BIOL 102 Exam 2

BIOL 102 Exam 2

Why is asexual reproduction involving mitosis and cytokinesis even maintained as a reproductive like strategy?

Asexual reproduction allows for rapid population growth in fewer generations than sexual reproduction

When would asexual reproduction be more advantageous than sexual reproduction?

In stable environments where adaptation is less necessary. Asexual reproduction does not require the energy of finding a mate.

What does the “cost of males” model hypothesize?

sexual reproduction is disadvantageous because sexual females invest roughly half of their resources into producing sons, which do not directly bear offspring, whereas asexual females produce only daughters

What does the “cost of males” model imply about sexual reproduction (broadly - think why do we see both phenomena in the modern world)?

in order for sexual reproduction to persist, there must be a benefit that arises. Increase in fitness relative to asexual reproduction is seen as this benefit.

What is a major way that sexual reproduction/meiosis results in an increase in fitness?

the increase in genetic diversity associated with sexual reproduction/meiosis

In a mitotic world, X individuals produce X offspring and Y individuals produce Y offspring (clones) with no difference between parents and offspring unless ______ arise.

mutations

Suppose in an X individual, a beneficial mutation arises in Gene A. In a Y individual, a beneficial mutation arises in Gene B. Through mitosis alone, can these beneficial mutations be shared?

no

In a purely mitotic scenario, suppose in an X individual, a beneficial mutation arises in Gene A. In a Y individual, a beneficial mutation arises in Gene B. How could these mutations be “combined”?

If the X and Y lineages develop a second mutation matching the other lineage’s first mutation.

What quote is the “Red Queen Hypothesis” based on?

“…it takes all the running you can do to stay in the same place…”

The Red Queen Hypothesis suggests that species must constantly evolve simply to survive against ever-evolving opposing organisms. What specific phenomenon characterizes this continuous, reciprocal struggle for ecological advantage through a succession of adaptations and counter-adaptations?

co-evolutionary arms race

Through sexual reproduction, organisms generate genetic variation more quickly than through ________ ________, and thus they can track their changing abiotic and biotic ________ most effectively.

asexual reproduction, environments, effectively

What are gonads?

Organs that produce gametes (testis or ovaries)

In the Curtis lively experiment 1, higher infection rates between snails and parasites from the same lake were discovered. What did this suggest about the parasites from the two lakes?

parasites are locally adapted to feeding on snails in their same lake

What is a genetic marker?

a specific region of DNA, often located within or near a gene, that is different (variable) enough to allow scientists to distinguish between different organisms

In the Curtis lively experiment 2, “rare genotype snails” observed a lower rate of infection than “common genotype snails.” What could this infer regarding rare genotype snails and the parasites?

Rare genotype snails have a combination of genes (“rare genes”) that enable them to mount defense against parasites and/or the parasites can’t infect them as well.

Sexual reproduction is associated with the potential for increases in _____ _____, ______, and ________.

genetic mixing, variation, diversity

We assume that rare genotypes (by chance) will arise more likely with _______ reproduction.

Sexual

sex may be advantageous because it generates _______ ________ in heterogeneous, novel, or changing environments

beneficial mutationses

sex may reduce or prevent an increase of ______ ____, which results in the removal of deleterious mutations

mutational load

sex may reduce or prevent an increase of mutational load, which results in the removal of _______ ________

deleterious mutations

Viruses infect eukaryotes, _____ infect bacteria

phage

Why did Lin Chao study phage?

phage have rapid generation time, rapid mutation rate, and the genetic material of phage can undergo recombination

What is the lytic life cycle of bacteriophage?

Phage attaches to a bacterial cell

Phage injects genetic material into cell

Use host to make proteins etc. to translate their genetic material into phage protein (they use the host’s machinery)

Translated genetic material form phage progeny and bacterial cell lyses (dies)

Phage progeny release

In experiments with phage, one common technique uses bacteria that has been grown on an ____ ____

agar plate

In a lawn of bacteria on an agar plate, clear regions are called ______

plaques

Plaques signify that phage in that region ______ ________

killed bacteria

In a plaque, all phage are _____

clones

What is the process of combining liquid phage culture with liquid bacteria called?

Innoculation

after mixing bacterial and phage cultures, a _____ is used to separate bacteria and phage

filter

It is critical to remember that one phage can infect a bacterial host cell but also ___ phage can infect the same host

two

How is the phenomenon of two phage infecting one bacterial host controlled for in lab?

altering concentrations of phage and bacteria

______ concentrations of phage increase the chance that more than one phage will infect a bacterial host cell

higher

What were Lin Chao’s experiments designed to address?

the idea of “Muller’s Ratchet”

What is Muller’s Ratchet?

The idea that deleterious mutations accumulate over time and if they do accumulate, fitness will decrease.

According to Muller’s Ratchet, sexual reproduction plays a critical role, permitting an “escape” from the ratchet, since it would lead to a decrease in ______ ____

mutational load

Each plaque is the result of ___ infectious phage

one

Why is low-concentrations of phage used when plating onto a lawn of bacteria?

This helps ensure that the plaques are areas where only one phage killed the bacteria in that region

What was group A considered in Lin Chao’s experiment 1?

Group A was considered the “sexual” group

What was group B considered in Lin Chao’s experiment 1?

Group B was considered the “asexual” group

In experiment 1, what concentration of phage was initially used to inoculate the bacterial culture?

high concentration

In experiment 1, what concentration of phage was initially used to infect the lawn of bacteria?

low concentration

Why was group B considered as if it was going through a “bottleneck”?

The experiment was forcing the phage through the bottleneck of 1 genetic type each cycle.

What was the result of experiment 1?

Phage from the “sexual” group always produced more phage progeny

What was the interpretation of the result of experiment 1?

the fitness of “Asexual” group B is poor because deleterious mutations are accumulating

What did experiment 2 aim to address?

Whether the “asexual” group can be rescued from the ratchet

What was the starting phage in experiment 2? concentration?

Phage from the experiment 1 “asexual” group. Began with low concentration

What was the procedure of experiment 2?

After plating the “asexual” phage onto a bacterial lawn, two plaques were chosen (not necessarily identical), and they were placed into liquid culture. Both concentrations of phage (both high) were used to inoculate a bacterial culture and were then filtered out. This was repeated many times.

What was the result of experiment 2?

Group B “asexual” phage from experiment 1 “regained fitness.” This assumes their fitness was comparable to the “sexual group".”

What was the interpretation of the result of experiment 2?

Reshuffling of genetic material due to recombination results in increased fitness

What did Experiment 3 aim to explore?

The effects of beneficial mutations

What phage were used to start with in experiment 3?

Group B “asexual” group (low conc)

What was the procedure of experiment 3?

After plating the “asexual” phage onto a bacterial lawn, one plaque was chosen, and phage were placed into liquid culture and used to inoculate a bacterial culture and were then filtered out. This was repeated many times. This allowed phage to evolve freely with no bottleneck.

What was the result of experiment 3?

Relative to group B “asexual” phage from experiment 1, there was a 21% increase in fitness

What was the interpretation of the result of experiment 3?

Accumulation of beneficial mutations is possible, as indicated by 21% increase in fitness relative to bottlenecked asexual phage in experiment 1.

What two groups were used to start experiment 4?

High concentration of phage from experiment 3 and high concentration of phage from experiment 1 A “sexual” group.

What was done in experiment 4?

The two phage groups (freely evolved phage from experiment 3, sexual phage from experiment 1) were inoculated into one bacterial culture, then separated out with a filter, and this repeated many times.

What was the result of experiment 4?

There was a 9% increase in fitness relative to experiment 3.

What was the interpretation of the result of experiment 4?

The 9% increase in fitness is due to reshuffling of genetic material via recombination (“sex”).

Define gametogenesis

generation of gametes

what is spermatogenesis? ____ gametogenesis

male

what is oogenesis? _______ gametogenesis

female

What are the two design criteria of gametes?

1) have to be numerous enough that they can find another gamete with high to unite

2) have to be large enough to provide resources for the embryo during early stages of development

Anisogamy is the existence of two different _________, both specialized cells, and each meets ___ design criteria.

gametes, one

Sperm are small, ____, and _____ (cheap)

mobile, expendable

Sperms are essentially packets of DNA with _______

propulsion

Do sperms have a lot of cytoplasm?

no

Sperms have a ____ nucleus and an ________ vesicle

haploid, acrosomal

What critical function does actin protein serve?

Extension of the acrosomal process during early stages of fertilization

sperm = spermozoa = ___ ____

sperm cells

Sperm are adapted to deliver _____ to the ___

DNA, egg

The final stage of spermatogenesis is called _______

spermiogenesis

what is a spermatid?

Immature male gamete

What do spermatids undergo?

spermiogenesis

During spermiogenesis, what do spermatids undergo?

cellular and nuclear reshaping, organelle reorganization, tail formation

What is the mature male gamete?

spermatozoa

How big is the egg?

120 micro meters or 0.12mm

Is the egg cytoplasm large?

yes

The cytoplasm of the egg serves as a “storehouse” for many molecules, including….?

proteins, enzymes, ribosomes, mRNA, organelles, etc.

The egg contains all material / resources necessary for ______ ________ during the early developmental stages

Embryo development

What is the egg nucleus

1N

What is the jelly coat around the egg made of? and where is it located next to?

Polysaccharides, located right next to vitellin envelope

Egg envelope / vitelline envelope forms a fibrous mat, containing many …..

proteins and glycoproteins

How is the egg envelope attached to the plasma membrane?

protein tethers

What does the initial meiosis 1 and 2 of spermatogenesis produce?

4 haploid spermatids

What happens in meiosis 1 of oogenesis?

unequal cytokinesis and the production of the first polar body

What does oogenesis produce and what happens to each product after both divisions in meiosis occur?

Oogenesis produces one large cell and three polar bodies. The large cell becomes the mature ovum and the polar bodies degenerate.

What is symgamy?

fusion of gametes

What are the two challenges of the fertilization process?

1) species specific fertilization

2) avoiding polyspermy

What are the two mechanistic strategies related to species specific fertilization?

behavioral and molecular

What are examples of behavioral mechanisms to prevent species-specific fertilization?

Courtship, dance, color, mate recognition

What is chemotaxis?

The egg releases factor, sperm swim towards highest concentration of faster, so sperm follows a gradient of the factor (toward the egg)

What is species specific activation? “sperm activation” “acrosome reaction”

Egg jelly has species-specific activation factors - causes changes in sperm - results in fertilization

Egg jelly has factors called ______ that interact with sperm via cell membrane receptors

glycoproteins

Binding of sperm with glycoprotein leads to opening of Ca channels and this permits Ca to enter spearhead resulting in ______ _______

“acrosome reaction”

When sperm contacts egg jelly, glycoproteins in egg jelly bind to …

sperm cell membrane receptors

The acrosome reaction is the fusion of the ______ _____ with the ___ ___ _______

acrosomal vescicle, sperm cell membrane

The exocytosis reaction is when the acrosomal vesicle fuses with sperm cell membrane and…

acrosomal vescicale contents are released (mediated by Ca)

The AV releases enzymes that ___ ____ ___, creating a path to the egg surface.

digest egg jelly

Step 2 of the acrosome reaction is…

extension of the acrosomal process