Variation Flashcards
What is variation?
Differences in the characteristics of individuals in a population
What is variation caused by?
Inherited genes
Environment in which they have developed
Combination of both of these
What is mutation?
A lot of genetic variation in a species arises from random mutation
Change in DNA sequence
Occur continuously
Very rarely lead to a change in phenotype
What is selective breeding?
Selective breeding is the process by which humans breed plants and animals for particular genetic characteristics
Choose parents with the desired characteristic from a mixed population
Breed them together
Choose offspring with the desired characteristic and breed them
Continue over many generations until all offspring show the desired characteristic
What are examples of characteristics that are chosen for usefulness or appearance?
Disease resistance in food crops
Animals that produce more meat or milk
Domestic dogs with gentle nature
Larger or unusual flowers
Disadvantages of selective breeding
Inbreeding
Reduces variation
What is cloning?
A clone is an individual that has been produced asexually and is genetically identical to its parent. There are several different methods for producing both plant and animal clones , but there are benefits and risks associated with cloning.
How does adult cell cloning work?
Sheep A - nucleus removed from adult cell e.g skin
Sheep B - nucleus removed from mature egg to leave empty egg
Electric shock
Fusion occurs
Divides to start to form an embryo
Embryo implanted into uterus of Sheep C
Lamb born is clone of Sheep A
What is a tissue culture?
Small groups of cells from part of a plant are used to grow identical new plants. This is important for preserving rare plant species and growing plants commercially in nurseries.
What is cutting?
An order simple method, used by gardeners to produce many identical plants from a parent plant.
What is embryo transplant?
Cells split apart from the developing animal embryo before they become specialised, then the identical embryos are transplanted into host mothers.
What are benefits of methods of cloning?
Larger number of identical offspring produced
Quick and economical
Desired characteristics guaranteed
What are risks to methods of cloning?
Limits variation and causes reduction in gene pool
Clones may be vulnerable to diseases or changes in the environment
Ethical considerations around cleaning living organisms
What is genetic engineering?
Is a process that involves changing the genome of an organism by introducing a gene from another organism to produce the desired characteristic
Examples of genetic engineering
Bacterial cells have been genetically engineered to produce useful substances, such as human insulin to treat diabetes
Plant crops have been genetically engineered to be resistant to diseases, insects or herbicides or to produce bigger and better fruit and high yields, crops that have undergone genetic engineering are called genetically modified (GM)
How goes genetic engineering work?
Cell with vector (usually bacterial plasmid or virus)
Vector taken out of cell and split open
Cell from organism with desired gene
Enzymes used to cut out the design gene
Gene is inserted into the vector
Vector used to insert gene into required cell at an early stage in development
As the organism grows it develops with the desired characteristics from the other organism.
What are benefits of genetic engineering?
Potential to overcome some inherited human diseases
Can lead to higher value of crops as GM crops have bigger yields than normal
Crops can be engineered to be resistant to herbicides, make their own pesticides, or be more resistant to environmental conditions
What are risks of genetic engineering?
Genes from GM plants and animals with a spread to other wildlife, which could have devastating effects on ecosystems
Potential negative impacts on populations wildflowers and insects
Ethical concerns, for example, in the future people could manipulate the genes of children to ensure certain characteristics
Some believe the long-term effects on health of eating GM crops have not been fully explored
Why does cell division take place?
Growth
Repair
Replace
What is mitosis known as in bacteria?
Binary fission
What are the different phases of mitosis?
DNA replicates (prophase) and the number of sub-cellular structures increase
The pairs of chromosomes line up in the middle of the cell with spindle fibres attached to the centre of each pair of chromosomes (metaphase)
1 copy of each chromosome is pulled to opposite sides of the cell (anaphase)
Two new identical daughter cells form (telophase)
What is cytokinesis?
Another word for cell division
What is centromere?
Part of a chromosome where sister chromatids are held together
What are chromatids?
Strands of replicated chromosome
What is meiosis?
Cell division that produces gametes
What is a haploid?
A cell with one set of chromosomes
What is a diploid?
A cell with two sets of chromosomes
How does meiosis work?
In a parent cell, chromosomes make identical copies of themselves and sections of DNA get swapped
Pairs of chromosomes divide and then chromosomes divide
What is a gene?
Small section of DNA which makes up chromosomes
Each gene codes for a sequence of amino acids to form a particular protein
These sequences determine our physical characteristics
What is DNA?
A polymer made up of two strands forming a double helix
Forms chromosomes
Four bases of A, C, G, T
What is a mutation?
A change in the DNA code
What are the 3 stages of the cell cycle?
Growth phase
Mitosis
Cytokinesis
Which has pairs go together?
AT
CG
What is triplet code?
Nucleotides read in groups of three?
What is a nucleotide?
Phosphate group (circle)
Sugar (pentagon)
Base A/C/G/T
What is protein synthesis?
Transcription of the gene in the nucleus to form a template strand
Processing of the template
Translation of the template in a ribosome to form an amino acid chain
Modification of the protein
What is the effect of a mutation?
Change in code can be positive, negative, or most commonly neutral
What are introns?
Non-coding sections of DNA
What are exons?
Coding sections of DNA
Can genes be switched on and off depending on the phase of development?
Yes
Depending on which parts of the gene are on determines which proteins are made
What do introns determine?
Phenotype
What is mRNA?
T->A
A->U
C->G
G->C
Carrier complements mRNA template
