Chromosome Inheritance Session 19

Question 1

What is the final result of Meiosis ?

Answer 1

• It results on four daughter cells with each of them having 23 chromosome pairs , and they are also haploid (n).
• Each of the daughter cells is genetically different from the parent cell

Question 2

When the chromosomes are paired in the diploid parent cell , what are the members of a pair called?

Answer 2

• Homologous chromosomes or Homologues

Question 3

What occurs during synapsis?

Answer 3

• Its when. homologous chromosomes come together and line up , side by side on the metaphase plate during meiosis I.
• Then chromosomal crossover occurs between them.

Question 4

What are the 5 stages of Meiotic Prophase I?

Answer 4

1. Leptotene
   - Chromosomes become individualized to form visible strands within the nucleus, recombination is initiated in this stage by the enzyme SPO11 which creates programmed double strand breaks
2. Zygotene
   - Telomeres cluster at one end of the nucleus, and synapsis begins. synapsis occurs in a zipper like fashion
3. Pachytene
   - all autosomal chromosomes have now synapsed and crossing over is complete and repair of the double strand breaks formed in leptotene is complete
4. Diplotene
   - Synpatonemal complex starts to disappear and chiasma are visible
5. Diakinesis
   - Chromosomes condense further . allowing for the first time to see the four parts of the tetrads. Sites of crossing over entangle together , effectively overlapping , making chiasmata clearly visible

Question 5

What occurs during Metaphase I?

Answer 5

• the homologous pairs align independently at the equator.

Question 6

What occurs during Meiosis II ?

Answer 6

• The sister chromatids separate and move toward opposite poles of the spindle
• The daughter cells mature into gametes and you end with 4 daughter cells which are all haploid

Question 7

How does meiosis help with genetic variation?

Answer 7

• Meiosis ensures that offspring will be diploid and have a combination of genetic characteristics different from that of a either parent

Question 8

What is the significance of Meiosis ?

Answer 8

• to keep chromosome number constant from generation to generation
• genetic recombination

Question 9

When and how many times does DNA replication take place in both meiosis and mitosis ?

Answer 9

• It happens only once and it happens prior to meiosis and mitosis

Question 10

How many nuclear divisions occur in meiosis and mitosis

Answer 10

• Two in meiosis
• Once in mitosisH

Question 11

How many daughter cells do mitosis and meiosis produce ?

Answer 11

• Meiosis produces four
• mitosis produces two

Question 12

Are the daughter cells of mitosis and meiosis haploid (n) or diploid (2n)?

Answer 12

• Meiosis are Haploid
• Mitosis are Diploid

Question 13

After meiosis and mitosis , are the daughter cells genetically identical or not ?

Answer 13

• For meiosis they are not genetically identical
• For mitosis they are genetically identical

Question 14

How can the specific differences between the nuclear divisions of mitosis and meiosis be categorized ?

Answer 14

• According to Occurrence and Process

Question 15

How often does meiosis and mitosis occur ?

Answer 15

• Meiosis occurs only in the reproductive organs and produces the gametes, millions of meiosis in males , only 400 in females.
• Mitosis is much more common , it occurs in all tissues during growth and repair