B6 : KO Flashcards
Asexual reproduction
Where 1 parent provides all the genetic information. The offspring is an exact copy (clone) of the parent.
Sexual reproduction
Where 2 parents provide the genetic information. A unique offspring is created.
Gamete
Sex cell.
Meiosis
A special form of cell division that happens in the sexual organs (testes and ovaries) to form gametes.
Haploid
Half the number of chromosomes (compared to normal cell)
Diploid
The normal number of chromosomes found in all cells apart from gametes (and red blood cells)
Fertilisation
The fusion of gametes. It restores the full number of chromosomes.
DNA
A polymer made of 2 strands forming a double helix.
Genome
The entire genetic material of that
organism.
Mutation
Changes in the DNA base pair sequence.
Allele
Different forms of the same gene.
Chromosome
A structure found in the nucleus, made from DNA
Gene
A section of DNA which codes for a specific sequence of amino acids to make a specific protein.
How do sexual and asexual reproduction differ?
Sexual reproduction involves the fusion of gametes and a mixing of genetic information. Asexual reproduction involves only one parent and no fusion of gametes.
What are the gametes called in animals and flowering plants?
Sperm and egg cells in animals and pollen and egg cells in flowering plants.
Compare meiosis to mitosis.
Meiosis has 2 division leading to the chromosome number halving. It forms 4 gametes and only occurs in the sex organs. Mitosis only has one division and forms 2 identical daughter cells. It can happen everywhere else in the body.
What are the advantages of sexual reproduction?
produces variation in the offspring,
if the environment changes variation gives a survival advantage by natural selection, natural selection can be accelerated by humans in selective breeding to increase food production.
What are the advantages of asexual reproduction?
only one parent needed, more time and energy efficient as do not need to find a mate, faster than sexual reproduction, many identical offspring can be produced when conditions are favourable.
Why is understanding the human genome so important?
You can search for genes linked to different types of disease, understand and treat inherited disorders and trace human migration patterns from the past.
Genotype
The alleles present.
Phenotype
The physical expression of the genotype.
Homozygous
If two alleles present are the same e.g. BB or bb
Heterozygous
If two alleles present are different e.g. Bb
Dominant
If a dominant allele is present, its phenotype is always expressed.
Recessive
Both alleles need to be recessive (homozygous recessive) for the recessive phenotype to be expressed.
Variation
Different characteristics within a population.
Evolution
A change in the
inherited characteristics of a population over time through a process of
natural selection which may result in the formation of a new species.
Natural selection
The process where nature selects what characteristics (controlled by genes) are best for organisms to survival in that specific environment and hence allows it to reproduce.
Selective breeding
The process by which humans breed plants and animals for particular desired characteristics.
Genetic engineering
A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
What can cause mutations?
These can happen by accident during DNA replication, or as a result of damage from the environment (for example UV light).
What is polydactyly and what causes it?
A non-life threatening disorder which gives the person extra fingers or toes. It is caused by a dominant allele.
What is cystic fibrosis and what caused it?
A disorder of cell membranes which causes increased mucus in the respiratory and digestive tract. It is very serious and is caused by inheriting 2 recessive alleles.
What types of genetic tests are available throughout a persons life?
Analysis can be carried out at any time throughout your life. Antenatal testing, neonatal testing and pre-implantation genetic diagnosis (PGD) are designed to identify potential disorders as soon as possible.
How many pairs of chromosomes are in a normal human body cell?
23 pairs so 46 in total. 22 control characteristics only and one pair determine sex (XX and XY).
What causes variation?
Genetic factors, environmental factors or a combination of both.
What characteristics could be artificially selected for?
Disease resistance in food crops, animals which produce more meat or milk, to get a gentle nature of domestic animals (eg. dogs), large or unusual flowers
How is selective breeding carried out?
Selective breeding involves choosing parents with the desired
characteristic from a mixed population. They are bred together. From the
offspring those with the desired characteristic are bred together. This
continues over many generations until all the offspring show the desired
characteristic.
Clone
An individual that has been produced through asexual reproduction and is genetically identical to the parent.
Tissue culture
Using small groups of cells from part of a plant to grow identical new plants
Cuttings
An older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
Embryo transplants
Splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
Gregor Mendel
Known as the father of genetics. Carried out experiments with peas in the mid-19th century and determined ‘units’ passed to the future generations.
Charles Darwin
Proposed the theory of evolution by natural selection following years of travel around the world and scientific research.
Jean-Baptiste Lamarck
Proposed an alternative theory of evolution which is not thought to be correct. He proposed changes that occur in an organism during its lifetime can be inherited.
Alfred Russel Wallace
Also proposed the theory of evolution by natural selection and worked with Darwin in the run up to the publication of On the Origin of Species. Known best for his work on speciation and warning colouration in animals.
Speciation
The formation of a new species.
Species
Organisms are the same species if they can interbreed to produce fertile offspring.
Fossils
the ‘remains’ of organisms from millions of years ago, which are found in rocks.
What are the main steps in genetic engineering?
enzymes are used to isolate the required gene, this gene is inserted into a vector, usually a bacterial plasmid or a virus, the vector is used to insert the gene into the required cells, genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
How is adult cell cloning carried out?
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 egg cell.
- An electric shock stimulates the egg cell to divide to form an embryo.
- These embryo cells contain the same genetic information as the adult
skin cell.
- When the embryo has developed into a ball of cells, it is inserted into
the womb of an adult female to continue its development.
Why were Darwin’s ideas not fully accepted at the time?
The theory challenged the idea that God made all the animals and plants that live on Earth. In addition -
- there was insufficient evidence at the time the theory was published to convince many scientists
- the mechanism of inheritance and variation was not known until
50 years after the theory was published.
Extinction
the permanent loss of all members of one species. Can be caused by biotic or abiotic factors.
Mass extinction
the loss of many or most species on Earth. Usually caused by climate change or a single catastrophic event.
Antibiotic resistant bacteria
Cannot be destroyed by most common antibiotics thus posing a significant threat to public health.
Classification
the organisation of living organisms into groups according to similarities
Carl Linnaeus
Developed the Linnaean system of classification - Kingdom, Phylum, Class, Order, Family, Genus, Species
Binomial system
A method of naming organisms using their genus and species names.
Carl Woese
Developed the ‘three-domain system’ of archaea, bacteria and eukaryota
Evolutionary trees
Can be used to show the relationship between different species.
How does speciation occur?
Isolation of a population occurs and then there are different selection pressures on the 2 groups. Genetic variation and mutation will give some organisms a survival advantage and they will reproduce and pass on the favourable allele. Eventually the 2 groups will become so different genetically they will be considered separate species.
How are fossils formed?
- from parts of organisms that have not decayed because one or more
of the conditions needed for decay are absent
- when parts of the organism are replaced by minerals as they decay
- as preserved traces of organisms, such as footprints, burrows and
rootlet traces.
How does the mineralisation of an organism occur which leads to fossilisation?
Organism dies and falls to the ground,
soft parts (eg. flesh) decompose, leaving the bones behind as they are harder to decay. The skeleton is then covered in sand/soil and becomes mineralised (bone tissue replaced by mineral ions) over millions of years and then turns to rock.
Why is the fossil record incomplete?
Many early forms of life were soft-bodied, which means that they
have left few traces behind. What traces there were have been mainly
destroyed by geological activity. This is why scientists cannot be certain
about how life began on Earth.
