Purdue Bio 111 Lab Practical 2

How does gastrulation in echinoderms, amphibians, and birds compare?

Echinoderm gastrulation is like the classic pushing in the leaky tennis ball: an invagination from the vegetal pole into the blastocoel.

Amphibian gastrulation is an involution of cells just ventral to where the gray crescent was located in the zygote; this inward movement continues as cells of the animal hemisphere migrate down over the larger yolky cells of the vegetal hemisphere.

Bird gastrulation is in two steps: a lower layer of blastodisc cells migrates away, forming a layer of hypoblast cells below the epiblast (which the remaining cells of the blastodisc are now known as). Then, as the hypoblast expands, the epiblast cells migrate rearwards and medially to form the primitive streak, through which streak cells migrate to form the mesoblast, a layer of cell between the epiblast and the hypoblast.

What are short life cycle plants called?

fast plants

What is the gene in question in the Analysis of Fast Plants Crosses lab?

the gene that controls the synthesis of a purple pigment called anthocyanin

what is the gene ANL?

the dominant gene that allows the purple pigmentation to appear

what is the gene anl?

the recessive gene

what happens if seedlings are homozygous anl?

they have yellow-green stems

what do the seeds represent?

the F1 generation

What test do you use to evaluate your predictions in the Fast plants lab?

Chi-test or X2

What is a test cross?

a mating in which one parent is homozygous at all loci of interest

What is crossing-over a form of?

recombination

what does recombination do?

produces gene combinations in the gamete of an organism that are different than the gene combinations that were in the gametes that fused to make that organism

what is the percent recombinant offspring?

a conservative estimate of the distance between loci

What is the distance between genes measured by?

map units or centimorgans (cM)

What is activation energy?

the energy that must be supplied before a reaction that involves covalent bonds will proceed

how can activation energy be reduced?

by a catalyst

enzymes are usually.....?

proteins (although some types of RNA have enzymatic activity)

what enzyme is investigated?

alkaline phosphatase

what substrate is used?

pNPP

the greater the concentration of pNP in solution the more blue light it absorbs

it has a higher absorbance

what does the monochromator in a spec 20 do?

splits light into various wavelength and then selects desired wavelength

independent variables for enzyme lab

enzyme concentration, initial substrate concentration, and pH

dependent variable for enzyme lab

initial rate of reaction

calibrating the spec 20

1. adjust spec 20 w/o tube to infinite absorbance on left end of bottom scale

2. adjust spec 20 w a blank so the spec 20 reads zero absorbance at bottom right of scale

what is the relationship between enzyme concentration and initial rate of reaction?

LINEAR; the more concentration, the higher the rate

What is the relationship between initial substrate concentration and initial reaction rate?

At first, the initial rate of reaction increases with increasing substrate concentration. Eventually, the initial rate levels off, even as substrate concentration increases. At these high pNPP concentrations the enzyme is saturated with substrate; when one pNPP molecule is broken down another is immediately available. The enzyme can only work so fast, adding more substrate will not accelerate the rate

What is the relationship between pH and initial reaction rate?

The curve indicates that there is a narrow range of pH where the reaction rate is highest. If the pH falls outside this range, the reaction rate is lower. This is probably due to changes in the enzyme's molecular shape or conformation brought about by changes in pH.

what does fertilization accomplish?

1. activating the oocyte so it goes on to complete development

2. provides the means by which the two haploid sets of chromosomes from the sperm and the egg can restore into diploid condition for the zygote

what is the fertilization membrane?

long-term mechanical barrier that helps to ensure the zygote will be diploid

polyspermy

entrance of more than one sperm into the egg

how will the sperm be recognized?

appear as tiny greenish spheres jiggling around

what causes the jiggling motion?

flagella

cleavage in a sea urchin is holoblastic

the cleavage furrows cut completely and quickly through the embryo

echinoderm polarity

nucleus is offset towards the animal pole

echinoderm cleavage

first cleavage is vertical, from animal to vegetal pole

second cleavage is still vertical but a right angle to the first

third cleavage is horizontal

echinoderms cleave radially

morula

sixteen blastomeres

how is cell division in cleavage different from regular cell division?

there is no cell growth as the cell divides

how does an embryo become a blastula?

the ball of cells forms a cavity called a blastocoel

how does gastrulation in echinoderms begin?

when a few cells of the vegetal plate detach and migrate to the interior of the embryo

(these cells become the mesoderm cells)

2nd phase of gastrulation in echinoderms?

vegetal plate buckles inwards and extends itself into the interior of the embryo, forming the endoderm that become the archenteron (primitive gut)

blastopore

original opening of the gastrula (becomes the anus of developing larva)

echinoderms are?

deuterosomes

What is the difference between an oocyte and an egg?

An oocyte becomes an egg when meiosis is complete

what is the difference between an egg and a zygote?

An egg becomes a zygote when fertilization is complete (when the nucleus becomes diploid)

What are the biochemical consequences of egg activation?

The rates of RNA and protein synthesis increase dramatically. Also, DNA is synthesized in anticipation of cell division.

What must happen to restore the diploid condition in echinoderms during fertilization?

The haploid egg and sperm nuclei must fuse to become the diploid zygote nucleus

What constitutes the ectoderm, the endoderm, and the mesoderm of the sea urchin embryo?

The ectoderm is the outer cell layer of the gastrula; the endoderm is the archenteron (primitive gut); the mesoderm consists of the primary mesenchyme cells that migrate into the blastocoel from the basal plate of the blastula as gastrulation begins (which form the skeleton), and secondary mesenchyme cells that migrate from the invaginating archenteron (which form muscle cells).

how much yolk do amphibians have?

moderate amounts

how much yolk do birds have?

huge amounts

what does the amount of yolk in an egg influence?

the way early development progresses w respect to cleavage patterns and morphogenesis

polarity in amphibians

in addition to the nucleus being offset toward the animal pole, there is more dense yolk in the vegetal hemisphere than in the animal hemisphere, and there is pigment on the surface of the animal hemisphere

polarity in birds

the nucleus is offset toward the animal pole, and there is very dense yolk in the vegetal hemisphere

cleavage in amphibians

holoblastic but slower at the vegetal pole

cleavage in birds

restricted to the animal pole, many vertical cleavages and eventually horizontal

How does the formation of the blastula in echinoderms, amphibians, and birds compare?

In echinoderms, the wall of the blastula is one-cell thick all around; the blastocoel forms so that it occupies the animal and vegetal hemispheres equally

In amphibians, the floor of the blastocoel is considerably thicker than the roof of the blastocoel and the blastocoel forms almost exclusively in the animal hemisphere of the blastula.

In birds, the blastocoel is a very narrow space underlying the blastodisc, sitting on an enormous amount of yolk.