Meiosis

Question 1

What is asexual and sexual reproduction?

Answer 1

• Asexual: One parent copies itself to form a genetically identical offspiring.
• Sexual: Involves two parents to produce an offspring that is genetically unique.

Question 2

What is the chromosomes of a female and a male?

Answer 2

Female = XX
Male = XY

Question 3

what is a karyotype?

Answer 3

It is a picture of an organism’s chromosome set.

Question 4

1) How many chromosomes do humans have?
2) What are homologous chromosomes?
3) How many pairs of chromosomes are autosomal/somatic and sex chromosomes?
4) how to calculate diploid cells?

Answer 4

1) Humans have 46 chromosomes or 23 pairs of homologous chromosomes
2) Homologous chromosomes are a set of one paternal and one maternal chromosome paired together.
3) 22 pairs are somatic or autosomal ( for body cells), and one pair are sex chromosomes.
4) a diploid cell has two sets of chromosomes and we mark that as 2n (where n is number of homologous pairs) so 2n = 46 where n = 23

Question 5

What are the three types of sexual life cycles?

Answer 5

1) Animal cycle: dominated by diploid cells
2) Fungal cycle: dominated by haploid cells
3) Plant cycle: half of their life cycle is at the haploid stage and the other half is at the diploid stage.

Question 6

Explain Meiosis 1 (cell division):

Answer 6

• The cell is diploid (2n=4) with a single-stranded chromosome
• Interphase 1; The cell grows and replicates chromosomes (becomes double-stranded) and gets ready for cell division.
• Prophase 1: The duplicated chromosomes are condensed
• Metaphase 1: The condensed double-stranded chromosomes are aligned in the middle (on the metaphase plate).
• Anaphase 1: The chromosomes are split apart.
• Telophase 1: The cell splits and is now 2 haploid daughter cells still having duplicated chromosomes.

Question 7

Explain Meiosis II (con’t cell division):

Answer 7

• No interphase occurs between meiosis I and II.
• Prophase II: Chromosomes condense
• Metaphase II: Chromosomes align
• Anaphase II: Chromosomes are pulled apart
• Telophase II and cytokinesis: The cell divide and at the end of meiosis II you end up with 4 haploid daughter cell with a single unduplicated chromosome.

Question 8

What are three sources of genetic variation?

Answer 8

1st) crossing over:
- it happens during prophase I, when synapsis happens ( the physical pairing of two Homologous chromosomes)
- The place where crossing over occurs is the chiasma
- Crossing over is the exchange of segments of non-sister chromatids between a homologous chromosome

2nd) independent assortment:
- Random alignment of each pair of chromosomes at the metaphase plate in Meiosis I.
- 2^n calculates the number of possible combinations between homologous pairs.

3rd) Random fertilization:
- Occurs after meiosis II
- Its where fertilization is random and nobody knows which sperm fertilizes with which egg.