 11-
both daughter cells undergo prophase 11 metaphase 11 anaphase 11 telophase 11 cytokinesis
25
Q

G1 cell cycle

A
  • cell grows and new organelles and proteins made

- checks for any damage of DNA and if the chemicals needed for replication are present before entering S phase

26
Q

Synthesis (s phase) cell cycle

A

cell replicates its DNA ready to divide by mitosis

27
Q

G2 cell cycle

A

cell keeps growing and proteins needed for cell division are made
-cell checks if all DNA is replicated without damage.
if not damaged then enter mitosis

28
Q

what is mitosis

A

it is needed for growth of multicellular organisms and for repairing damaged tissues.
also a method of asexual reproduction for some plants animals and fungi.

29
Q

interphase (mitosis)

A
  • DNA is unravelled and replicated to double genetic content
  • organelles also replicate
  • ATP content is increased
30
Q

prophase (mitosis)

A
  • chromosomes condense get shorter and fatter
  • tiny bundles of proteins called centrioles start moving to opposite ends of cell forming a network of protein fibres across it called the spindle
  • nuclear envelope breaks down and chromosome lie free in the cytoplasm
31
Q

metaphase (mitosis)

A
  • chromosomes line up along the middle of the cell and become attached to the spindle by their centromere
  • the cell checks that all chromosomes are attached to the spindle before mitosis continues
32
Q

anaphase (mitosis)

A
  • centromeres divide separating each pair of sister chromatids
  • spindles contract pulling chromatids to opposite ends of the cell
33
Q

telophase (mitosis)

A
  • chromatids reach opposite poles on the spindle
  • they uncoil and become long and thin again
  • they’ve now called chromosomes again
  • a nuclear envelope forms around each group of chromosomes so there are now two nuclei
34
Q

cytokinesis (mitosis)

A
  • cytoplasm divides
  • two daughter cells that are genetically identical to the original cell and to each other
  • cytokinesis usually begins at anaphase and ends up t telophase.
35
Q

what is meiosis

A

meiosis produces gametes for sexual reproduction

meiosis involves two divisions meiosis 1 and meiosis 11

36
Q

interphase (meiosis)

A

DNA unravels and replicates to produce two chromosomes called sister chromatids

37
Q

prophase 1 (meiosis 1)

A

chromosomes condense getting shorter and fatter
chromosomes arrange themselves into homologous pairs and crossing over occurs
centrioles start moving to opposite ends of the cell forming spindle fibres
nuclear envelope breaks down
during prophase 1 the homologous pairs of chromosomes come together and pair up. the chromatids twist around each other and bits of chromatids swap over.
the chromatids still contain same genes but now have different combinations of alleles

38
Q

metaphase 1 (meiosis 1)

A

homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres

39
Q

anaphase 1 (meiosis 1)

A

spindles contract separating the homologous pairs- one chromosome goes to each end of the cell

40
Q

telophase 1 (meiosis 1)

A

nuclear envelope forms around each group of chromosomes

41
Q

cytokinesis (meiosis 1)

A

division of the cytoplasm occurs and two haploid daughter cells are produced

42
Q

meiosis 11

A

the two daughter cells undergo prophase 11, metaphase 11, anaphase 11, telophase 11 and cytokinesis
(those stages are like mitosis)

43
Q

anaphase 11 (meiosis 11)

A

the pairs of sister chromatids are separated- each new daughter cell inherits one chromatid from each chromosome. four haploid daughter cells are produced- these are the gametes

44
Q

two main events that lead to genetic variation in meiosis

A

1) crossing over of chromatids
- crossing over of chromatids in meiosis 1 means each 4 daughter cells formed contains chromatids with different alleles. occurs in prophase 1
2) independent assortment of chromosomes
- each homologous pair of chromosomes in your cells is made up of one chromosome from mum and one chromosome from dad
- when homologous pairs line up in metaphase 1 and separated in anaphase 1, its completely random which pair ends up in which daughter cell
- so 4 daughter cells have completely different combinations of maternal and paternal chromosomes
- this is called independent assortment of chromosomes
- this shuffling of chromosomes lead to genetic variation in any potential offspring

molecular and cellular biology (5 decks)

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