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Cell1001 > lecture 1 > Flashcards

lecture 1 Flashcards

1
Q

What is embryogenesis

A

the formation of a multicellular organism

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2
Q

what are the stages of development after fertilisation

A 
cleavage
gastrulation
neurulation
organogenesis
metamorphosis
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3
Q

name the 6 model organism Dale mentioned

A 
Mouse (mus muculus)
chick (gallus gallus)
Frog (xenopus laevis)
Zebrafish (danio rerio)
fruitfly (drosophila melanogastor)
nematode worm (c. elegans)
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4
Q

what are the HOX genes involved in

A

Anterior to posterior patterning

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5
Q

what does PAX6 do?

A

involved in eye development

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6
Q

what is the function of chordin

A

Neural development

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7
Q

are female gametes formed in meiosis equal?

A

No. single ovum and two smaller polar bodies

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8
Q

in the amphibian egg what % is yolk protein

A

90%

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9
Q

What are the 4 Types of egg

A

Isolecithal
mesolecithal
telolecithal
centrolecithal

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10
Q

which organism forms isolecithal eggs? what are the main features

A

Mammals and C. elegans. small egg with little yolk evenly distributed throughout cell

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11
Q

which organism form mesolecithal egg

A

Amphibians. large eggs, large amounts of yolk but only localised to one half of the egg vegetal hemisphere lightly pigment

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12
Q

which organisms form telolecithal eggs

A

Fish Reptiles Birds. moderate to large amounts of yolk throughout cellexcept at pole

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13
Q

which organisms form centrolecithal eggs

A

arthropods and insects. yolk concentrated to centre of egg, periphery yolk free

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14
Q

where is the RNA and mRNA in egg synthesised

A

synthesised by oocyte itself

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15
Q

what are the two hemispheres that make up egg

A

Animal and vegetal

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16
Q

what is in the animal hemisphere?

A

presence of egg nucleus- germinal vesicle

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17
Q

whats in vegetal hemisphere

A

mostly yolk

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18
Q

where do insects hold eggs before ovulation

A

metaphase 1

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19
Q

where are mammalian eggs held

A

prophase 1 before ovulation and metaphase 2 II until fertilisation

20
Q

what is a sperm made up of

A

Head-haploid nucleus centrosome, acrosome
midpeice- mitochondria, base of flagellum
tail- flagellum

many sperm abnormal (2 heads or 2 tails)

21
Q

what is parthenogenesis

A

ability of some species to develop without sperm (some mice have been created -in lab i think)

22
Q

what are gynomorphs and andromorphs

A

i dont know

23
Q

what is a hydatiform mole? and what is it caused by?

A

when trophoblast cells of placenta form grape like cyst when fertilised. either caused by loss of female chromosome in meiosis or by polyspermy

24
Q

what is Genetic imprinting?

A

altering the dna and associated histone protein to only express 1 version of the gene. inactivates other copies

25
Q

what is parental conflict theory

A

different imprinting due to interest of each parent in terms of evolutionary fitness

26
Q

where does the sperm reach the egg

A

the ampulla region of fallopian tube

27
Q

what is the egg surrounded by?

A

in mammals- zona pellucida, in other animals vitelline

28
Q

what stops cross species fertilisation?

A

on the outside of the egg is a specific sperm detector (in mice ZP3- without it, infertile)

29
Q

what causes the acrosome reaction to start?

A

the sperm coming into contact with zona pellucida

30
Q

describe the acrosome reaction

A

enzymes are released from the acrosome that digest a hole in the zona pellucida for sperm to go through. the sperm then fuses with the plasma membrane and increases cytoplasmic Ca2+ which causes the cortical reaction.

31
Q

what is the cortical reaction?

A

increased Ca2+ cortical granules bind with plasma membrane and they release their contents into extra cellular space. modifies sperm receptors to prevent poly spermy.

32
Q

how do other organisms stop polyspermy

A

many species reverse the charge of the membrane- this is quicker than the cortical reaction

33
Q

What is Cleavage?

A

rapid cell division without cell growth, forming progressively smaller blastomeres

34
Q

what is cytokinesis driven by?

A

contractile ring of actin and myosin along same equator as the chromosomes line up upon

35
Q

why does the first cleavage take longest?

A

because time is needed for the two haploid nuclei to find each other and line up

36
Q

what are the cleavage rates for several animals

A

Drosophila: 8mins
C. elegans: 20 -40 mins
Zebrafish: 15-20 mins
Xenopus laevis: 25- 30mins

37
Q

why is cell cycle so short compared to adults?

A

cell cycle only includes S and M all gap phases are deleted. S phase is modified so that it is faster

38
Q

are there gap phases in mammalian cleavage

A

yes it cell cycle is slower in mammals than other organisms

39
Q

what controls the cell cycle

A

the cell cycle is controlled by the ratio of DNA to cytoplasm

40
Q

what are the two types of cleavage?

A

holoblastic and meroblastic

41
Q

what is meant by holoblastic cleavage

A

found in isolecithal and mesolecithal eggs it is complete cleavage

42
Q

meroblastic cleavage is…

A

incomplete cleavage in telolecithal and centrolecithal eggs. only a portion of the egg is cleaved. in insects male sand female nuclei fuse, 9 nuclei are formed after 3 nuclear divisions, move to the edge of cells. memebrane forms

43
Q

what happens in compaction

A

outer layer forms epithelium of tropoblast cells. these pump Na+ into extra cellular space in centre of embryo ater follow. blastocoel formed. inner cell mass forms. embryo called a blastocyst

44
Q

when are gaps added in amphibian cell cycle

A

at the mid blastula phase

45
Q

what must happen in order for different cells to be formed

A

genome must be transcribed.

Cell1001 (2 decks)

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