It's all about sex Flashcards
(25 cards)
What separates during Meiosis I?
Homologous chromosomes
What separates during Meiosis II?
Sister chromatids
What is the end result of meiosis?
Four genetically unique haploid gametes
Why is cytoplasmic division unequal in females during meiosis?
To retain most cytoplasm in one oocyte; other products become polar bodies
What is restored at fertilisation?
The diploid chromosome number
How did meiosis likely evolve?
From mitosis in early eukaryotes
What is nondisjunction?
Failure of chromosomes to separate properly, causing extra or missing chromosomes
What condition is caused by trisomy 21?
Down syndrome
Why are sex chromosome aneuploidies often less severe?
Because of X inactivation and limited Y chromosome genes
What are three forms of horizontal gene transfer in prokaryotes?
Conjugation, transformation, and transduction
What is a key advantage of sexual reproduction?
It increases genetic diversity through recombination and fertilisation
What are some disadvantages of sexual reproduction?
Requires two individuals, breaks up adaptive gene combinations, and has reproductive costs
What is a meiotic driver?
A selfish gene variant that biases inheritance in its favour
What is anisogamy?
A condition where gametes differ in size (e.g., sperm and eggs)
What is isogamy?
Gametes of equal size, seen in some unicellular organisms
What is parthenogenesis?
Asexual reproduction where females produce offspring from unfertilised eggs
What supports the idea that sexual reproduction reduces extinction risk?
Asexual lineages are often short-lived
What is the heterogametic sex in humans?
Males (XY)
What is haplodiploidy?
A system where males are haploid and females are diploid, e.g., in bees
Give an example of environmental sex determination
Temperature-dependent sex in turtles and alligators
What sex chromosomes do birds have?
Females are ZW, males are ZZ
Why are X-linked recessive disorders more common in males?
Males only have one X chromosome, so one recessive allele causes the condition
What is an example of an X-linked trait?
Red-green colour blindness
How is mitochondrial DNA inherited?
From the mother through the egg’s cytoplasm
