WEEK 7 Flashcards
(23 cards)
What are the learning objectives of Week 7?
Understand somatic vs germline cells, meiosis, and how genetic variation arises. (Slide 3)
What does diploid (2n) mean in eukaryotes?
Having two sets of chromosomes, one from each parent. (Slide 4)
What are homologous chromosomes?
Pairs of chromosomes containing the same genes, one from each parent. (Slide 4)
What is a haploid (1n) cell?
A cell with one complete set of chromosomes, such as a gamete. (Slide 4)
What does meiosis produce?
Haploid gametes (sperm and egg). (Slide 5, Slide 10)
What happens during fertilization?
Two haploid gametes fuse to form a diploid zygote. (Slide 5)
What is the alternation of generations in ferns?
A life cycle involving multicellular diploid and haploid stages. (Slide 6)
What are gametophytes in plants?
Haploid organisms that produce gametes by mitosis. (Slide 6)
Where does meiosis occur in flowering plants?
In microsporangia and megasporangia of anthers and ovaries. (Slide 7)
What are micro- and mega-gametophytes?
Pollen grain and embryo sac, structures producing sperm and egg. (Slide 7)
What does meiosis involve?
One round of DNA replication and two cell divisions. (Slide 10)
What happens in Meiosis I?
Homologous chromosomes separate, reducing chromosome number to haploid. (Slide 11)
What happens in Meiosis II?
Sister chromatids separate, similar to mitosis. (Slide 11)
How does independent assortment create variation?
Different combinations of chromosomes segregate into gametes. (Slide 13)
How many unique gametes can a human produce?
About 8 million (2^23) due to independent assortment. (Slide 13)
What is crossing over?
Exchange of genetic material between nonsister chromatids in meiosis I. (Slide 13)
When does crossing over occur?
During pachytene of Prophase I in meiosis I. (Slide 13)
What are recombination hotspots?
Sites on chromosomes where crossing over occurs more frequently. (Slide 13)
How many crossovers occur on average per chromosome pair?
About 2–3. (Slide 14)
What does crossing over result in?
New combinations of alleles, increasing genetic diversity. (Slide 14)
What four mechanisms contribute to genetic variation?
Mutation, independent assortment, recombination, and gamete fusion. (Slide 16)
What is nondisjunction?
Failure of chromosomes or chromatids to separate during meiosis. (Slide 17)
What can result from nondisjunction?
Aneuploidy, such as trisomy 21 (Down syndrome). (Slide 17)
