Cell Replication and Variation

Question 1

How do prokaryotes replicate?

Answer 1

Binary Fission: rapid reproduction producing a new organism from parent

Question 2

What are the phases of mitosis?

Answer 2

1. Interphase - Cell cycle where cell spends most of life
2. Prophase - chromosomes condense so visible - sister chromatids held together by centromere; nuclear membrane breaks down
3. Metaphase - homologous chromosomes align in middle of cell via centromere
4. Anaphase - spindle fibres (from centrioles) pull centromere towards ‘poles’ of cell - splitting sister chromatids
5. Telophase - nuclear membrane reforms around chromosomes at each pole
6. Cytokinesis - cytoplasm divides and two nuclei (forming two cells) - not considered part of mitosis

Question 3

Differentiate between diploid and haploid

Answer 3

Diploid = 2n = 46 (mitosis)
Haploid =n = 23 (meiosis)

Question 4

What are phases of meiosis?

Answer 4

Same as mitosis but repeats

Prophase I - crossing over
Metaphase I - pairs independently assorted ( each side of equator had random number of maternal and paternal chromosomes)

Question 5

How does genetic variation occur?

Answer 5

Independent assortment: assortment of chromosomes in meiosis II. Each chromosome assorted independently of other resulting in variation of possible chromosomes in each cell.

Random fertilisation: One ovum will mature, and millions of sperm cells will mature offering vast variety in chromosomal combinations)

Question 6

Define gametogenesis

Answer 6

Production of gametes

Question 7

Create a table comparing and contrasting oogenesis and spermatogenesis

Answer 7

oogenesis - produces one haploid ovum - the other three are degenerate, oogenesis precursor: oocyte, discontinued process - tightly regulated beginning before birth and is only completed after fertilisation

Both - involve formation of haploid gamete cells from an original diploid cell, precursor cells undergo mitotic division before meiosis can occur, hormones play a crucial role in initiating and controlling both processes

Spermatogenesis - produces 4 x haploid spermatozoa cells, spermatogenesis precursor: spermatocyte, continuous process - begins at puberty

Question 8

State other differences between spermatogenesis and oogenesis

Answer 8

Refer to Table 1 pg217 of the Textbook