15 — modes of reproduction

Question 1

Asexual reproduction

Answer 1

Asexual reproduction is the process that results in the production of genetically identical offspring from one parent, without the fusion of nuclei of gametes.

Question 2

Offspring

Answer 2

refers to children or the next generation.

Question 3

Gametes

Answer 3

Gametes are sex cells (e.g. sperm and ovum) that are produced
by the reproductive organs (e.g. testes and ovaries)

Has 23 chromosomes in human gametes

Question 4

Mitosis

Answer 4

Mitosis is a type of cell division giving rise to genetically identical cells in which the chromosome number is maintained.

Question 5

Parent cell characteristics

Answer 5

• Four chromosomes
• Undergoes DNA replication:
  doubling of chromosomes
• X-shaped chromosomes
  | | | | -> X X X X

Question 6

Number of chromosomes in humans

Answer 6

46 (zygote) (somatic cells)

Question 7

Sister chromatids

Answer 7

Each chromosome consist of two
identical DNA molecules known as
sister chromatids.

Question 8

Centromere

Answer 8

The point where sister chromatids are joined

Question 9

Daughter cell characteristics

Answer 9

• Genetically identical to
  parent cell
• Genetically identical to each
  other

What does it mean by genetically identical?
* Same chromosomes
* Same genes

Question 10

Importance of mitosis

Answer 10

• Asexual reproduction
• Growth in multicellular organisms
• Repair of damaged tissues

Question 11

Examples of asexual reproduction

Answer 11

Stem tube
Rhizome
Runner

Question 12

Advantages and disadvantages of asexual reproduction

Answer 12

A:
1. Only 1 parent required
2. Fusion of gametes not required
3. All the beneficial qualities r passed on to the offspring
4. Faster than sexual reproduction

D:
1. No genetic variation in offspring -> species r not well-adapted to changes in the env (and may go extinct by natural select.)

Question 13

Sexual reproduction

Answer 13

Sexual reproduction is a process involving the fusion of nuclei of haploid female gamete and the nuclei of haploid male gamete to form a diploid zygote. It produces genetically dissimilar offspring from its parents through fertilisation.

Question 14

Meiosis

Answer 14

Meiosis is a type of cell division that gives rise to genetically dissimilar cells in which the chromosome
number is halved due to the separation of homologous
chromosomes.

Question 15

Homologous chromosomes characteristics

Answer 15

• One chromosome from each parent
• Same shape
• Same size
• Same sequence of genes

Question 16

Importance of meiosis

Answer 16

To produce haploid gametes, which are genetically dissimilar from
each other and the parent cell.

Question 17

Mitosis vs meiosis

Answer 17

Similarities:
1. Parent cell has 23 pairs of homologous chromosomes.
2. Parent cell undergoes DNA replication first

Differences:
Mitosis:
Two daughter cells obtained
Meiosis:
Four daughter cells obtained

Mitosis:
Each daughter cell has 23 pairs of
homologous chromosomes. It is diploid.
Meiosis:
Each daughter cell has 23 chromosomes. It is haploid.

Mitosis:
Daughter cells are genetically identical to each other and to the parent cell.
Meiosis:
Daughter cells are genetically dissimilar to one another and to the parent cell.

Question 18

Advantages and disadvantages of sexual reproduction

Answer 18

Advantages:
1. Offspring may inherit beneficial qualities from both parents
2. There is greater genetic variation in the offspring. This leads to species that r better-adapted to changes in the env

Disadvantages:
1. 2 parents r required (uses more energy)
2. Fusion of nuclei of gametes is required (uses more energy)
3. Method of reproduction is slower

Question 19

Differences betw asexual and sexual reproduction

Answer 19

A: does not involve fusion of nuclei of gametes
S: involves the fusion between haploid nuclei of male gamete and female gamete to form a diploid zygote

A: only 1 parent required
S: requires 2 parents

A: offspring r genetically identical;
S: offspring r genetically diff

A: relatively quicker method to produce offspring
S: slower method to produce offspring

A: involves mitosis
S: involves meiosis in production of haploid gametes

Question 20

Tissue culture of plants

Answer 20

New plantlets are grown from
some plant tissues in a special
growth medium via asexual reproduction

Question 21

Describe the early dev of the zygote aft fertilisation has taken place

Answer 21

The fertilised egg, zygote continues to divide by mitosis to form a ball of cells called an embryo. [1] The embryo travel / move down the oviduct into the uterus by the
contraction of the oviduct muscles via peristalsis [1] and with the help of the cilia. [1]
Implants itself into the uterine lining/uterus wall. [1]

Question 22

Define fertilisation

Answer 22

Fertilisation - fusion of haploid nucleus of a male gamete and haploid nucleus of a female gamete [1] to form a diploid zygote. [1]

Question 23

Mutation

Answer 23

A sudden or spontaneous change in gene structure of chromosome structure or number.