TOPIC 2-Chap 2.4

Question 1

Gametes are Haploid/Diploid. Body cells are haploid/diploid.

Answer 1

Gametes are Haploid. Body cells are diploid.

Question 2

what is a non disjunction of chromosomes

Answer 2

a whole chromosome mutation where there are too little or too many chromosomes

Question 3

identify and describe 4 types of non disjunction of chromosomes

Answer 3

Aneuploidy-situation where a cell either lacks a whole chromosome or has more than 2 of a chromosome

Monosomy-only one member of a homologous pair present from a normal gamete

Polysomy-three or more rather than 2 chromosomes of a particular type

Trisomy-one extra chromosome

Question 4

an example of a monosomy mutation is

Answer 4

Turner syndrome only one X chromosome from Ovum

Question 5

Sexual reproduction occurs when 2 haploid nuclei fuse to form a new _______ cell called a _________.This process is called ________.

Answer 5

Sexual reproduction occurs when 2 haploid nuclei fuse to form a new diploid cell called a zygote. This process is called fertilisation.

Question 6

In animal cells sex organs that are permanent are usually called ________

Answer 6

In animal cells sex organs that are permanent are usually called the gonads

Question 7

The male sex organ OF FLOWERING PLANTS is called ______.The female one is _______.The male gametes are ________ and the female gametes are ________.

Answer 7

The male sex organ OF FLOWERING PLANTS is called anthers. The female one is ovaries. The male gametes are pollen and the female gametes are ovules.

Question 8

IN ANIMALS the male gonads are the ________, which produce the gametes known as sperm/spermatozoa.

The female gonads are called _________ producing female gametes called _____

Answer 8

IN ANIMALS the male gonads are the testes, which produce the gametes known as sperm/spermatozoa.

The female gonads are called ovaries, producing female gametes called ovas .

Question 9

Describe the process of meiosis

Answer 9

Prophase 1-
each chromosome appears in condensed form with 2 chromatids.Homologous pairs of chromosomes associate with eachother. Crossing over occurs at the chiasmata

Metaphase 1-
the spindle forms and the pairs of chromosomes line up on the metaphase plate

Anaphase 1-
the centromeres do not divide. One chromosome (a pair of chromatids) from each homologous pair moves to each end of the cell. As a result the chromosome number in each cell is half of the original.

Telophase 1-
the nuclear membrane reforms and the cell begins to divide. In some cells this continues to full cytokinesis and there may be a period of brief or prolonged interphase. During this interphase there is NO FURTHER REPLICATION OF DNA.

Metaphase 2-
new spindles are formed and the chromosomes still made up of pairs of chromatids line up on the metaphase plate.

Anaphase 2-
the centromeres now divide and the chromatids move to the opposite ends of the cell

Telophase 2-
nuclear envelope re forms, the chromosomes return to their interphase state and cytokinesis occurs giving four daughter cells each with half the chromosome number of the original diploid cell.

Question 10

Variation is introduced in 2 ways during meiosis - identify and describe

Answer 10

Independent assortment (random assortment)
the chromosomes that came from the individual parents are distributed into the gametes

Crossing over (recombination)
process that takes place when large multi-enzyme complexes cut and join bits of the maternal and paternal chromatids together. The points where the chromatids break are called the chiasmata.

Question 11

define diploid and haploid

Answer 11

diploid- a cell with a nucleus containing 2 full sets of chromosomes

haploid-a cell with a nucleus containing one complete set of chromosomes.

Question 12

define homologous chromosomes

Answer 12

a set of one maternal chromosome and one paternal chromosome that pair up during meiotic cell division

Question 13

define translocation in terms of mutations

Answer 13

a mutation where part from one chromosome breaks off and re-joins to another completely different chromosome. It is balanced when part of 2 chromosomes swap

Question 14

Chemicals that are likely to increase the rate of mutation are called ________

Answer 14

Chemicals that are likely to increase the rate of mutation are called mutagens

Question 15

define gametogenesis

Answer 15

gametogenesis is the formation of the gametes by meiosis in the organs

Question 16

what are primordial germ cells

Answer 16

the cells that divide by meiosis to ultimately form the sperm and ova

Question 17

define spermatogenesis

Answer 17

the formation of the sperm in the testes

Question 18

purpose of oogenesis

Answer 18

to form the ova in the ovaries.

Question 19

what is external fertilisation

Answer 19

the process of fertilisation in which the female and male gametes are released outside of the parental bodies to meet and fuse in the environment. Typical in aquatic animals.

Question 20

what is internal fertilisation

Answer 20

the fertilisation of the female gamete which takes place inside the body of the mother

Question 21

define mating

Answer 21

the process by which a male animal transfers sperm from his body directly into the body of the female

Question 22

Outline the process of spermatogenesis

Answer 22

DIPLOID primordial germ cell divides by mitosis to form DIPLOID spermatogonia.

These grow until they are big enough to be called primary spermatocytes

Meiosis- the first miotic division results in 2 HAPLOID cells called secondary spermatocytes

Second Meiotic division results in 4 HAPLOID cells called spermatids

Spermatids then differentiate in the tubules of the testes to form spermatozoa

Question 23

Outline the process of Oogenesis

Answer 23

diploid primordial germ cell divides by mitosis to form diploid oogonia—->Most of the oogonia do not develop further but instead degenerate.

the one that develops and grows is then called the primary oocyte

Oocyte then undergoes meiosis resulting in 2 cells of unequal size called the secondary oocyte (larger one) and the first polar body.

after ovulation meiosis 2 takes place resulting in one HAPLOID ovum and 3 polar bodies

Question 24

Adaptations of spermatoza

Answer 24

ACROSOME- contains digestive enzyme which can digest the layers of the ovum allowing the sperm head to penetrate.

MIDDLE PIECE- mitochondria tightly packed to provide sperm with ATP for the lashing of the tail

TAIL- allow for sperm to swim towards the egg

ALKALINE Semen- vagina is acidic, protects sperm when entering.

NUCLEUS- contains highly condensed haploid chromosomes, this condensed state of the genetic material reduces the amount of energy needed to transport it

Question 25

the layer of protective jelly around the unfertilized ovum is known as . . .

Answer 25

Zona Pellucida

Question 26

__________ is the term used for fertilisation of the ovum in humans.

Answer 26

Conception is the term used for fertilisation of the ovum in humans.

Question 27

when an egg is fertilised by more than one sperm it is known as ___________

Answer 27

when an egg is fertilised by more than one sperm it is know as POLYSPERMY

Question 28

The ___________ ___________ is the tough layer that forms around the fertilised ______ to prevent the entry of other sperm.

Answer 28

The FERTILISATION MEMBRANE is the tough layer that forms around the fertilised OVUM to prevent the entry of other sperm.

Question 29

Outline the process of fertilisation in terms of sperm

Answer 29

sperm approaches oocyte in the oviduct. The acrosome has matured since the sperm left the male reproductive tract

front of sperm touched the zona pellucida of the oocyte and an acrosome reaction is triggered. Enzymes begin to digest layer.

fertilisation happens when the sperm touches the surface of the oocyte and the membranes fuse

sperm’s nucleus quickly decondenses and releases its chromosomes into the oocyte. Meiosis 2 completed forming an ovum.

The male and female chromosomes group together

Cortical granules are released from the oocyte that combines with the zona pellucida to form a tough fertilisation membrane.

Question 30

state and describe the 2 phases of a plant life cycle

Answer 30

sporophyte generation- diploid and produces spores by meiosis

gametophyte generation-haploid, gives rise to the gametes by mitosis

Question 31

Describe gametogenesis of the male gamete (pollen) in flowering plants

Answer 31

Pollen grains carry the male gametes.
Each anther consists of 4 pollen sacs where the pollen grain develops.

Each pollen sac contains a large number of microspore mother cells= diploid —-> they divide by meiosis to form
haploid microspores (the gametophyte generation)

Microgametes are formed from microspores by mitosis- one cell envelops the other to form a pollen grain containing 2 haploid nuclei (generative nucleus and pollen tube)

The tube nucleus produces the pollen tube which penetrates through the stigma, style and ovary and into the ovule.

The generative nucleus then fuses with the nucleus of the ovule to form a new individual.