p.1
Gonad Development and SRY Gene
How do eggs and sperm differentiate?
Gonads instruct differentiation of germ cells into eggs and sperm.
p.2
Meiosis and Gametogenesis
What happens during improper segregation in meiosis?
It can lead to conditions like XXY (male) or XO (female).
p.5
Environmental Influences on Sex Determination
Which gene's expression correlates with sex determination in the red-eared slider turtle?
Histone demethylase KDM6B.
p.6
Primordial Germ Cells and Differentiation
Where do primordial germ cells (PCGs) form?
In the posterior epiblast.
p.7
Meiosis and Gametogenesis
What occurs before the first meiotic division?
DNA replication, resulting in chromosomes composed of two identical chromatids.
p.7
Meiosis and Gametogenesis
What happens during Metaphase I of meiosis?
Paired homologous chromosomes undergo crossing over and recombination and align on the meiotic spindle.
p.6
Gonad Development and SRY Gene
What instructs the differentiation of primordial germ cells into eggs and sperm?
Cell-cell signaling in the gonads.
p.4
Sex Determination in Drosophila
What is a 'Gynandromorph' in Drosophila?
A female/male genetic mosaic.
p.4
Sex Determination in Drosophila
What happens when one X chromosome is lost from an embryonic nucleus in Drosophila?
All resultant daughter cells are XO (male).
What does the sperm bind to after penetrating the cumulus layer?
The zona pellucida, a thick matrix of glycoproteins.
p.7
Meiosis and Gametogenesis
How does meiosis contribute to genetic diversity?
By generating genetic diversity via recombination.
p.4
Sex Determination in Drosophila
What does Sxl activity lead to in terms of RNA splicing?
It causes sex-specific splicing of dsx RNA, leading to female development (dsx f).
p.9
Meiosis and Gametogenesis
What has been completed in the egg by the time the sperm nucleus enters?
Meiosis, resulting in the formation of a female pronucleus.
p.8
Oogenesis and Spermatogenesis
What happens to the number of oocytes as a female ages?
It declines, as oocytes do not proliferate after entering meiosis.
p.3
Gonad Development and SRY Gene
What is the role of Sertoli cells?
Essential for testis formation and sperm generation.
p.3
Gonad Development and SRY Gene
What is the function of Sox9 in testis differentiation?
It promotes testis differentiation and upregulates Fgf9 while repressing Wnt4.
p.1
Chromosomal Sex Determination
How do chromosomes determine sex?
X- and Y-linked genes determine gonad development.
p.1
Environmental Influences on Sex Determination
What influences sex determination besides chromosomes?
Environmental influences.
p.2
Chromosomal Sex Determination
How is sex determined in mammals?
By the presence of either a second X chromosome or a Y chromosome.
p.12
Fertilization Process
What event does sperm-egg fusion induce during fertilization?
A calcium wave that activates the egg.
p.12
Fertilization Process
How is calcium concentration monitored during fertilization?
Using fluorescent dye and confocal microscopy.
p.12
Fertilization Process
What role does Phospholipase C (PLC) play in egg activation?
It cleaves PIP2 to generate IP3 and diacylglycerol (DAG).
p.5
Environmental Influences on Sex Determination
What type of sex determination occurs in reptiles?
Temperature-dependent sex determination.
p.12
Fertilization Process
What does IP3 do in the process of egg activation?
It binds to a receptor and releases calcium from the endoplasmic reticulum (ER).
p.2
Gonad Development and SRY Gene
What does the presence of a Y chromosome indicate?
It typically indicates male gonad development.
p.12
Fertilization Process
What is the significance of the calcium wave in fertilization?
It activates the egg and initiates metabolic reactions for embryonic development.
p.5
Environmental Influences on Sex Determination
What is required for both males and females to hatch from the same brood of eggs?
A small range of temperatures.
p.2
Gonad Development and SRY Gene
What does the absence of a second X chromosome indicate?
It can lead to a female phenotype (XO).
p.5
Environmental Influences on Sex Determination
What type of temperatures lead to the activation of Kdm6b during gonad specification?
Male-producing temperatures.
p.6
Primordial Germ Cells and Differentiation
What do gametes differentiate from during development?
Primordial germ cells (PCGs).
p.5
Environmental Influences on Sex Determination
What is unknown regarding the sex determination process in reptiles?
The activators and target genes.
p.7
Meiosis and Gametogenesis
What is the primary purpose of meiosis?
To reduce the chromosome number from diploid (2n) to haploid (n).
p.6
Primordial Germ Cells and Differentiation
What do BMPs do once primordial germ cells reach the gonad?
They maintain PCGs by activating germ line-specific genes and suppressing genes that prevent germ line specification.
p.6
Meiosis and Gametogenesis
What role does the Stra8 transcription factor play in germ cells?
It promotes DNA synthesis and initiates meiosis.
p.10
Acrosomal Reaction in Sperm
What is the purpose of the acrosomal reaction?
To help sperm penetrate the zona pellucida and fuse with the egg membrane.
p.6
Primordial Germ Cells and Differentiation
How do primordial germ cells migrate to the gonads?
They migrate through the gut and then dorsally into the genital ridges.
What initiates development in mammals?
Fertilization, involving the fusion of egg and sperm.
p.10
Acrosomal Reaction in Sperm
What happens during the acrosomal reaction in sea urchin sperm?
Sperm release contents of acrosomes by exocytosis.
p.7
Meiosis and Gametogenesis
What occurs during the first meiotic division?
Homologous chromosomes separate and are segregated into different daughter cells.
p.11
Polyspermy Prevention Mechanisms
What happens to the embryo if polyspermy occurs?
The embryo dies due to fusion of multiple haploid nuclei.
p.11
Polyspermy Prevention Mechanisms
What is the result of fusion of three haploid nuclei?
It results in 54 chromosomes that randomly assort on four spindles.
p.11
Polyspermy Prevention Mechanisms
What is the fast block to polyspermy?
Depolarization of the egg cell membrane within 3 seconds.
What is the acrosomal reaction?
The release of digestive enzymes from the sperm head to break down the zona pellucida.
p.10
Acrosomal Reaction in Sperm
What role does Izumo play in mouse fertilization?
Izumo localizes to the sperm cell membrane and binds to a complex of Juno and other egg membrane proteins, initiating membrane fusion.
p.9
Polyspermy Prevention Mechanisms
What occurs when the sperm and egg plasma membranes fuse?
Cortical granules are released from the egg to block polyspermy.
What enters the egg cytoplasm after fertilization?
The sperm nucleus and its contents.
p.11
Polyspermy Prevention Mechanisms
What happens to the egg cell membrane after depolarization?
Sperm cannot fuse with egg cell membranes that have a positive resting potential.
p.8
Oogenesis and Spermatogenesis
When do spermatocytes undergo meiosis?
After birth, continuing throughout life.
p.3
Gonad Development and SRY Gene
What does Wnt4 promote?
Ovary differentiation by repressing Sox9.
p.4
Sex Determination in Drosophila
How is sex determined in Drosophila?
By the number of X chromosomes.
p.7
Meiosis and Gametogenesis
Is there DNA replication before the second meiotic division?
No, there is NO DNA REPLICATION before the second meiotic division.
p.10
Acrosomal Reaction in Sperm
What facilitates adhesion to the egg plasma membrane during the acrosomal reaction?
The extension of the rod-like acrosome process formed by actin polymerization.
p.4
Sex Determination in Drosophila
What is the role of the Sex-lethal (Sxl) gene in Drosophila?
It is an X-linked transcription factor required for female development.
p.11
Polyspermy Prevention Mechanisms
How does the fast block to polyspermy occur?
Binding of the first sperm opens Na+ ion channels, causing Na+ influx and depolarization.
What happens after the sperm penetrates the zona pellucida?
It binds to the egg plasma membrane.
p.10
Acrosomal Reaction in Sperm
What happens if there are loss-of-function mutations in Izumo or Juno?
They block fertilization.
p.3
Gonad Development and SRY Gene
What is the primary sex-determining gene in mammals?
The SRY gene on the Y chromosome.
p.3
Gonad Development and SRY Gene
What can happen during meiosis that affects sex determination?
Crossing over can transfer the SRY gene to the X chromosome, resulting in XX males.
p.11
Polyspermy Prevention Mechanisms
What is polyspermy?
The condition when multiple sperm enter an egg.
p.10
Acrosomal Reaction in Sperm
What do acrosome enzymes do during the acrosomal reaction?
They break down the oligosaccharide side chains on the zona pellucida glycoproteins, clearing a path to the egg plasma membrane.
What is the cumulus layer?
A sticky layer of hyaluronic acid secreted by follicle cells.
p.7
Meiosis and Gametogenesis
What happens during the second meiotic division?
Daughter chromatids separate and segregate into different daughter cells.
p.10
Acrosomal Reaction in Sperm
What proteins are exposed on the sperm surface during the acrosomal reaction?
Proteins that bind to the egg membrane and allow fusion.
p.11
Polyspermy Prevention Mechanisms
What is the slow block to polyspermy?
The cortical granule reaction that occurs within 15 to 60 seconds.
p.4
Sex Determination in Drosophila
What occurs in the absence of Sxl in Drosophila?
Splicing of dsx RNA leads to male development (dsx m).
p.8
Oogenesis and Spermatogenesis
What happens to primary oocytes during embryonic development?
They enter meiosis but are arrested in Prophase I.
p.11
Polyspermy Prevention Mechanisms
What does the tough fertilization membrane do?
It prevents further sperm entry after fertilization.
p.8
Oogenesis and Spermatogenesis
How does maternal age affect trisomies?
Trisomies increase with maternal age.
p.8
Oogenesis and Spermatogenesis
What happens to germ cells during embryonic development in spermatogenesis?
They are arrested in G1 and do not enter meiosis.
