Lec 5. Sex determination and sex linked characteristics Flashcards
What gene determines sex?
SRY gene
What protein determines sex?
TDF
How many pairs of chromosomes do platypus’s have?
5 pairs. 5 Xs 5Ys or 10Xs
What is heteromorphic?
X and Y are called heteromorphic
What is the primary testis initiation gene in therian mammals?
SRY
Define sexual reproduction
Alternates between haploid and diploid states
What does Fertilization produce?
a diploid zygote
What does Meiosis produce?
Haploid gametes
Define heterogametic
sex produces 2 different gamete types -with 2 different sex chromosomes
True or False? Most organisms have two sexual phenotypes, male and female.
True
Define Parthenogenesis
reproduction without males
In mammals, the X and Y chromosomes usually do what during meiosis?
pair even though they are not homologous
How many genes are on the Y chromosome?
around 30
How many genes are on the X chromosome?
more than the Y a lot.
What are autosomes?
Non-sex chromosomes.
What are the sex chromosomes for insects?
XX (f)-XO (m)
What are the sex chromosomes for birds and reptiles?
ZW (f) -ZZ (m)
What is the role of the X sex chromosome?
contains genetic info essential for both sexes. At least one copy of an X is required
What is the role of the Y chromosome?
male-determining gene is located here.
Where are the X and Y chromosomes only homologous in?
pseudoautosomal regions
In the Haplodiploidy system: Haploid set is
Male (unfertilized)
In the Haplodiploidy system: Diploid set is
Female (union of sperm and egg)
What is the genic sex-determining system and where is it found?
No sex chromosomes, only sex-determining genes. Found in plants, fungi, fish.
What is an example of environmental sex determination?
aquatic snail, limpets position in stack determines sex
What is another example of environmental sex determination?
Alligators temperature-dependent sex determination
what is the genotype for Turner syndrome?
XO. Females
What is the genotype for Klinefelter syndrome?
XXY, XXXY or XXXXY or XXYY. Males
What are the signs and symptoms of a person with Turner Syndrome?
Short, high arched palate, retrognathia, webbed neck, droopy eyes, lazy eye, broad chest
What are the signs and symptoms of Klinefelter syndrome?
After 5 years of age, boys are taller and fatter around belly, clumsy, slow motor skills.
In what way could the SRY gene not function?
Androgen-insensitivity syndrome
What happens if the SRY gene gets translocated onto the X?
XX, male phenotype with testicular disorder of sex development.
