4.1.2 Cellular Replication and Variation

Question 1

What is the difference between mitosis and meosis

Answer 1

Mitosis is cell divisio for body cells (not dividing all the time)

Meosis produces sex cells (sperm +egg) and results in haploids for fertilisation (n)(cells with half the amount of chromosomes (DNA))

Question 2

What are chromosomes?

Answer 2

A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.

Question 3

When do haploids and diploids occur?

Answer 3

Diploids (2n) are non reproductive cells (all cells except sperm and egg). There have two complete sets of chromosomes

Whereas, haploids (n) (AKA gametes AKA sperm and egg) occur as a result of meoisis and are the individual chromatids (chromosomes separated into two cells)

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Question 4

Describe the process of oogenesis and the final outcomes?

Answer 4

• egg production through meosis (before birth)
• 1 large haploid cell with a lot of nutritional material and 3 small ‘polar bodies’ that disintegrate

Output: 1 gamete

Question 5

Describe the process of spermatogenesis and the final outcomes?

Answer 5

• sperm reproduction
• occurs continuously only after puberty

Output:

gives rise to 4 highly motile haploid sperm cells

Question 6

Contrast and compare spermatogenis and oogenisis

Answer 6

Similarities=

-both are meosis process that result in haploid cells

Differences=

-spermatogenesis produces 4 viable gametes, oogenesis produces 1 viable gamete

Question 7

What are three ways genetic variation can occur?

Answer 7

• independent variation (mutations)
• fertilisation (as two genetics combine)
• genetic crossover