Sexual Reproduction in Mammals

Question 1

What are gametes?

Answer 1

Cells with half the usual chromosome number

Haploid cells

Question 2

What is fertilisation?

Answer 2

The fusion of two gamete nuclei to make a zygote nuclei

Question 3

What is a zygote?

Answer 3

The cell formed from the fusion of two gamete nuclei

Question 4

What is sex?

Answer 4

Has a genetic basis which depends on the activation of the SRY chromosome - activated means male, inactive means female

Question 5

What is gametogenesis?

Answer 5

The production of gametes

Question 6

What are the gonads?

Answer 6

An animal organ where gametes are produced

Question 7

What are the female gonads?

Answer 7

Ovaries

Question 8

What are the male gonads?

Answer 8

Testes

Question 9

What are the female gametes?

Answer 9

Ova

Question 10

What are the male gametes?

Answer 10

Spermatazoa

Question 11

What is the germinal epithelium?

Answer 11

The layer of cells that undergoes regular mitosis

Question 12

Where is the germinal epithelium in females?

Answer 12

Outer layer of the ovaries

Question 13

Where is the germinal epithelium in males?

Answer 13

Seminiferous tube

Question 14

Explain spermatogenesis

Answer 14

Germinal epithelium in seminiferous tube divide by mitosis to form spermatagonium
Grow into primary spermatocytes
Divide by meiosis I to form secondary spermatocyte
Divide by meiosis II to form spermatids
Spermatids mature into spermatazoa

Question 15

Are primary spermatocytes 2n or n?

Answer 15

2n

Question 16

Are secondary spermatocytes 2n or n?

Answer 16

n

Question 17

Are spermatids 2n or n?

Answer 17

n

Question 18

When does spermatagonium occur?

Answer 18

After puberty, producing millions of sperm cells every day throughout adult life

Question 19

What is a Graafian follicle?

Answer 19

A fluid filled sac formed from follicle of cells around the nucleus

Question 20

How often does ovulation occur?

Answer 20

Every 28 days

Question 21

What is a corpus luteum?

Answer 21

When the secondary oocyte leaves the Graafian follicle during ovulation and fills with hormone secreting cells to produce a yellow body

Question 22

When does the corpus luteum degenerate?

Answer 22

When fertilisation does not occur

Question 23

Explain the process of oogenesis

Answer 23

Germinal epithelium of the ovaries divides by mitosis to form oogonium
Oogonium grow into primary oocytes
Primary oocytes divide by meiosis I to form secondary oocyte and a polar body
Meiosis II happens after fertilisation
Primary oocyte divides into secondary oocyte and polar body. OG polar body divides into two polar bodies

Question 24

What is the stimulus needed for secondary oocytes to complete meiosis 2?

Answer 24

Fertilisation

Question 25

Name some differences between oogenesis and spermatogenesis?

Answer 25

Ovum is non-motile, sperm is Oogonium made in the fetus pre-birth, sperm made every day post puberty Four sperm cells made from spermatagonium, one ovum made from an oogonium Ejected by ejaculation vs ovulation Sperm cells reach completion during sperm production, ovum halt at prophase 2

Question 26

What are cortical granules?

Answer 26

Vesicles around the outside of the cytoplasm of the oocyte

Question 27

What is the zona pellucida?

Answer 27

Layer of glycoprotein between cytoplasm and the follicle cells

Question 28

Where is sperm produced?

Answer 28

Seminiferous tubules in the testis

Question 29

What do the Sertoli cells do?

Answer 29

Nourish the sperm cells as they mature

Question 30

What does the head of the sperm contain?

Answer 30

Haploid nucleus and an acrosome

Question 31

What does the middle piece of the sperm contain?

Answer 31

Mitochondria for energy to move

Question 32

What does the tail of the sperm contain?

Answer 32

Microtubules

Question 33

What is the head of the sperm covered in?

Answer 33

Glycoprotein from the epididymus

Question 34

How is the secondary oocyte moved along the oviduct?

Answer 34

Beating action of the cilia on the cells lining the oviduct

Question 35

What is capacitation?

Answer 35

Changes to the head of the sperm which make it fully capable of fertilisation

Question 36

What are the two events which occur during capacitation?

Answer 36

Head stripped of glycoprotein | Acrosome reaction

Question 37

What is the acrosome reaction?

Answer 37

Acrosome swells Fuses to membrane of egg cell Hydrolytic enzymes released by exocytosis Moves through zona pellucida

Question 38

How do sperm get through the zona pellucida?

Answer 38

Enzymes from acrosome reaction hydrolyse the glycoprotein from which the zona pellucida is made

Question 39

What are the three main stages of gametogenesis?

Answer 39

Multiplication Growth Maturation

Question 40

What is spermatogenesis?

Answer 40

Formation of spermatazoa in the testes

Question 41

Are oogonium haploid or diploid?

Answer 41

Diploid

Question 42

Are primary oocytes haploid or diploid?

Answer 42

Diploid

Question 43

Are secondary oocytes haploid or diploid?

Answer 43

Haploid

Question 44

What are the products of oogenesis?

Answer 44

A haploid ovum and three polar bodies

Question 45

What are the adaptations of a sperm cell?

Answer 45

Acrosome - hydrolytic enzymes to break down zona pellucida Mitochondria - ATP for energy for movement Flagellum - movement Haploid nucleus - restore diploid cell number Streamlined - move quickly and efficiently

Question 46

Where does the sperm fertilise the secondary oocyte?

Answer 46

In the upper oviduct

Question 47

What is released from the Graafian follicle during ovulation?

Answer 47

Secondary oocyte

Question 48

When does the acrosome reaction occur?

Answer 48

When the head of the sperm touches the zona pellucida of the egg

Question 49

Name the stages of fertilisation

Answer 49

Acrosome reaction Membrane fusion Cortical reaction Meiosis II

Question 50

Explain what happens during membrane fusion in fertilisation

Answer 50

Membrane of egg and sperm fuse so haploid nuclei can fuse

Question 51

What is the purpose of the cortical reaction?

Answer 51

To stop polyspermy