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biology > cell cycle and division > Flashcards

cell cycle and division Flashcards

1
Q

what are the stages of the cell cycle

A

Interphase
Mitosis
Cytokinesis

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2
Q

What happenes in Interphase

A

G1 phase - cell increases in size

S phase - DNA replicates by semi Conservative replication and starts to produce new organelles

G2 phase - cell prepares for division, Synthesis and stores of ATP

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3
Q

What is nuclear division

A

period when nucleus divides into 2 (mitosis) or 4 (meiosis)

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4
Q

What is cytokinises (cell division )

A

division of cytoplasm which follows nuclear division and process by which cytoplasm divides to form 2 or 4 new cells

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5
Q

what type of cells cannot undergo cell division

A

specialised cells, they must be made from stem cells

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6
Q

in what form is genetic information carried

A

in form of genes

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7
Q

what is a gene

A

section of DNA that codes for 1 specific polypeptide

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8
Q

what are intergenic regions

A

regions in DNA sequence between the genes

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9
Q

what is a chromosome

A

it’s an independent DNA molecule which has been supercoiled into a condensed form , which carries a specific set of genes

( chromosomes contains many different genes )

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10
Q

what does DNA supercoil using?

A

histone proteins

IN EUKARYOTIC CELLS ONLY

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11
Q

what are 2 condenses DNA molecule called when theyre still joined

A

identical sister chromatids

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12
Q

what is chromatin

A

DNA before supercoiling

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13
Q

what are somatic cells

A

body cells and they have their chromosomes in homologous pairs

they are also diploid

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14
Q

what are homologous chromosomes

A

have same genes in same gene loci but may have different alleles , one chromosome is maternal other is paternal

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15
Q

what does mitosis produce

A

2 diploid genetically identical daughter cells

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16
Q

what happens in prophase

A

1) The nuclear membrane starts to break down.

2) The centrioles start to move to the poles of the cell and make spindle fibres.

3) The chromosomes supercoil and condense / shorten / thicken and become visible.

4) Each chromosome appears as 2 identical sister chromatids joined at the centromere

17
Q

what happens in metaphase

A

1)The centrioles complete the production of spindle fibres (contractile protein fibres)

2)The chromosomes are attached to the spindle fibres by their centromere

3) the chromosomes align down the equator of the cell

18
Q

what happens in anaphase

A

1) The spindle fibres contract/shorten.

2)The centromere splits

3)The identical sister chromatids are pulled to opposite poles

4) making a “V” shape

19
Q

what happens in telophase

A

1)A nuclear membrane starts to reform around each set of chromosomes

2)The chromatids / chromosomes unwind / uncoil / become longer / thinner and become invisible.

20
Q

Describe the appearance and behaviour of chromosomes during mitosis: [5 marks]

A
  1. During prophase, chromosomes supercoil and condense to become visible;
  2. Chromosomes appear as 2 identical sister chromatids joined by a centromere;
  3. During metaphase chromosomes line up on the equator of the cell;
  4. Chromosomes attach to the spindle fibres;
  5. By their centromeres;
  6. During anaphase, the centromere splits;
  7. Sister chromatids are pulled to opposite poles of the cell making a V shape;
  8. During telophase, chromatids uncoil and become thinner;
21
Q

what do tumour suppressor genes code for

A

Tumour suppressor genes code for proteins that slow down the cell cycle.

22
Q

what do proto-onco genes code for

A

Proto-onco genes code for proteins that speed up the cell cycle

23
Q

what is a tumour

A

mass of abnormal cells

24
Q

give one method for treating cancer

A

give drugs that inhibit cell division
these drugs may stop dna replication, spindle formation , cytokinises

25
Q

give an example of asexual reproduction

A

binary fission in bacteria

26
Q

describe binary fission

A

replication of the circular DNA (not associated with histones) and of plasmids

The cell elongates from the middle, separating the two DNA molecules. A new cell wall (murein), is formed down the middle of the elongated cell which eventually meets, dividing the cell in two.

division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.

27
Q

describe virus replication

A

1) Attachment proteins on the virus attach to the receptors on the cell.

2) The virus nucleic acid enters the cells cytoplasm.

3) Reverse transcriptase makes DNA from viral RNA.

4) The viruses DNA is inserted into the host cells own nuclear DNA / genome.

5) The viral DNA is transcribed (viral mRNA) and translated into viral proteins (capsids/enzymes/attachment proteins).

6) The cell replicates the viral DNA.

7) The genetic material and proteins coats are assembled into virions.

8) Eventually these virions burst out of the cell, often destroying the host cell.

28
Q

where do viruses replicate and why

A

inside host cells, they use the host cells enzymes to replicate and transcribe viral DNA into viral mRNA translating into viral proteins

bc they dont have own ribosomes nd dna

29
Q

where does cell division in plants take place

A

root tips and shoot tips

30
Q

before you view a plant sample you must add which 2 solutions

A

50 degrees HCL - to break down cellulose cell wall ensuring stain can enter

ethano-orcein stain - to stain chromosomes and add contrast so they can be viewed under microscope

31
Q

formula for mitotic index

A

number of cells in PMAT / total num of visible cells

32
Q

why should you avoid moving the coverslip

A

it may damage / roll the chromosomes

33
Q

what organisms do meiosis

A

organisms that reproduce sexually

34
Q

what does meiosis produce

A

4 genetically different haploid daughter cells (gametes)

35
Q

why is meiosis important

A

halves the chromosome number (ensuring each egg or sperm only has one copy of each chromosome n) before fertilisation to restore the full chromosome number at fertilisation 2n.

36
Q

what are the stages of meiosis

A

P1 & M1: Chromosomes supercoil, condense (around histones) and become visible. Homologous pairs of chromosomes pair up (form a bivalent) and align along the equator. Spindle fibres attach to the centromere. Crossing over and independent segregation occurs here.

A1 : Spindle fibres contract and separate homologous chromosome pairs, pulling one of each pair to opposite poles of the cell.

T1 : Nuclear membrane reforms around the separated homologous chromosomes.

Each daughter cell is now HAPLOID (n).

P2 : Each daughter cell only contains one chromosome from each homologous pair (haploid).

M2 : Each chromosome aligns along the equator.

A2 : Non-Sister chromatids are split by their centromere and pulled to opposite poles of the cell.

T2 : Nuclear membrane reforms.

Four genetically different different haploid daughter cells are produced.

37
Q

what is crossing over

A
  1. The homologous chromosomes associate / Bivalent is formed.
  2. Chiasma(ta) form (Chromosomes entangle / twist).
  3. Equal lengths of (non-sister) chromatids / alleles are exchanged.
  4. Producing new combinations of alleles.
38
Q

when does crossing over happen

A

during metaphase 1

39
Q

what is independent segregation

A

During Metaphase 1, maternal and paternal chromosomes are reshuffled in any combination on the equator of the cell

biology (17 decks)

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