Unit 11: Sex Chromosomes and Inheritance Flashcards
X and Y are considered homologous sex chromosomes but do not…
cross over
What is the SRY gene?
Found on the Y chromosome and initiates male sex determination by stimulating the development of testes and testosterone.
What develops if a zygotes is XX and therefore has no SRY gene?
Develops ovaries and estrogen progesterone.
What is gonadal sex?
Refers to whether an individual develops testes (male gonads) or ovaries (female gonads).
What is chromosomal sex?
Refers to the sex chromosomes (XX or XY) present in an individual’s cells, determined at fertilization.
What is XY-?
Refers to an individual with an XY chromosomal makeup but with a missing or nonfunctional Y chromosome.
What is the phenotype of someone who has XY- chromosome?
They develop female external genitalia despite having XY chromosomes.
What are three models of the Human Y?
- Dominant Y
- Selfish Y
- Wimp Y
What is dominant Y?
Was considered dominant Y because it contains male determining gene.
What is Selfish Y?
Y kidnapped genes from
elsewhere.
What is wimp Y?
Y is just a relic of an X.
Why is the Y chromosome disappearing out of the human genotype?
Y is small, gene poor, and prone to deletion and loss, and somewhat useless. You can lack a Y and be perfectly healthy.
When does the SRY gene express itself?
At around 6 weeks post-fertilization, the SRY gene expresses in XY individuals forming testes and male structures.
