Topic 11 - Asexual And Sexual Reproduction

Question 1

What is asexual reproduction?

Answer 1

A process where new cells or organisms are produced without the fusion of gametes.

Question 2

What are the advantages and disadvantages of asexual reproduction?

Answer 2

ADVANTAGE - large number of individuals created quickly, ideal for unchanging environnement.

DISADVANTAGE - lacks genetic variation in population

Question 3

What is sexual reproduction?

Answer 3

Process where new individuals formed from fusion of gametes and pollen to form a zygote.

Question 4

What are the advantages and disadvantages of sexual reproduction?

Answer 4

ADVANTAGES: provides genetic variation

DISADVANTAGES: energy expended in finding a mate, slower, signals sent to prospective mate may attract predators.

Question 5

Describe asexual reproduction in prokaryotes.

Answer 5

BINARY FISSION

• contain one circular molecule of DNA
• binary fission simpler and faster
• occurs in 20 minutes
• exponential growth

Question 6

Describe budding.

Answer 6

Unequal cytoplasm division, new organism grows on parent and breaks away.

Question 7

Describe parthenogenesis.

Answer 7

Type of cloning, results in formation of new individuals from unfertilised egg.

Question 8

What is crossing over?

Answer 8

Mutual exchange of pieces of chromosome and genes between homologous chromosomes. Occurs after homologous chromosomes have synapses to form bivalents in prophase I. Crossing over occurs at specific points called chiasmata. Recombination of alleles occurs as a consequence of crossing over. Recombinants are the chromosomes formed.

Question 9

What is regeneration?

Answer 9

Part of organisms breaks off and regenerates into new individual eg flatworms, sea worms, sea stars.

Question 10

What is spore formation?

Answer 10

Spores released into environment and germinate into new individual.

FUNGI

Question 11

What is vegetative propagation?

Answer 11

Runners, rhizomes, tubers, bulbs and suckers.

When cut, the develop into new organisms.

Question 12

Describe embryo cloning.

Answer 12

Female cow given FSH to superovulate, eggs collected and fused with desirable sperm. In vitro fertilisation occurs. 4 cells from 16-cell embryo taken and implanted into 4 surrogate mothers.

Result: each calf born is a clone of its siblings, not either parent.

Question 13

Describe limitations of nuclear transfer.

Answer 13

• low success rate
• few embryos implanted survive to full term
• clones may have abnormalities
• telomeres become shorter - DNA ages faster than the time period from which animal was born

Question 14

What is meiosis?

Answer 14

Meiosis is the process of cell division that results in the production of new cells each containing half the number of chromosomes of original cell.

Question 15

What is the effect of independent assortment?

Answer 15

Creating new combinations of maternal and paternal chromosomes in gametes.

Question 16

Describe the process of somatic cell cloning (nuclear transfer).

Answer 16

From sheep A, cells are taken from udder tissue. Thus, a somatic cell is taken.
From sheep B, eggs are collected after sheep is given FSH to super-ovulate. The nucleus is removed from an egg - enucleated.
The somatic cell from sheep A is fused with sheep B’s enucleated egg. Electric pulse is used.
Egg is then cultured in vitro to a 16 cell embryo.
Embryo is then implanted into surrogate mother, sheep C.
Lamb is born who is genetically identical to sheep A as the nucleus is received from sheep A.

Question 17

What is the function of the centromere?

Answer 17

Joins together the sister chromatids of a double stranded chromosome.
Is the region where the kinetochore is located, attachment site where sister chromatids are pulled apart during Anaphase of Mitosis and Anaphase II of Meiosis.

Question 18

What is an advantage of producing cloned crops and what is a disadvantage?

Answer 18

Farmer knows the genetic composition of the crop. Can select crops to grow for high productivity and desirable traits.

However, crops are genetically identical which is unideal in changing environment. If one crop fails, all the crops fail.

Question 19

What is the effect of crossing over?

Answer 19

The exchange of genetic material occurs at points - chiasmata. Results in recombinant chromatids consisting of paternally and maternally derived DNA creating genetic variation.

Question 20

What is independent assortment?

Answer 20

Where homologous chromosomes randomly align on either side of the metaphase plate during Metaphase I of Meiosis.

Question 21

Name the first stage where Mitosis differs from Meiosis and how so?

Answer 21

Prophase I. In both, chromosomes condense, spindle starts forming from centrioles, nuclear envelope disappears.

In Meiosis, chromosomes attach to nuclear membrane and synapse to form bivalents of homologous pairs. Crossing over and recombination occurs. In mitosis this does not occur.

Question 22

Difference between metaphase I in Meiosis and mitosis?

Answer 22

In Meiosis, homologous chromosomes assort randomly on either side of the metaphase plate.

In mitosis, all chromosomes line up on the metaphase plate. They do not form homologous pairs.

Question 23

Difference between anaphase I in Meiosis and mitosis?

Answer 23

In Meiosis, homologous chromosomes are separated and pulled to either pole of the spindle. Half to one pole and half to the other.

In mitosis, the spindle fibres attach to kinetochores of the centromeres of the chromosomes, and separates the sister chromatids segregating them to opposite poles of the spindle.

Question 24

What is external fertilisation?

Answer 24

Animals release gametes into external environment - fertilisation occurs outside female body.

Produces large numbers of gametes to increase chance of fertilisation.

Question 25

What is internal fertilisation?

Answer 25

Male delivers sperm into reproductive tract of female. Fertilisation is internal.

Energy cost in finding and securing mate for this to occur. Chance of fertilisation however higher if mate found.

Question 26

What is a clone?

Answer 26

Organism that is the exact genetic copy of the organism it obtains its genetic info from.