Lecture 9 - How Can DNA From Two Parents Combine to Form One Offspring? Flashcards
briefly explain the process of meiosis
- chromosomes duplicate
- homologs separate
- sister chromatids separate
Briefly explain the process of mitosis
- chromosomes duplicate
- sister chromatids separate
what are somatic cells?
all cells in the bod apart from gametes and their precursors
Explain pairs of homologous chromosomes in the zygote
one from mother one from father
Explain the process of crossing over
- homologous chromosomes find each other
- DNA breaks are induced
- synaptonemal complex assembly begins
- crossing over occurs
- synaptonemal complex assembly completed
- chiasmata visible
- synaptonemal complex disassembles
When does crossing over happen?
during meiosis
- prophase I
what is the synaptonemal complex?
protein structure that forms between homologous chromosomes
what are the 3 types of variation within meiosis?
1) crossing over
2) independent assortment
3) random fertilisation
Explain the process of meiosis I
- chiasmata is holding chromosomes together
- kinetochores attach o microtubules at the same pole
- cohesin holds sister chromatids together
- seperase cleaves cohesin on chromosome arms but cohesin is protected at centromeres
- homologous chromosomes are now separated
- sister kinetochores attach to microtubules from opposite poles
- cohesin is cleaved at centromeres
- sister chromatids go to opposite poles
What are recombinant chromosomes?
chromosomes that have undergone crossing over
What are chromosomes that remain the same in meiosis called?
parental chromosomes
Explain the process of independent assortment
chromosomes align in either direction on the meiosis I and II spindle
Explain random fertilisation
any sperm can fertilise any egg
