Inherited Change

Question 1

Describe differences between spermatogenesis and oogenesis

Answer 1

Spermatogenesis = continuous after puberty
Millions produced. 4 sperm per meiosis . No polar bodies all mitotic products used. Complete meiosis on release. Primary spermatocyte smaller than primary oocyte
Products need to differentiate
Requires testosterone

Oogenesis

• in cycles after puberty
• one/ a few per cycle
• 1 ovum per meiosis
• polar bodies
• many mitotic products/ less mitotic replication
• completes meiosis after ovulation
• primary oocyte larger than primary spermatocyte
• no differentiation of products
• requires oestrogen

Question 2

State which parts of spermatogenesis are n and which are 2n

Answer 2

Spermatogonium = 2n
Primary spermatocyte = 2n
Secondary spermatocyte = n
Spermatid = n
Spermatozoan = n

Question 3

What processes take place going from spermatogonium to primary spermatocyte?

Answer 3

Mitosis

Question 4

What process takes place going from spermatid to spermatozoa?

Answer 4

Maturation

Question 5

State one role of a sertoli cell

Answer 5

Provide nutrients for spermatid
Protect spermatid from attack from the immune system
Regulation of sperm production

Question 6

Outline the treatment needed to produce mature oocytes as part of an IVF procedure

Answer 6

FSH hormone given to stimulate follicle development
GnRH agonists prevent LH surge and therefore prevent ovulation
Human chorionic gonadotrophin hormone given to stimulate maturation of oocytes
Mature oocytes collected from ovaries just before ovulation
Use of fine tube/ needle/ ultrasound

Question 7

Describe the roles of centrioles in animal cells

Answer 7

During meiosis/ mitosis/ nuclear division
Replicate before/ after each division
Move to poles
Assemble/ organise microtubules
Centre for growth of spindle fibres/ for formation of spindle
Modified centrioles found elsewhere such as flagella/ cilia

Question 8

Suggest how the difference in the base sequence of the tga 1 gene shown could cause large difference in phenotypes

Answer 8

Change to primary structure/ secondary structure/ tertiary structure/ 3D shape
Enzyme cannot carry out its normal function
Could be an enzyme that is essential for a metabolic pathway
Control the expression of another gene

Question 9

Describe how secondary spermatocyte is produce from spermatogonium

Answer 9

Spermatogonium undergoes mitosis 
Spermatogonium increases in size 
Becomes a primary spermatocyte 
Primary spermatocyte undergoes meiosis I
Forms secondary spermatocyte 
Chromosome number halves

Question 10

Explain the term sex linkage

Answer 10

Allele carried on the X chromosome