lecture 1

Question 1

What is embryogenesis

Answer 1

the formation of a multicellular organism

Question 2

what are the stages of development after fertilisation

Answer 2

cleavage
gastrulation
neurulation
organogenesis
metamorphosis

Question 3

name the 6 model organism Dale mentioned

Answer 3

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

Question 4

what are the HOX genes involved in

Answer 4

Anterior to posterior patterning

Question 5

what does PAX6 do?

Answer 5

involved in eye development

Question 6

what is the function of chordin

Answer 6

Neural development

Question 7

are female gametes formed in meiosis equal?

Answer 7

No. single ovum and two smaller polar bodies

Question 8

in the amphibian egg what % is yolk protein

Answer 8

90%

Question 9

What are the 4 Types of egg

Answer 9

Isolecithal
mesolecithal
telolecithal
centrolecithal

Question 10

which organism forms isolecithal eggs? what are the main features

Answer 10

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

Question 11

which organism form mesolecithal egg

Answer 11

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

Question 12

which organisms form telolecithal eggs

Answer 12

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

Question 13

which organisms form centrolecithal eggs

Answer 13

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

Question 14

where is the RNA and mRNA in egg synthesised

Answer 14

synthesised by oocyte itself

Question 15

what are the two hemispheres that make up egg

Answer 15

Animal and vegetal

Question 16

what is in the animal hemisphere?

Answer 16

presence of egg nucleus- germinal vesicle

Question 17

whats in vegetal hemisphere

Answer 17

mostly yolk

Question 18

where do insects hold eggs before ovulation

Answer 18

metaphase 1

Question 19

where are mammalian eggs held

Answer 19

prophase 1 before ovulation and metaphase 2 II until fertilisation

Question 20

what is a sperm made up of

Answer 20

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

many sperm abnormal (2 heads or 2 tails)

Question 21

what is parthenogenesis

Answer 21

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

Question 22

what are gynomorphs and andromorphs

Answer 22

i dont know

Question 23

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

Answer 23

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

Question 24

what is Genetic imprinting?

Answer 24

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

Question 25

what is parental conflict theory

Answer 25

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

Question 26

where does the sperm reach the egg

Answer 26

the ampulla region of fallopian tube

Question 27

what is the egg surrounded by?

Answer 27

in mammals- zona pellucida, in other animals vitelline

Question 28

what stops cross species fertilisation?

Answer 28

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

Question 29

what causes the acrosome reaction to start?

Answer 29

the sperm coming into contact with zona pellucida

Question 30

describe the acrosome reaction

Answer 30

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.

Question 31

what is the cortical reaction?

Answer 31

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

Question 32

how do other organisms stop polyspermy

Answer 32

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

Question 33

What is Cleavage?

Answer 33

rapid cell division without cell growth, forming progressively smaller blastomeres

Question 34

what is cytokinesis driven by?

Answer 34

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

Question 35

why does the first cleavage take longest?

Answer 35

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

Question 36

what are the cleavage rates for several animals

Answer 36

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

Question 37

why is cell cycle so short compared to adults?

Answer 37

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

Question 38

are there gap phases in mammalian cleavage

Answer 38

yes it cell cycle is slower in mammals than other organisms

Question 39

what controls the cell cycle

Answer 39

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

Question 40

what are the two types of cleavage?

Answer 40

holoblastic and meroblastic

Question 41

what is meant by holoblastic cleavage

Answer 41

found in isolecithal and mesolecithal eggs it is complete cleavage

Question 42

meroblastic cleavage is...

Answer 42

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

Question 43

what happens in compaction

Answer 43

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

Question 44

when are gaps added in amphibian cell cycle

Answer 44

at the mid blastula phase

Question 45

what must happen in order for different cells to be formed

Answer 45

genome must be transcribed.