Meiosis + Genetic Variation 2 Flashcards
What is independent segregation?
The random arrangement and separation of homologous chromosomes pairs during meiosis I
When does independent segregation occur?
During meiosis I, when homologous chromosomes line up in pairs
Why does independent segregation lead to genetic variation?
This is because the combination of maternal and paternal chromosomes in each daughter cell is random and due to chance
What determines which chromosomes from each pair end up in a daughter cell?
The random orientation of each homologous pair during alignment in meiosis I
How is independent segregation different from crossing over?
Independent segregation involves the random assortment of whole chromosomes, while crossing over involves the exchange of genetic material between chromatids
What is responsible for creating new genetic combinations during meiosis?
The independent assortment of homologous chromosomes, which randomly distributes maternal and paternal alleles into gametes
Give an example of two characteristics that can vary due to different alleles on homologous chromosomes? (tongues + blood)
Tongue rolling (being able to roll vs. not being able to roll tongue)
Blood group (blood group type A vs. blood group type B)
At which stage of meiosis do homologous chromosomes segregate (separate) into separate cells?
At the end of meiosis I
At which stage of meiosis do chromatids separate to form four gametes?
At the end of meiosis II
When does crossing over occur during meiosis?
During meiosis I, when homologous chromosomes line up alongside each other
What physically happens to chromatids during crossing over?
Chromatids of homologous chromosomes twist around each other, creating tension that may cause portions to break off
What happens to the broken portions of chromatids during crossing over?
They rejoin with the chromatids of the homologous partner, usually exchanging equivalent portions
What is the result of recombination by crossing over?
New genetic combinations of maternal and paternal alleles are produced
How does crossing over affect the variety of cells produced at the end of meiosis?
Without crossing over, only two types of cells are produced. With crossing over, up to four genetically different cells can be formed
Why are gametes produced by meiosis, genetically different?
This is because they contain different combinations of maternal and paternal chromosomes and alleles due to independent assortment and crossing over
What is the chromosomes number in gametes produced by meiosis?
Haploid (half the number of chromosomes of the parent cell)
How does random fusion of gametes at fertilisation contribute to genetic variation?
Each gamete has a different genetic makeup so their radnom fusion creates new combinations of alleles in the offspring
How is genetic variety further increased when gametes come from different parents?
Two different genetic makeups are combined, leading to even more variation in the offspring
What are the two main sources of genetic variation during sexual reproduction?
- The independent assortment and crossing over during meiosis
- The random fusion of genetically different gametes at fertilisation
