Podcast
Questions and Answers
What term is used to describe organisms that contain both male and female reproductive organs?
What term is used to describe organisms that contain both male and female reproductive organs?
Which type of gametes do Chlamydomonas produce that are morphologically indistinguishable?
Which type of gametes do Chlamydomonas produce that are morphologically indistinguishable?
In Chlamydomonas, what type of cells can mt– cells mate with?
In Chlamydomonas, what type of cells can mt– cells mate with?
What is the main reproductive structure present in a monoecious plant like maize?
What is the main reproductive structure present in a monoecious plant like maize?
Signup and view all the answers
What does the term 'intersex' refer to in the context of sexual differentiation?
What does the term 'intersex' refer to in the context of sexual differentiation?
Signup and view all the answers
Which of the following best describes the life cycle of Chlamydomonas during unfavorable nutrient conditions?
Which of the following best describes the life cycle of Chlamydomonas during unfavorable nutrient conditions?
Signup and view all the answers
What process links the diploid sporophyte stage and the haploid gametophyte stage in plants?
What process links the diploid sporophyte stage and the haploid gametophyte stage in plants?
Signup and view all the answers
What type of organisms are described as being unisexual?
What type of organisms are described as being unisexual?
Signup and view all the answers
What determines maleness in humans?
What determines maleness in humans?
Signup and view all the answers
Which syndrome is characterized by having a 47,XXY karyotype?
Which syndrome is characterized by having a 47,XXY karyotype?
Signup and view all the answers
What physical characteristic is commonly associated with Turner syndrome?
What physical characteristic is commonly associated with Turner syndrome?
Signup and view all the answers
Individuals with Klinefelter syndrome typically experience which of the following?
Individuals with Klinefelter syndrome typically experience which of the following?
Signup and view all the answers
What is a common feature of individuals with 47,XXX syndrome?
What is a common feature of individuals with 47,XXX syndrome?
Signup and view all the answers
Which of the following is NOT a symptom of Klinefelter syndrome?
Which of the following is NOT a symptom of Klinefelter syndrome?
Signup and view all the answers
What genetic abnormality is often seen in individuals with 47,XYY?
What genetic abnormality is often seen in individuals with 47,XYY?
Signup and view all the answers
Which condition results from the presence of only one X chromosome in females?
Which condition results from the presence of only one X chromosome in females?
Signup and view all the answers
What term describes the highly condensed inactive X chromosome in females?
What term describes the highly condensed inactive X chromosome in females?
Signup and view all the answers
According to the Lyon hypothesis, what is true about X-inactivation?
According to the Lyon hypothesis, what is true about X-inactivation?
Signup and view all the answers
What is the condition called in females where a mutated gene on the active X chromosome affects sweat gland formation?
What is the condition called in females where a mutated gene on the active X chromosome affects sweat gland formation?
Signup and view all the answers
What is one possible effect of Triple X Syndrome in females?
What is one possible effect of Triple X Syndrome in females?
Signup and view all the answers
What is the primary function of dosage compensation in mammals?
What is the primary function of dosage compensation in mammals?
Signup and view all the answers
Which gene is most influential in the X-inactivation center (Xic)?
Which gene is most influential in the X-inactivation center (Xic)?
Signup and view all the answers
Which region is critical for the segregation of X and Y chromosomes during male gametogenesis?
Which region is critical for the segregation of X and Y chromosomes during male gametogenesis?
Signup and view all the answers
In Drosophila, what determines the sex of the organism?
In Drosophila, what determines the sex of the organism?
Signup and view all the answers
Which of the following is NOT a characteristic often associated with XYY males?
Which of the following is NOT a characteristic often associated with XYY males?
Signup and view all the answers
What is the process whereby gene expression from one homologous chromosome is affected while the other remains unaffected called?
What is the process whereby gene expression from one homologous chromosome is affected while the other remains unaffected called?
Signup and view all the answers
What is the overall trend in the male to female birth ratio worldwide?
What is the overall trend in the male to female birth ratio worldwide?
Signup and view all the answers
What does the presence of the SRY gene influence in humans?
What does the presence of the SRY gene influence in humans?
Signup and view all the answers
What characterizes XO flies in Drosophila?
What characterizes XO flies in Drosophila?
Signup and view all the answers
Why might there be more male spontaneous abortions compared to females?
Why might there be more male spontaneous abortions compared to females?
Signup and view all the answers
What is suggested by the primary sex ratio in human conception?
What is suggested by the primary sex ratio in human conception?
Signup and view all the answers
What factor contributes to the actual number of boys born being greater than the expected 1:1 ratio?
What factor contributes to the actual number of boys born being greater than the expected 1:1 ratio?
Signup and view all the answers
What does the X:A ratio of 1.0 indicate for female Drosophila?
What does the X:A ratio of 1.0 indicate for female Drosophila?
Signup and view all the answers
What is the result of an X:A ratio of 3X:2A in female Drosophila?
What is the result of an X:A ratio of 3X:2A in female Drosophila?
Signup and view all the answers
How does temperature influence sex determination in reptiles?
How does temperature influence sex determination in reptiles?
Signup and view all the answers
Which statement is true regarding XO males in Drosophila?
Which statement is true regarding XO males in Drosophila?
Signup and view all the answers
What happens to the sex determination of the Australian lizard Eulamprus tympanum due to global warming?
What happens to the sex determination of the Australian lizard Eulamprus tympanum due to global warming?
Signup and view all the answers
Which of the following describes intersex Drosophila?
Which of the following describes intersex Drosophila?
Signup and view all the answers
What role do polychlorinated biphenyls (PCBs) play in reptilian sex determination?
What role do polychlorinated biphenyls (PCBs) play in reptilian sex determination?
Signup and view all the answers
Which of the following ratios indicates a male Drosophila?
Which of the following ratios indicates a male Drosophila?
Signup and view all the answers
Study Notes
Life Cycles and Sexual Differentiation
- Multicellular organisms differentiate between primary sexual differentiation (gonad development) and secondary sexual differentiation (external appearance).
- Unisexual (dioecious or gonochoric) organisms have either male or female reproductive organs.
- Bisexual (monoecious or hermaphroditic) organisms contain both male and female reproductive organs.
- Intersex individuals have intermediate sexual differentiation, often resulting in sterility.
- Chlamydomonas is an example of an organism that spends most of its life cycle in the haploid phase. However, under unfavorable conditions, certain daughter cells become gametes that fuse during mating, producing a diploid zygote.
- Chlamydomonas haploid gametes are of two mating types, mt– and mt+.
- Chlamydomonas gametes are isogametes, meaning they are not morphologically distinguishable.
- Isogamy refers to species producing morphologically similar gametes.
- In many plants, there is an alternation between the diploid sporophyte stage and the haploid gametophyte stage.
- The sporophyte stage predominates in maize (Zea mays), a monoecious plant.
Sex Determination and the Y Chromosome
- Klinefelter syndrome (XXY) results in male offspring, while Turner syndrome (X) results in female offspring, indicating that the Y chromosome determines maleness.
- The Y chromosome is smaller than the X chromosome and contains fewer genes.
- The pseudoautosomal regions (PARs) on the Y chromosome share homology with regions on the X chromosome and are essential for proper chromosome segregation during meiosis.
- The male-specific region of the Y (MSY) contains the sex-determining region of the Y (SRY).
- The testis-determining factor (TDF), encoded by a gene in the SRY, triggers testes formation.
- The MSY further consists of three regions: the X-transposed region, the X-degenerative region, and the ampliconic region.
The Ratio of Males to Females
- The primary sex ratio is the proportion of males to females conceived in a population.
- The secondary sex ratio is the proportion of each sex born.
- Secondary sex ratios are greater than 1.0 in several populations, suggesting that more males are born than females.
- This is attributed to the fact that the Y chromosome is lighter than the X chromosome, leading to a higher rate of male fertilization.
- However, more male fetuses are spontaneously aborted during gestation, contributing to the observed sex ratio at birth.
Dosage Compensation
- Dosage compensation balances the expression of X-linked genes in females and males.
- In females, one X chromosome becomes inactive and is condensed into a Barr body.
- The Lyon hypothesis states that X-inactivation occurs randomly in somatic cells.
- Anhidrotic ectodermal dysplasia is an example of X-linked gene inactivation in females where the active X chromosome carries a mutation causing sweat gland defects.
X-Inactivation
- Imprinting involves selective gene expression from one chromosome homolog over the other.
- The X-inactivation center (Xic) on the inactive X chromosome plays a crucial role in inactivation.
- The X-inactive specific transcript (XIST) gene in the Xic is essential for silencing most genes on the inactive X chromosome.
Sex Determination in Drosophila
- Sex determination in Drosophila is based on the ratio of X chromosomes to haploid sets of autosomes (X:A ratio).
- A normal female (2X:2A) has an X:A ratio of 1.0.
- Triploid females (3X:3A) are fertile while sterile females (3X:2A) have an X:A ratio of 1.5.
- Normal male (XY:2A) and sterile male (XO:2A) flies have an X:A ratio of 0.5.
- Flies with an X:A ratio between 0.5 and 1.0 exhibit intersex morphology and sterility.
- The genic balance theory explains the threshold for maleness and femaleness based on the X:A ratio.
Temperature-Dependent Sex Determination in Reptiles
- Some reptiles, like crocodiles, turtles, and certain lizards, have temperature-dependent sex determination (TSD).
- This means that the incubation temperature of eggs during a critical period of embryonic development determines the sex of the offspring.
- Aromatase, an enzyme that converts androgens to estrogens, plays a critical role in TSD.
- TSD patterns vary across species, with different temperature ranges resulting in male or female offspring.
- Global warming may disrupt TSD in some reptile species, potentially leading to skewed sex ratios.
Sex Determination and Pollutants
- Pollutants such as polychlorinated biphenyls (PCBs) can disrupt sex determination in TSD organisms.
- PCBs can mimic estrogens, leading to female development even when eggs are incubated at temperatures that normally favor male development.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the complexities of sexual differentiation in multicellular organisms through this quiz. Understand the distinctions between unisexual and bisexual organisms, and the role of Chlamydomonas in haploid and diploid phases. Test your knowledge on concepts such as intersex and isogamy.
