Reproduction importance Flashcards
(19 cards)
What 3 mechanisms in meiosis lead to genetic diversity
Independent chromosome assortment
Crossing over
Random fertilisation
Sexual reproduction
process of bringing together two haploid gametes (one from each parent) to form a diploid zygote
Weinsmann’s hypothesis
Sex increases genetic diversity, which improves a population’s ability to adapt to changing environments.
Muller ratches hypothesis
in asexual reproduction, harmful mutations can accumulate over generations
Sex helps by recombining genes, which can eliminate those bad mutations, keeping the genome “cleaner.”
Fisher hypothesis
Sex allows beneficial mutations from different individuals to combine in one offspring.
Red queens hypothesis
generates variation to battle parasitic load
Tangled bank hypothesis
The Tangled Bank Hypothesis says sexual reproduction is useful because:
It creates variety in offspring.
That variety means less competition between siblings.
It increases the chance that at least some offspring will do well in a changing or crowded environment.
Chromosomes in males and females
Males - XY
Females - XX
Kleinfelters syndrome
when males have XXY syndrome
Turner’s syndrome
when females have XO chromosome
What is SDR and where is it found?
decides whether the baby is male or female
found on Y chromosome in males
How long is SRY active for
few hours during gonad development
Loss or inactivation of SRY gene
Normally, males are XY and have the SRY gene on their Y chromosome, which drives male development.
But if the SRY gene is lost or doesn’t work (e.g., due to mutation or inactivation), the development path fails to trigger male traits.
Despite having XY chromosomes, the embryo will develop female characteristics because there’s no SRY to trigger the male development.
So, in this case, you get an XY female — someone who is genetically male (XY) but develops female features because the SRY gene is inactive or missing.
SRY transfers to X chromosome
In some rare cases, the SRY gene can move from the Y chromosome to an X chromosome during genetic recombination (a process that can happen when sperm cells are being made).
If a person ends up with two X chromosomes (XX), but one of those X chromosomes carries the SRY gene, then the person will develop male traits even though they are genetically XX.
This is why the person is called an XX male — they are genetically female (XX), but have male characteristics because of the SRY gene
What does sex-dermining gene produce
testis determining factor
TDF triggers the development of testes in the embryo, starting the process of male sex differentiation.
Before differentiating into males or females, what happens
Germ cells migrate to yolk sac.
Wofflian ducts and mullerian ducts begin development.
Urogenital sinus and tubercule develop
mullerian ducts are precursors to
female reproductive system
Wollfian ducts are precursors to
male reproductive system
Sox 9
SOX9 is a critical gene involved in the development of the male sex determination pathway.
SOX9 is essential for the formation of testes in males.
In XY (male) embryos, the SRY gene (Sex-determining Region of the Y chromosome) gets activated, which in turn activates SOX9.
SOX9 then triggers the development of testes by influencing the expression of other genes required for testicular formation.
