Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology 369 > Week Six > Flashcards

Week Six Flashcards

1
Q

What is a primary sex ratio?

A

Sex ratio of zygotes (fertilized eggs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a secondary sex ratio?

A

Sex ratio at birth; modified by differential survival of males and females, selective abortion, cytoplasmic pathogens and so on.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a tertiary sex ratio?

A

Sex ratio at reproductive maturity.

- Modified by differences in survival between the sexes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is an operational sex ratio?

A

Ratio of reproductively available males : females
- The sex that invests most is assumed to be less available for further reproduction, forming the basis of the Bateman principles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Does selection act upon the individual or the group?

-What are the implications?

A

When one sex becomes more common than the other, the rarer sex becomes more valuable.
- A case of negative frequency dependence.
-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the average RS with even sex ratio?

What if there are twice as many females?

What if there were an excess of males?

A

The average reproductive success of a male is the same as a female when there is a 1:1 sex ratio.

  • Average male reproductive success is double the female’s.
  • Average female reproductive success is double the male’s.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

If female produces limited offspring, would a population of excess males, equal males, or excess females be the most productive?

A

A population with an excess of females would almost always be more productive than the opposite, or one with equal SR.

  • Selection pushes the ratio back to 1:1 whenever one sex becomes more common, by favouring the rarer sex.
  • Strong proof that the individual and its (selfish) genes, not groups are the targets of selection.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the Trivers-Willard Hypothesis?

A

Females should invest more into sons when in high condition; into daughters when resources are scarce.

  • Hinges on the variation in male RS being higher than variation in female RS: most daughters can breed but sons only succeed if they are very robust and competitive.
  • Evidence presented weak.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are two interpretations of the T-W hypothesis?

A
  1. When in good condition, a female should produce more male offspring.
  2. When in good condition, a female (or coparenting pair) should invest more in their sons than daughters.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What might a high condition be, and which offspring are produced?

A

Ex. during a breeding year when food is abundant.
- Good environment, low inbreeding.

Males are favored.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What might be a low condition, and which offspring are produced?

A

Where close relatives breed in small sub-populations (demes).

Females are favored.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does it mean when the V(men)/V(female) < 1 for fitness?

A

Variability of men is less than variability of females, which means that men are in lower numbers and have greater fitness.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What did Clutton-Brock et al. show with red deer?

A

Dominant females were found to produce significantly more sons than daughters.
-Results corroborated several times since; linked to sex-dependent egg implantation probability based upon blood sugar levels.

-Odd-toed Ungulate mammals (like horses and rhinos; cattle, pigs, deer) show TW predicted sex ratio biases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the Trivers-Willard effect in Contemporary humans: billionaires?

-Authors?

A

Study done by Cameron and Dalerum.

  • Male billionaires have larger families than female billionaires.
  • Billionaires also have more sons.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the results of TW experiment on Bimoba and Kisasa tribes?

A

29000 paricipants in nearly 2000 households.

Found a t-W sex ratio bias:

  • More daughters poor households
  • More sons in rich households & higher reproductive success.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do parasitoid wasps manipulate the sex ratio, and why?

A

Adjust sex by choosing to fertilize (or not) their eggs.
-Haplodiploidy means unfertilized eggs will grow up as males.

Mothers are able to adjust sex of egg based upon the size of host (more daughters in bigger hosts) in many species.
-Smaller males are the norm in arthropods; about 90% of species.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does Fujita et al. present evidence for regarding breastfeeding?

A

High social status mothers in Kenyan agropastoral villages produce richer breast milk for sons than daughters.

  • Mothers of lower socio-economic status produce richer breast milk for daughters than sons.

Evidence from great apes suggest long nursing time for male offspring. - Yet dominant females were found to produce significantly more sons than daughters; linked to sex-dependent egg implantation probability based upon blood sugar levels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens with T-W when there is large imbreeding?

A

Bill Hamilton noticed that many arthropods grow up with close relatives and mate with them (inbreed).

  • Wasps, mosquitoes, mites.
  • Animals that lay many eggs all in one place and mate at maturation.

SUCCESS OF GROUP = success of individual.

  • Favors female-bias in SR.
  • Brothers compete for resources with their sisters and with each other, which is inefficient.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How many daughters are produced in the mite Acarophenax?

A

14 daughter are produced with only one son who fertilizes all sisters and dies before dispersal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Are there any other sex-determining systems aside from chromosomes?

A

Environment-dependent sex determination is common in reptiles

  • Turtles, tortoises, terrapins, males = cool conditions.
  • Lizards & alligators, males = warm temps.

-Environmental determination of sex removes the need for sex chromosomes and eliminates the sexual conflict they generate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is sex-limited gene expression?

A

Genes that are present in both sexes of sexually reproducing species but are expressed only in one sex and remain ‘turned off’ in the other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the benefits to sex-limited gene expression?

A

It is a way to limit the damage caused by sexually-antagonistic genes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is a sex chromosome? How are they activated?

Are there any exceptions to the rule?

A
  1. A sex chromosome begins life as an autosome.
  2. The chromosome acquires a sex-determining function (ex. SRY in humans).
  3. Usually this leads to recombination-suppression.
  4. Selection operates to reduce/stop recombination @ sex-determining locus.
    - Reasons for this are not well understood, and a number of fish and reptile species have normal recombination around the SD locus.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the upsides to recombination-suppression of Y-chromosomes?

A

The sex-determining locus attracts male-benefit genes.

The lack of recombination ensures:

  • No mixing with the female genes on the homolog
  • Linkage of these genes & co-transmission
  • Chance to optimize male function.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are the downsides to recombination-suppression of Y-chromosomes
- Invites hitchiking, background selection and the ratchet. - Once recombination ceases, the Y is no longer able to repair itself. - Degeneration of the Y ensues via: - Non-repair - Accumulation of parasitic DNA (ex. transposons) - Much of the Y becomes repetitive sequence. - Can lead to the ultimate loss of the Y and movement of the SD locus to another chromosome, or its replacement by another SD locus.
26
How is the sex of drosophilia determined?
Drosophilia sex is not determined by Y, but rather the X count. - XXY = female (humans = Klinefelter male) - X0 = male (humans = Turner female)
27
What did Adam and Rice find regarding Y-chromosome polymorphisms in fruit flies?
There is an an adaptive phenotypic variation associated with the Y chromosome. Discovered an interaction between fitness of species (with any of the Y chromosomes) and their genetic background. -Some backgrounds improved the fitness when carrying the Y, while others decreased the fitness. COOL.
28
What was the experiment of Kutch and Fedorka? PRocedure and results?
They introgressed Y chromosomes from different wild D. melanogaster populations into a standard isogenic background. - There was an impact on immune gene expression pattern in males. - Y-chromosome influenced the ability of males to combat experimental inoculation with Seratia marcescens. D. melanogaster Y appears to be responsible for dimorphism in immune system.
29
What are characteristics of the human Y chromosome?
The human Y contains a limited number of genes. -Some balance X-linked functions, others involved in sperm building. - 7 genes in the pseudoautosomal region. - 70-300 genes in total (out of about 25000) in the human genome.
30
What is the phenotype of klinefelter syndrome and the associated genotype?
Frontal baldness is absent. - Tendency to grow fewer chest hairs. - Breast development - Female-type pubic hair pattern - Small testicular size. - Long arms and legs - Wide hips - Narrow shoulders - Poor beard growth -XXY
31
What is the phenotype of turner syndrome and the associated genotype?
Webbed neck Cubitus valgus Lymphedema
32
What would happen if Y is lost due to degeneration? (review, what causes degeneration??)
Males would not be lost. - Many species live without a Y - Many different sex determining systems.
33
What was revealed when the human Y chromosome was sequenced?
Palindromic sequences!!!!! - May allow DNA repair within chromosome - Gene conversion known between palindromes
34
When would the mtDNA be integrated more readily?
During historical war, Y usually gets killed off, while mtDNA integrates more readily.
35
What do the lemba claim to be their origin? | What would the evidence be?
Lemba claim a Jewish origin (as do several other African and Asian peoples) - If founded by male Jewish traders, then should show Semitic Y chromosome patterns. - Some accuracy to their claim: over 50% of Ys have sequence consistent with semitic origin.
36
Where did the Australian aboriginal populations come from? Evidence?
Recent phylogenetic analysis helps us understand the origin and history of Australian aboriginal populations. -Supports a single source population and ancient migration Refutes a recent auggestion of immigration from india 4-5000ya.
37
What is the Mitochondrial Eve?
The mt Eve is the common ancestor of all cytoplasmically-inherited features having an unbroken lineage. - She is estimated to have lived 150KYA. In contrast, the Y-Adam is estimated to have lived 20-50KYA. - this differene may reflect a difference in the variance in reproductive success of the sexes. - Y extinction more likely with promiscuity.
38
What is the vicious cycle that heterogamety generates?
Accumulation of sexually-antagonistic genes on X. 1. females have twice as many X chromosomes as males do - Female-benefit dominant alleles can become common, even if they cause harm to males. 2. Male X-linked genes are expressed in the hemizygous state - Male-benefit recessive alleles can become common, even when they cause harm in females.
39
What did Reeve and Pfennig find when they compared the number of display traits between different mating systems?
Related SD to the degree of heteromorphism of the sex chromosomes. - Highly heteromorphic ZW species had the highest degree of dimorphism - Authors suggested that something about the ZW system favored the evolution of secondary sexual traits. - Suggest that the pattern is due to SA genes. - Males transmit male-benefit Z genes to sons. - Females have more control of offspring sex
40
How does the genome cope with different numbers of X chromosomes in males (1) vs. females (2)?
Humans-inactivation (Lyonization) in females via the Barr body leads to a form of genetic mosaicism. -Drosophilia: doubling of X-expression in males.
41
What is the mechanism of inactivation?
Paternal X is imprinted and shut off early in embryogenesis during formation of the extraembryonic tissues (placenta) - Turned on again in early embryogenesis - Marsupials permanently shut off male X. One copy is then shut off, in each cell, in growth of embryo. - Condensed into heterochromatin for non-recombining region. - Produced potential for genetic mosaicism. - Recent recognition that there is a continuum between paternal X-inactivation and random inactivation
42
Why are X-linked disorders more common in men than women?
Women have a 'backup copy', expressed as a mosaic.
43
Is the other X chromosome really inactivated?
Recent research has shown that some Xi genes are expressed in the condensed heterochromatin state. - Inn addition to the PAR, as much as 25% of the Xi may actually have some gene expression. - Each female subject had a different Barr expression pattern.
44
What is the mechanism of imprinting for insulin-like growth factor?
Igf is imprinted by the mother. - Imprinted Igf gene expression strongly reduced. - Igf causes greater placental growth and greater nutrient flow: - more nutrition to foetus & cost to mother.
45
What is the Igf-r system?
It is a manose cell-surface receptor, which binds Igf competitively in the placenta and embryo. - Nothing to do with growth, directly. - ONLY female-inherited allele expressed (imprinted by male to shut off) - Igf-r system appears to be there to suppress excess Igf.
46
When would selection favour selfishness of the father and foetus? Who showed evidence of this?
The degree should depend upon the risk of polyandry. - Higher levels of sperm competition, or sequential polyandry, reduce relatedness between a male's offspring and others born of a female mate. The rule: extract nutrition NOW if mother is going to have kids via other fathers.....extract nutrition in any case! - Tristan Long showed evidence that in primates, placental morphology is correlated with risk of sperm competition and social system. - More developed and invasive placentae are associated with primates with higher Gonosomatic index or known polyandry.
47
What is the curve for benefit/cost ratio for fitness as offspring develop?
Babies need to nurse early on to survive (benefit high for the mother and baby both) -Energy needs are low when the baby is small, but nursing is essential. As baby grows, it becomes competent to accept other food. - Benefits to nursing decline, energy costs for mother increase - SElffish behavior of foetus/infant is greater when relatedness to other offspring is low; infant always wants more than the mother wants to give.
48
What is the conflict over how much to provision the offspring in male vs. female?
The conflict is over the inclusive fitness gains in male vs. female. -Inclusive fitness is the ability of an individual organism to pass on its genes to the next generation.
49
Why is the optimal benefit/cost ratio lower for offspring compared to mothers?
Offspring are only 50% related to mother; extract more resources than mother wants to give. They have a later optimal time for extracting resources.
50
How do females compensate for the energetic demands of breastfeeding?
They secrete benzodiazepines to soporific effect (induce sleep).
51
What is the Praeder-Willi syndrome?
Two copies of maternally-imprinted gene 15g11-13 = weak begging and sucking response. -Develop slowly. Adults are shorter, almost always infertile.
52
What is Angelman syndrome?
Two copies paternally imprinted = hyperactive but badly coordinated nursing.
53
Why might the optimal timing of weaning differ for male and female offspring?
In primates, son fitness depends on size/ability to achieve social dominance. - Males are nursed for longer than females in species with dominance hierarchies than in solitary primates. - If there is an opportunity to produce a dominant male through extended nursing, female may adjust her strategy plastically through postpartum provisioning.
54
What is the Trivers-Willard Hypothesis?
Females should nurse more sons when resources are abundant; daughters when resources are scarce.
55
What is the selection for imprinting in female plants?
When a different males'e pollen fertilizes a female's ovules, the paternal genome is selected to take as much nutrition as possible. - Selfish genes don't care about their rivals, even if female fitness is reduced. - The male is selected to make a bigger seed. SELECTs for females to imprint ovule/seed growth genes.
56
What is the imprinting selection when a plant self-fertilizes?
When a plant self-fertilizes, all ovules have the same father. - Reproductive interests of males and females are the same. - No selection for imprinting by the female.
57
What is the effect of paternal imprinting on the brain?
Increased and/or dysregulated brain growth; more self-oriented behavior, less mentalistic. Autism - Higher levels of brain growth factors. -Upregulated PI3K pathway.
58
What is the effect of maternal imprinting on the brain?
Reduced or dysregulated brain growth; hyper-mentalistic behavior. Psychosis - Lower levels of brain growth factors -Downregulated PI3K pathway.
59
Where will the parent-offspring conflict be absent? | 1
When there is a high relatedness of parents - In plants, seeds are provisioned after fertilization. - If there are many pollen-donors, i.e. outbreeding, the males compete for the female's energy investment. - If the plant selfs, then there is no conflict between ovules. -In Arabidopsis and its relatives, selfing species do produce smaller seeds.
60
Where will the parent-offspring conflict be absent? | 2
When there is genetic monogamy the interests of the parents are identical. BUT offspring are still only 0.5 related! -Still not in harmony with parents.

Biology 369 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions