Cell Devision Flashcards
What stages are within interphase?
G1, S, G2
What takes place in G1?
Protein synthesis of proteins that synthesise organelles
Organelle replication
Cell growth
What takes place in the S phase?
Dna replication
What takes place in g2?
Energy stores increased
Duplicated dna checked for errors
Cell growth
What are the 3 checkpoints of the cell cycle?
G1 check point
G2 checkpoint
Spindle assembly checkpoint
What is checked for in the g1 checkpoint?
Cell size
Nutrients
Growth factors
Dna damage
once satisfied DNA replication is triggered
What is checked for in the G2 checkpoint?
Cell size
Dna replication
Dna damage
once satisfied the cell initiates molecular processes that signal the start of mitosis
What is checked for and when does the spindle assembly checkpoint occur?
Check chromosomes are attached to spindles
Occurs in metaphase before it can proceed to anaphase
What happens in prophase of mitosis?
Chromatin fibres cool and condense to form chromosomes
Nucleolus disappears and nuclear envelope breaks down
Centrioles migrate to poles which aids Spindles assemble
What happens in metaphase or mitosis?
Chromosomes are moved to the metaphase plate by spindle fibres
What happens in anaphase of mitosis?
Centromeres divide
Chromatids separate and are moved to opposite poles by contracting spindle fibres
What happens in telophase of mitosis?
Nuclear membrane reforms and chromosomes uncoil to chromatin and cytokinesis begins`
What is the difference between cytokinesis in animal and plant cells?
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
What are the uses of mitosis?
To make new cells for growth, repair of tissue and asexual reproduction
When does crossing over occur and what is it?
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
When does independent assortment occur and what is it?
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
What are 3 adaptions of erythrocytes and why?
Flattened biconcave disc shape- large SA:V
No nuclei- larger volume for lots of haemaglobin
Flexible- can fit through small capillarys
What are adaptions of neutrophils?
Multilobed nucleus- squeeze through gaps
Granular cytoplasm that contains many lysosomes to attack pathogens
What are adaptations of squamous epithelial tissue?
The cells are flattened and thin
It is only 1 cell thick
= short diffusion pathway
What are the adaptions of ciliates epithelial tissue?
Epithelial cells have Cilia to waft mucus up to oesophagus
Goblet cell secretes mucus to trap bacteria
Adaptions of sperm cells?
Flagellum for movement
Mitochondria for energy
Acrosome which contains digestive enzymes to digest protective layers of the ovum
Palisade cell adaptations
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
Root hair cell adaptations?
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
Guard cell adaptations
One cell wall thicker than other so when turgid, changes shape she opens stomata, when flaccid closes stomata to reduce water loss
Cartilage adaptations
Made of specialised cells called Chondrocytes that produce an extra cellular matrix made of collagen and elastin fibres
Adaptions of muscle tissue?
Muscle fibres form fascicles which groups of form muscle they contain protein myofiliments called actin and myosin to form myofibrils
What are totipotent stem cells?
Can differentiate into anything
Fertilised egg cell
Zygote
What are pluripotent stem cells?
Can form all tissue types but not a whole organism
Eg embryonic stem cells
What are multipotent stem cell?
Can form a range of cells within a certain type of tissue
Where do the stems come from that can differentiate into erythrocytes and neutrophils?
Bone marrow
Where are the stem cells for xylem and phloem found?
The meristems
How can you treat Alzheimer’s with stem cells?
Growing stem cells into nerve cells
How can you treat Parkinson’s disease with stem cells?
Replace dopamine producing brain cells which have died
what happens if a cell doesnt meet the requirements at a checkpoint in the cell cycle?
the cell cycle doesnt proceed until the damage is repaired or goes to G0
where is meristematic tissue found?
in the tips of roots and shoots and in the cambium
what is developmental biology?
the study of changes that occur as multicellular organisms griw abd develop from a single cell and why things can go wrong
what is the cell wall of bacteria made from?
peptidoglycan
discuss the ways in which genetic variation is produced
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 ;
why does mieosis need twice as many stages as mitosis?
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 ;
describe asexual reproduction in yeast
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 ;
) Before the division of the nucleus of a cell, the genetic material must replicate.
Explain why this is essential.
so that daughter cells have all the identical genetic material
what is a homologous pair?
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 ;
What is formed when two gametes fuse at fertilisation?
Zygote
Why specialised cells unable to undergo mitosis?
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
