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Biology OCR A Alevel > Cell Devision > Flashcards

Cell Devision Flashcards

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1
Q

What stages are within interphase?

A

G1, S, G2

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2
Q

What takes place in G1?

A

Protein synthesis of proteins that synthesise organelles

Organelle replication

Cell growth

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3
Q

What takes place in the S phase?

A

Dna replication

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4
Q

What takes place in g2?

A

Energy stores increased

Duplicated dna checked for errors

Cell growth

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5
Q

What are the 3 checkpoints of the cell cycle?

A

G1 check point

G2 checkpoint

Spindle assembly checkpoint

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6
Q

What is checked for in the g1 checkpoint?

A

Cell size

Nutrients

Growth factors

Dna damage

once satisfied DNA replication is triggered

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7
Q

What is checked for in the G2 checkpoint?

A

Cell size

Dna replication

Dna damage

once satisfied the cell initiates molecular processes that signal the start of mitosis

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8
Q

What is checked for and when does the spindle assembly checkpoint occur?

A

Check chromosomes are attached to spindles

Occurs in metaphase before it can proceed to anaphase

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9
Q

What happens in prophase of mitosis?

A

Chromatin fibres cool and condense to form chromosomes
Nucleolus disappears and nuclear envelope breaks down
Centrioles migrate to poles which aids Spindles assemble

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10
Q

What happens in metaphase or mitosis?

A

Chromosomes are moved to the metaphase plate by spindle fibres

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11
Q

What happens in anaphase of mitosis?

A

Centromeres divide

Chromatids separate and are moved to opposite poles by contracting spindle fibres

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12
Q

What happens in telophase of mitosis?

A

Nuclear membrane reforms and chromosomes uncoil to chromatin and cytokinesis begins`

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13
Q

What is the difference between cytokinesis in animal and plant cells?

A

In animals, a cleavage furrow forms in the middle of the cell and the surface membrane is pulled inwards by the cytoskeleton until it fuses in the middle (formed by crintavtion of a ring made of actin and myosin)

Where’s as in plants, due to their cell wall cleavage furrow cannot form, so vesicles are produced at the Golgi and assemble at the metaphase plate and fuse forming a new surface membrane and the new sections of cell wall form along this

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14
Q

What are the uses of mitosis?

A

To make new cells for growth, repair of tissue and asexual reproduction

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15
Q

When does crossing over occur and what is it?

A

In prophase 1 of meiosis

It is when homologous chromosomes pair up and get tangled, they swap sections of their dna - alleles of the same gene at a point called the chiasmata

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16
Q

When does independent assortment occur and what is it?

A

The orientation in which chromosomes or homologous pairs line in in mitosis which influences which cell daughter cell they go to and which alleles they give to that cell
As they are different due to crossing over

Happens in metaphase 1 and 2

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17
Q

What are 3 adaptions of erythrocytes and why?

A

Flattened biconcave disc shape- large SA:V

No nuclei- larger volume for lots of haemaglobin

Flexible- can fit through small capillarys

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18
Q

What are adaptions of neutrophils?

A

Multilobed nucleus- squeeze through gaps

Granular cytoplasm that contains many lysosomes to attack pathogens

19
Q

What are adaptations of squamous epithelial tissue?

A

The cells are flattened and thin

It is only 1 cell thick

= short diffusion pathway

20
Q

What are the adaptions of ciliates epithelial tissue?

A

Epithelial cells have Cilia to waft mucus up to oesophagus

Goblet cell secretes mucus to trap bacteria

21
Q

Adaptions of sperm cells?

A

Flagellum for movement
Mitochondria for energy
Acrosome which contains digestive enzymes to digest protective layers of the ovum

22
Q

Palisade cell adaptations

A

Contain chloroplasts to absorb light

Regular box shapes so can stack to form continuous layer

Thin cell walls for faster co2 diffusion

Large vacuole to maintain turgor pressure

23
Q

Root hair cell adaptations?

A

Surface of roots near growing tips

Long extension to increase surface area

lots of mitochondria for production of ATP used in active transport of ions across membrane

24
Q

Guard cell adaptations

A

One cell wall thicker than other so when turgid, changes shape she opens stomata, when flaccid closes stomata to reduce water loss

25
Q

Cartilage adaptations

A

Made of specialised cells called Chondrocytes that produce an extra cellular matrix made of collagen and elastin fibres

26
Q

Adaptions of muscle tissue?

A

Muscle fibres form fascicles which groups of form muscle they contain protein myofiliments called actin and myosin to form myofibrils

27
Q

What are totipotent stem cells?

A

Can differentiate into anything

Fertilised egg cell
Zygote

28
Q

What are pluripotent stem cells?

A

Can form all tissue types but not a whole organism

Eg embryonic stem cells

29
Q

What are multipotent stem cell?

A

Can form a range of cells within a certain type of tissue

30
Q

Where do the stems come from that can differentiate into erythrocytes and neutrophils?

A

Bone marrow

31
Q

Where are the stem cells for xylem and phloem found?

A

The meristems

32
Q

How can you treat Alzheimer’s with stem cells?

A

Growing stem cells into nerve cells

33
Q

How can you treat Parkinson’s disease with stem cells?

A

Replace dopamine producing brain cells which have died

34
Q

what happens if a cell doesnt meet the requirements at a checkpoint in the cell cycle?

A

the cell cycle doesnt proceed until the damage is repaired or goes to G0

35
Q

where is meristematic tissue found?

A

in the tips of roots and shoots and in the cambium

36
Q

what is developmental biology?

A

the study of changes that occur as multicellular organisms griw abd develop from a single cell and why things can go wrong

37
Q

what is the cell wall of bacteria made from?

A

peptidoglycan

38
Q

discuss the ways in which genetic variation is produced

A

A1 independent assortment / random segregation ,
of (homologous) chromosomes / bivalents;
A2 in , metaphase I / meiosis I ;
A3 of chromatids in , metaphase I I / meiosis I I ;
A4 (so) homologous chromosomes , have different
alleles / come from different parents ;
A5 produces large number of allele combinations ;
C1 crossing over / (formation of) chiasma(ta) ;
C2 in , prophase I / meiosis I ;
C3 (so) chromatids will have new combination of alleles ;
C4 amount of variation depends on distance between
crossover points ;
M1 mutation ;
M2 changes the (DNA) nucleotide/ base, sequence ;
M3 DNA checks (during duplication)
did not recognise damage ;
M4 idea of differences in (named) protein(s) ;
N1 non-disjunction ;
N2 homologous chromosomes do not separate
(in metaphase I) ;
N3 one , more / less , chromosome present ;
F1 random, mating / fusion of gametes/ fertilisation ;
F2 gametes are not genetically identical;
F3 produces large number of (allele) combinations ;

39
Q

why does mieosis need twice as many stages as mitosis?

A

to, halve chromosome number / reduce from 2n to n ;
to separate homologous pairs (of chromosomes)
and sister chromatids ;
because, DNA (previously) replicated /
chromosomes are two chromatids at start ;

40
Q

describe asexual reproduction in yeast

A

mitosis ;
swelling / bulge, in (surface of) the cell ;
nucleus moves into, swelling / bulge / bud ;
idea that, bulge / bud, nips / pinches / breaks off / cleaves ;
ref to uneven distribution of cytoplasm ;

41
Q

) Before the division of the nucleus of a cell, the genetic material must replicate.
Explain why this is essential.

A

so that daughter cells have all the identical genetic material

42
Q

what is a homologous pair?

A 
1 one maternal and one paternal / AW ;
2 carry same genes ;
3 carry, same / different, alleles ;
4 (usually) same / similar, length ;
5 centromere in same position ;
6 same banding pattern ;
7 pair up in meiosis / form bivalent ;
43
Q

What is formed when two gametes fuse at fertilisation?

A

Zygote

44
Q

Why specialised cells unable to undergo mitosis?

A

have already differentiated so cannot divide

are in , G0 (phase of cell cycle) / resting phase

idea that shape is (too) , irregular

cytoskeleton cannot function / spindle (fibres)
cannot form

Biology OCR A Alevel (26 decks)

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