Biology 4 - Genetics and reproduction (B13 - B15) [B15 incomplete - not required for mock] Flashcards
What are the characteristics of asexual reproduction?
- No fusion of gametes
- A singular parent
- No mixing of genetic information
- Offspring is genetically identical (Clone)
What is the process involved in asexual reproduction?
Only Mitosis
What are the characteristics of sexual reproduction?
- Fusion of male and female gametes formed by meiosis
- Mixing of genetic information (leading to:)
- Non identical offspring
What is meiosis?
Meiosis is a process that results in the formation of male and female gametes - sperm and egg cells in animals, pollen and egg cells in plants.
Describe the meiotic process.
Similarly to mitosis, the genetic information of the cell is copied so that there are for sets of each chromosome. Each chromosome forms a pair of chromatids. The cell then divides twice in quick succession to form four gametes, each with a single set of chromosomes.
What is the difference between mitosis and meiosis?
Mitosis is the formation of two identical cells while meiosis is making non identical gametes that are genetically different each time.
State a different between a gamete and a regular body cell.
Body cells have two sets of chromosomes (mother and father) while gametes have only one.
Why do the gametes only have one set of chromosomes?
Because when they join with the foreign gamete at fertilisation it completes the cell forming two sets.
What happens after gametes join at fertilisation?
The new cell divides by mitosis. The number of cells increases and as the embryo develops, the cells differentiate.
How many chromosomes in a set?
23
How many chromosomes in a full body cell?
46 as it contains two sets of 23.
How does sexual reproduction produce variation that helps survival?
Through natural selection if the environment changes. Natural selection is sped up by humans in selective breeding.
What is natural selection?
The process by which evolution takes place. As only those genetically suited to their environment survive to be able to breed, the genes that cause a tendency towards survival are passed on more frequently.
What is selective breeding?
The selection of animals or plants for breeding that have a required genetic characteristic. This speeds up natural selection.
What are the advantages to asexual reproduction? (4 things)
- It needs only one parent
- It is time and energy efficient
- Often faster than sexual reproduction.
- Many identical offspring or produced when conditions are favourable.
How do parasites such as malaria reproduce?
Sexually in their mosquito host and asexually in a human host.
This isn’t a question, I just couldn’t think of a way to make a question out of the statement that many organisms reproduce both sexually and a sexually depending on circumstances.
Some organisms depend on both asexual and sexual reproduction depending on the circumstances.
What is the genome of an organism?
The entire genetic material of that organism.
What does DNA stand for?
Deoxyribonucleic acid (Solid tongue twister innit)
What does DNA stand for?
Ribonucleic acid.
What is the genetic material in the nucleus of a cell composed of?
DNA.
What is DNA?
A polymer made up of two strands forming a double helix. A polymer is a substance made of very large molecules made up of many repeating units.
What is a gene?
A small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
What are the 4 bases of DNA?
Adenine, Guanine, Cytosine, Thymine.
AGCT
What does each base pair with?
Cytosine with Guanine. Thymine with Adenine.
CG and AT.
What is a nucleotide?
The combination of a sugar, a phosphate and a base which pair with another nucleotide on their opposite side of the helix.
Where does ribonucleic acid reside?
In the ribosomes.
How does protein synthesis take place?
The ribonucleic acid (RNA) codes for different amino acids which bond to form proteins.
What codes for a specific amino acid?
The combination of three bases along one strand of the double helix.
What part of protein synthesis determines which proteins are made.
The order of the bases controls the order in which amino acids are assembled to produce a particular protein.
How does ribonucleic acid (RNA) code for different amino acids?
The strand of DNA is read by the RNA strand which responds to the different triplets. Once given this information it forms amino acids.
What happens when a protein chain is complete?
It folds up to form a unique shape that enables the protein to carry out its function in the cell.
What is gene expression?
A gene is expressed when it starts making a protein.
How does mutation occur?
When a change in the DNA structure alters the protein synthesised by the gene. Most mutations don’t alter the protein enough to change the function.
When does mutation change the protein function?
When it changes the protein enough to alter the shape of the finished chain.
What are alleles?
Gene that codes for a specific protein. (e.g : Skin colour)
What is a homozygote?
An individual with two identical alleles for a specific characteristic.
What is a heterozygote?
An individual with two different alleles for a specific characteristic.
What is a genotype?
This describes the alleles present or genetic makeup of an individual for a particular characteristic.
What is a phenotype?
The physical manifestation of the genotype regarding a particular characteristic.
What is the difference between the phenotype and the genotype?
The genotype is the alleles that an individual has for a certain characteristic, the phenotype is the one that is physically expressed.
Explain how the phenotype expresses only one of the alleles
If the genotype contains a dominant and recessive allele, then the dominant will be expressed in the phenotype. The recessive allele will only be expressed if two copies are present.
Give the male and female chromosome combinations.
Male : XY
Female : XX
What is Polydactyly?
A dominant phenotype that causes someone to have an extra finger.
What is Cystic fibrosis?
A recessive phenotype that affects organs of the body.
What is variation (genetics)
The differences in the characteristics of individuals in a population.
What are the two main causes of variation?
- Genetic variation
- Environmental variation
What is the theory of evolution by natural selection?
All species of living things have evolved from simple life forms that first developed over 3 years ago.
How is the development of a new species tested and defined?
The two species can no longer breed to form fertile offspring.
What is selective breeding?
A process where humans breed plants and animals for desired characteristics.
Give an example of a problem that can occur with selective breeding?
Defects in some animals due to lack of variation.
What is genetic engineering?
Genes can be transferred to the cells of animals and plants at an early stage of their development so they develop desired characteristics.
Name 3 forms of cloning
- Tissue culture
- Cutting
- Transplanting cloned embryos
How does tissue culture cloning work?
Using small groups of cells taken from part of a plant to grow identical new plants.
How does cutting cloning work?
Answer goes here
How does embryo transplant cloning work?
Splitting apart cells from a developing animal embryo before they become specialised and then transplanting the identical embryos into host mothers.
What is the process of adult cell cloning?
- The nucleus is removed from an unfertilised egg cell.
- The nucleus from an adult body cell, such as a skin cell, is inserted into the empty egg cell.
- A small electric shock stimulates the egg cell to start mitosis.
- Once the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue development.
Name 4 benefits of genetic engineering
- Improved growth rates of plants and animals
- Increased food value of crops, as genetically modified (GM) crops usually have much bigger yields than ordinary crops.
- Crops can be designed to grow well in dry, hot, or cold parts of the world
- Crops can be engineered to produce plants that make their own pesticide or are resistant to the herbicides used to control weeds.
Name 4 concerns about genetic engineering
- Genetic engineering is a new science, so the long term effects have not been confirmed (insects may become pesticide resistant if they continue to eat a diet of pesticide resistant crops)
- Effect of eating GM food for humans.
- Genes from GM plants and animals might spread into wildlife of the countryside.
- May set a dangerous precedent for human genetic engineering, which is ethically controversial.
