Vertebrate Development

Question 1

Fertilization, Cleavage, Gastrulation, then what?

Answer 1

Phylotypic Stage (Distinct head)

Question 2

Phylotypic Stage

Answer 2

1. Forms the distinct head
2. Neural Tube is formed (place where future brain & nervous system will be
3. Notochord- place where future spine will be, flanked by somites (which are blocks of cells for future muscle & skeleton)

Question 3

Anamniotes

Answer 3

No amnion, fish and amphibians

Question 4

Amniotes

Answer 4

Amnion- extra embryonic membrane (mammals & birds)

Question 5

Frog (Xenopus)

Answer 5

1. Have easy access to zygotes where can inject hormones to make them mate
2. They have 100 eggs in one large blastula (which is easy to manipulate)
3. They are hardy eggs where no infections after surgery

Question 6

Which is better for genetic studies X. tropicalis (diploid) or X. laevis?

Answer 6

X. tropicalis which is diploid

Question 7

Frog life cycle: The egg

Answer 7

1. Polar where it has two region a dark region that is the animal region & a light region that is vegetal region (yolk/proteins)
2. Stopped at meiosis - 1
3. Fertilization- one sperm enters the animal region where it starts meiosis 2 & pronuclei fuse

Question 8

What happens during the 1st cleavage of a frog egg?

Answer 8

1st cleavage occurs 90 mins after fertilization through animal- vegetal axis where it cuts both animal & vegetal region

Question 9

2nd Cleavage of frog egg

Answer 9

Occurs after 30 mins where it cuts through animal- vegetal axis perpendicular to the 1st cleavage where it cuts both animal & vegetal region (all cells are equivalent)

Question 10

3rd cleavage

Answer 10

Occurs at the equatorial axis where it separates the animal & vegetal region- 4 small animal cells & 4 large vegetal cells (both blastomeres)

Question 11

Cleavage of the frog eggs

Answer 11

Its synchronous initially but at 4th division, not synchronous where thick vegetal yolk impedes which results in the vegetal region having fewer but larger cells

Question 12

Blastula

Answer 12

Occurs after the 12th cleavage where it has 1,000 cells& in the animal region the blastocoel is the fluid cavity (the 3-germ layer are allocated but not moved)

Question 13

Gastrulation

Answer 13

1. Has a little mitosis where it moves & rearrangement of germ layers
2. blastopore –infoldings on future dorsal side
3. dorsal lip–organizer of AP axis structures

Question 14

Gastrulation also involves what during the frog egg cycle?

Answer 14

1. involution- endoderm, mesoderm occurs where they move inside through blastopore
2. epiboly- ectoderm spreads & covers embryo

Question 15

Neurulation (neurula)

Answer 15

Occurs after fertilization where the neutral tube precursor to CNS

Question 16

Organogenesis

Answer 16

Involves making organs & tissues

Question 17

Describe the frog egg cycle

Answer 17

1. Egg goes through cleavage to make blastula
2. Blastula goes through gastrulation to make gastrula
3. Gastrula makes neurula
4. Neurula goes through Organogenesis to make an embryo
5. Embryo forms tadpole
6. Tadpole goes through metamorphosis to become an adult

Question 18

Zebrafish

Answer 18

1. Has a short life cycle off about 3 months
2. Embryo transparent
3. Cleavage doesn’t cut through the yolk instead the blastomeres mound on top of the yolk

Question 19

Mutation involving zebra fish

Answer 19

lymphatic vessels grow out of control fluid accumulation in lungs (created same mutation in zebrafish fish got similar phenotypes screened for drugs saved boy’s life)

Question 20

Early studies

Answer 20

Were descriptive where they describe & draw & used microscopes

Question 21

In situ hybridization

Answer 21

They detect mRNA gene expression with labeled RNA probe where the whole embryo in situ

Question 22

Immunofluorescence

Answer 22

Detect protein gene expression with labeled antibody

Question 23

Microinjection (Used for fate mapping)

Answer 23

1. Use for large cells
2. Fluorescent dye
3. GFP mRNA

Question 24

Forward genetics

Answer 24

Phenotype can be used to ID genes, it also has spontaneous mutations, which are slow rate & natural Induced mutations, which are forced & high rate (like chemicals, X-ray, UV)

Question 25

Induced mutations

Answer 25

Random mutations that can occur in every gene & can also treat large populations (breed fast)

Question 26

Zebrafish relating to mutation

Answer 26

1. Large-scale mutagenesis 2. high fecundity many embryos 3. embryo transparent - large ID phenotype

Question 27

Induced mutations (with mice)

Answer 27

Dominant mutants were shown in the phenotype of F1 (F1 shows phenotype)

Question 28

Induced mutations in fish

Answer 28

Recessive mutants phenotype in F3 (F1 het. (no phenotype), F2 het fam (no phenotype), when you cross F2 fam, F3 homo recessive (phenotype)

Question 29

Knock-out

Answer 29

1. permanent germline | 2. mutate gene in ESCs in vitro

Question 30

Knock-in

Answer 30

1. knock-out | 2. replace endogenous gene (or allele) with another

Question 31

Knock-down

Answer 31

1. block mRNA or protein not DNA | 2. transient DNA intact (RNAi)