Inheitance, Variation And Evolution Flashcards
DNA
genetic material in the nucleus of a cell. Has a double helix structure
A gene
A small section of DNA that codes for a particular sequence of amino acids to form a specific protein
A genome
The entire set of DNA in an organism
Human genome project
Aims to determine the DNA sequence of the entire human genome and record every gene in human beings
Female sex chromosomes
XX
Male sex chromosomes
XY
Gamete
Sex cells
Chromosome
Thread-like structures of DNA that carry genetic information in form of genes. Located in the nucleus
Alleles
Different versions of a particular gene
Dominant allele
An allele that is always expressed, even if only one copy is present
Recessive allele
An allele that is only expressed if 2 copies are present
Homozygous
When 2 alleles of a gene are the same
Heterozygous
When 2 alleles of a gene are different
Genotype
Combination of alleles that control each characteristic
Phenotype
Observable characteristics of an organism e.g. eye colour, hair colour, height, weight
Monohybrid inheritance
Characteristics that are controlled by a single gene which contains two alleles, one allele is inherited from the mother and the other from the father
Four bases of DNA structure
Adenine, thymine, cytosine, guanine
Complementary base pairing
Adenine + thymine, cytosine + guanine
In vitro fertilisation (IVF)
a process of fertilisation where an egg is combined with sperm in a test tube and then the embryos are inserted back into the mother’s uterus.
How does IVF reduce the chances of inherited diseases?
The cells from the embryo can be tested for a genetic disorder before being placed in the mother’s uterus. Therefore you would not implant the affected embryos.
Embryonic screening procedure
When a cell gets taken from the embryo and it’s genes get analysed.
Pros of embryonic screening
Can avoid suffering for the future child, treating inherited disorders cost the government a lot of money, there are laws in place to stop embryonic screening being abused
Cons of embryonic screening
Could imply that people with genetic disorders are ‘undesirable’ which isn’t fair or true, very expensive meaning it isn’t available for everyone, could be abused in the future and used to make a parents dream offspring with chosen characteristics.
Variation
Differences in features between individuals of the same species
The factors for variation:
Genetic factors (the different genes they have inherited)
Environmental factors (different environments that they live in)
A combination of both genetic and environmental
Examples of variation caused by genetics
Eye colour, gender, fingerprints
Examples of variation caused by the environment
Voice + accents, hair length
Examples of variation caused by both environment and genetics
Skin colour, hair colour, height
What causes genetic variations?
Mutations
What is a mutation?
A rare random change in an organism’s DNA that can be inherited
What does speciation mean?
When the phenotype of organisms change so much over time due to natural selection that a completely new species is formed
What is genetic engineering?
Changing the genome of an organism by introducing a gene from another organism to give a desired characteristic
What is the organism receiving genetic material called in genetic engineering?
Genetically modified organisms
What is the DNA of genetically modified organisms known as?
Recombinant DNA
What is the enzyme called that cuts the DNA fragment called in genetic engineering?
Restriction enzyme
What is the enzyme called that sticks DNA fragments to the DNA called in genetic engineering?
DNA ligase
Reasons for extinction
- environment changes too quickly
- new predator kills them all
- a new disease kills them all
- they can’t compete with another species for food
- catastrophic event happens that kills them all
What is selective breeding?
Human’s artificially select the plants or animals that they are going to breed so that the genes for particular characteristics remain in the population
Selective breeding method:
1) select individuals with desirable characteristics and breed them together
2) choose the offspring with the desirable characteristics and breed them together until all offspring have desirable characteristics
Main problems of selective breeding:
- reduces gene pool (number of different alleles in a population)
- inbreeding (farmed keeps breeding from the best - which are closely related) -> leads to health problems as there is more chance of inheriting harmful genetic defects
Cons of genetic engineering
- some say growing GM crops will affect number of wild flowers - reducing biodiversity
- transplanted genes may get into natural environment
- may not be safe long term on human health
Pros of genetic engineering:
- can increase yield of crops
- increase nutritional value
- already being grown in some places without any problems
What are fossils?
Remains of organisms from many thousands of years ago, which are formed in rocks
What do fossils provide evidence of for scientists?
That organisms lived ages ago and tell us a lot about how much or how little organisms have evolved over time
Why are there gaps in fossil records?
- many early life forms were soft-bodied meaning they decay fully
- fossils have been destroyed by geological activity
3 ways fossils form:
- gradual replacement by minerals
- forms casts + impressions
- from preservation in places where no decay happens e.g. it’s too cold in glaciers,
What is MRSA?
a very serious bacterial strain that is resistant to most antibiotics
How should antibiotics be used to prevent antibiotic resistant strains of bacteria developing?
- doctors should not prescribe inappropriately
- patients should complete their course to prevent any bacteria surging and causing resistant strains
- restriction of agriculture use of antibiotics
Why was the three-domain system of classification introduced?
Due to improvement of microscopes and understanding of biochemical processes
Three categories in the three-domain system:
Archaea (bacteria in extreme conditions)
Bacteria (true bacteria)
Eukaryota (Protista, fungi, plants and animals)
Why is the binomial system used to classify organisms?
It is worldwide meaning scientists in all countries and languages refer to a particular species by the same name - avoids confusion
What do evolutionary trees show?
- how closely scientists think species are related to each other
