Asexual Reproduction
What are the asexual reproduction processes that occur in prokaryotes compared to eukaryotes?
Prokaryotes: Binary fission
Eukaryotes: Mitosis
Describe the process of fertilisation?
The joining of two different haploid gametes to form a diploid zygote that is genetically unique.
What are the two types of reproductive cloning techniques we have studied this term?
Somatic Cell Nuclear Transfer
Embryo Splitting
What are the biological advantages and disadvantages of asexual reproduction?
Advantage:
1. Time: Quick
2. Energy: Low
3. Number of offspring: Lots
4. Adapted to particular favourable conditions
Disadvantage:
1. Limited genetic variation (clones)
2. Competition for same resources
3. Susceptible to infection or extinction if their is drastic change to the once favourable conditions
What are gametes? Provide examples.
Gametes are special reproductive cells used in sexual reproduction.
Egg (female) and Sperm (male)
How is cloning used for agricultural benefits (refer to animals)
Improving livestock
Method: Animal cloning creates genetically identical copies of elite animals using techniques like somatic cell nuclear transfer (SCNT) or embryo splitting.
Benefit: Farmers can produce high-quality milk, meat, or wool consistently.
Example: Cloning cows with high milk production ensures offspring produce similar amounts.
Name the 6 types of asexual reproduction?
1. Budding
2. Fission
3. Fragmentation
4. Vegetative propogation
5. Sport formation
6. Parthenogenesis
Biological advantages of sexual reproduction?
1. Genetic variation: Inherit a mix of genes from both parents. Helps adapt to changing environments.
2. Adapt better to environmental changes.
3. Eliminate harmful mutations (recombination)
4. Disease resistance: Less likely for all members of the same genetic history to gain the same disease (immunity).
How is cloning used for agricultural benefits (refer to vegetables)
Producing genetically identical plants
Method (vegetative propagation): Plant cloning is done through cuttings, tissue culture, or grafting.
Benefit: Farmers can reproduce plants with desirable traits like high yield, disease resistance, or better taste.
Example: Banana and potato varieties are often cloned because they retain the same quality as the parent plant.
Explain the process of fragmentation?
Parent organism is intact – The organism starts as a single individual.
Fragment formation – A part of the organism (could be due to natural shedding, injury, or deliberate breaking) becomes separated. These fragments contain cells capable of regeneration.
Regeneration of missing parts – Each fragment grows the missing structures through cell division and differentiation. For example, a fragment of a starfish arm can regenerate the rest of the starfish under the right conditions.
Independent organism – Eventually, each fragment develops into a fully functional organism, genetically identical to the parent.
Time and energy consuming:
- Need to find a mate
- Need to engage in sexual intercourse (fertilisation is not always successful).
- Need to find a safe breeding ground
- Take care of offspring post birth.
Describe the step by step process of embryo splitting?
Fertilization
A female’s egg is fertilised by sperm in vitro (outside the body) to form a zygote.
Early Cell Division
The zygote divides several times, forming an early-stage embryo (usually at the 2–8 cell stage).
Splitting the Embryo
The early-stage embryo is carefully split into two or more separate groups of cells. Each group can then develop independently.
Development of Identical Embryos
Each split embryo is placed into a surrogate mother or cultured further. They grow into genetically identical offspring.
Explain the process of parthenogenesis?
Parthenogenesis is a type of asexual reproduction in which an offspring develops from an unfertilized egg. In other words, no sperm is involved.
Key points:
Offspring are usually clones of the mother.
In species like bees, it produces male drones from unfertilized eggs.
During meiosis in humans, each diploid cell produces gametes with half the chromosome number. Explain how independent assortment and crossing over during meiosis contribute to genetic variation in gametes, and why this variation is important for the survival of a species.
Crossing Over
During meiosis, chromosomes swap pieces of DNA.
This mixes genes, so gametes aren’t identical to the parent.
Independent Assortment
Chromosomes line up randomly before being separated.
Each gamete gets a different mix of maternal and paternal chromosomes.
Why it matters
Makes offspring genetically unique.
Helps the species adapt and survive in changing environments.
Describe the process of Somatic Cell Nuclear Transfer?
Take a somatic cell – Collect a body cell from the animal you want to clone (e.g., a cow with high milk yield). This cell contains the complete DNA of the donor.
Prepare an egg cell – Obtain an egg from a surrogate mother and remove its nucleus (enucleation), so it no longer contains DNA.
Insert donor nucleus – Transfer the nucleus from the somatic cell into the enucleated egg.
Stimulate cell division – Use an electric shock or chemical signal to make the egg start dividing, forming an embryo.
Implant the embryo – Place the developing embryo into the uterus of a surrogate mother.
Clone is born – The offspring that develops is genetically identical to the animal that donated the somatic cell.