Topic 6 - Inheritance Flashcards
Where is genetic material stored?
The nucleus
What is the structure of DNA?
Double helix structure
What is a chromosome?
A 3D structure containing DNA
What is a gene?
A small section of DNA that codes for a sequence of amino acids to make a specific protein
What is a genome?
The entire genetic material for an organism
Why is it important to understand the genome?
To find genes which are linked to diseases , to treat inherited disorders and to understanding human migration patterns
What type of molecule is DNA
A polymer made from 4 types of nucleotide
What is a nucleotide made up of?
A sugar, phosphate and base
What provides the code for an amino acid
Three nucleotides code for one amino acid
Explain why most mutations do not result in non-functioning enzymes
Some DNA is non-coding therefore some genetic mutations will not result in changes to the phenotype
Which bases pair together?
A + T
C + G
Define sexual reproduction
Reproduction using gametes
Define asexual reproduction
Reproduction without using the gametes and creating a clone
What is a gamete?
A sex cell
What are the gametes in plants?
Male - pollen
Female - egg
What are the gametes in animals?
Male - sperm
Female - egg
Which type of reproduction leads to variation within offspring?
Sexual reproduction
How do you describe the offspring of asexual reproduction?
Clones
What is meiosis?
Cell division producing genetically different gametes
Why is meiosis important?
It will produce 4 gametes which are unique
Outline the process of meiosis
- Genetic information of cell in reproductive organ is copied.
- Cell divides twice.
- 4 genetically different gametes produced with single set of chromosomes
Name some organisms which can reproduce both sexually and asexually
Malarial parasites reproduce asexually in humans, but sexually in the mosquito.
Fungi reproduce asexually by spores, but also sexually to give variation. Many plants produce seeds sexually, but also reproduce asexually by runner or bulb division.
What is the difference between mitosis and meiosis ?
Mitosis produces 2 identical daughter cells but meiosis creates 4 gametes
Name some advantages of sexual reproduction
- produces variation in offspring, meaning a survival advantage if there is an environmental change, also can be used to human advantage in selective breeding.
Name some advantages of asexual reproduction
- Only one parent is needed, more time and energy efficient as organisms, faster the sexual reproduction, many identical offspring can be produced
How many chromosomes are there in a human body cell?
23 pairs, 46 individual
What does the 23 pair of chromosomes determine ?
Sex
What are the sex chromosomes for a female ?
XX
What are the sex chromosomes for a male ?
XY
List two things controlled by a single gene
-Eye colour
-Fur colour in mice
What is an allele?
Different forms of the same gene
What is a dominant allele?
An allele that will always be expressed in the phenotype
What is a recessive allele?
An allele that will only be expressed in the phenotype if two copies are present
What is a genotype?
Genotype is the combination of alleles in an organism.
What is a phenotype?
Phenotype is the observable features of an organism.
What is homozygous ?
Homozygous is two copies of the same allele.
What is heterozygous ?
Heterozygous is different copies of the allele.
Describe Gregor Mendel’s experiments
He carried out selective breeding of pea plants to observe the inheritance of characteristics from parents to offspring.
Why was the importance of Mendel’s work not recognised until after his death?
Scientists did not understand his work at the time
What did Gregor Mendel’s studies conclude?
Inheritance of characteristics determined by ‘units’ that are passed on unchanged
List the 2 discoveries which lead to a greater understanding of the significance of Mendel’s “units”
Behaviour of chromosomes in cell division
‘Units’ (now genes) were located on chromosomes
Structure of DNA
What is polydactyly ?
Having extra digits (fingers of toes)
What causes polydactyly?
A dominant allele
What is cystic fibrosis?
The build up of mucus on exchange surfaces
What causes cystic fibrosis?
A recessive allele
What is embryo screening?
Taking a sample from the embryo to determine whether it will suffer from a genetic disorder.
What are two positives of embryo screening?
-Can evaluate the risk to embryo/mother
-Parents can make an informed decision about the suffering/lifestyle of their child
What are two negatives of embryo screening?
-Can lead to infection and harm to embryo
-Ethical implications about terminating unhealthy embryos
What is variation?
Differences in characteristic of individuals in a population
What causes new variants in a population?
Mutation
Name one characteristic which is caused by genetic inheritance alone, one that is caused by the environment and one that could be a combination of the two.
Genetic= blood type
Both= Hair colour
Environment= scars
What is evolution?
A change in the inherited characteristics of a population over time
What does the theory of evolution through natural selection state?
All species of living things have evolved from simple life forms that first developed more than three billion years ago
How does evolution through natural selection occur?
1) Variation within a population
2) Only the best suited to their environment survive
3) Genes for these beneficial phenotypes passed on
Define a species
A group of organisms that can reproduce to produce fertile offspring
How would a new species occur?
When 2 populations become so different that they can no longer breed to form fertile offspring - speciation
How did Darwin come up with the theory of evolution?
1) Observations of different organisms (Galapagos Islands)
2) Experimentation
3) Discussion with other scientists
4) Developing knowledge of fossils and geology
Why was Darwins theory not widely accepted at first?
1) The theory challenged the idea that God made all the animals and plants that live on Earth
2) There was insufficient evidence
3) The mechanism of inheritance and variation was not known until 50 years after the theory was published.
Describe the ideas of Jean-Baptiste Lamarck
Lamarck thought that changes (variation) occured within one lifetime instead of over many generations.
Describe the process of speciation
1) Two populations become isolated from each other.
2) There is natural variation between organisms
3) Different populations have different environments
4) The best suited individuals in each population survive and breed to pass on their alleles.
5) Eventually the phenotypes become so different that the two populations would be unable to reproduce successfully
What evidence do we have for the theory of evolution ?
1) Fossil records
2) Observing antibiotic resistance in bacteria
How are fossils formed?
1) Parts of the organism do not decay
2) Minerals replace non-decomposed parts of the organism.
3) Traces such as footprints, burrow or roots
Why can scientists not be 100% sure about how life on earth started?
Many early organisms were soft bodied so decayed completely. Geological activity has destroyed evidence,
What is extinction?
Where there are no individuals left of a species
Name factors which may lead to extinction
1) Climate change
2) Over hunting/ fishing
3) Introduction of a new species
4) Lack of food source
5) Small population size
Why are bacteria able to evolve rapidly ?
Bacteria reproduce quickly
Name an antibiotic resistant
MRSA
Explain how antibiotic resistance occurs
1) Bacteria are exposed to an antibiotic
2) Mutation causes variation in the bacteria population
3) Some bacteria are resistant to the antibiotic so survive and reproduce
4) Resistant population rises and spreads as people are not immune
What can be done to reduce antibiotic resistance ?
1) Take the full course of antibiotics
2) Stop taking antibiotics when they are not needed
Why is antibiotic resistance such a big problem ?
New treatments are needed to treat resistant strains of bacteria
What is selective breeding?
The process where humans breed plants and animals for particular genetic characteristics
How is selective breeding carried out ?
1) Parents with desired features are selected
2) Parents are forced to breed
3) Offspring have desired features
4) Repeat the process to exagerate the features
Name 4 characteristics that have been chosen for selective breeding
1) Disease resistance
2) Animals that produce more meat/milk
3) Nature of domestic animals
4) Produce large flowers
What is a risk of selective breeding?
Can cause inbreeding which can cause genetic faults or increase the chance of developing certain diseases.
What is genetic engineering ?
A procces where the genome of an organism is modified by introducing a gene from another organism to give a desired characteristic.
Name two ways in which genetic engineering has been beneficial to mankind
1) Disease resistance in crops to produce more/bigger crops
2) Bacteria modified to produce insulin
Outline the process of genetic engineering
1) Desired gene is identified
2) Desired gene is isolated and extracted from cell using enzymes
3) Plasmid (vector) is removed from bacteria
4) Desired gene is inserted into the plasmid
5) Modified plasmid is inserted into the bacterium
6) Modified bacterium now contains the desired gene
What are some reasons why people are concerned about GM crops ?
1) The effect of GM allele on the wild populations
2) Effect on human health has not been fully explored
3) Ethical issues
Give an example of a GM crop
Golden rice - contains extra vitamin A (prevents blindness)
What is tissue culture ?
A small groups of cells from part of a plant taken and used to grow identical new plants
Why is tissue culture important ?
It is used to preserve rare plant species
What are cuttings ?
Cuttings are small parts of the plant taken and regrown to produce an idential plant to the parent.
what are cuttings used for ?
Cutting are used by gardeners to produce plants quickly and cheaply
What is embryo transfer?
The splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
Explain the process of adult cell cloning
1) The nucleus is removed from an egg cell
2) The nucleus from an adult body cell is removed and inserted into empty egg cell
3) Electric shock stimulates the modified egg cell to divide
4) Once the embryo has developed, it is implanted into the womans uterus
What are some positives of cloning?
Can reproduce individuals from a single individual
Can produce required cells/ compounds/ hormones
What are some negatives of cloning?
Does not increase genetic diversity
Can have issues with disease resistance/ inbreeding
Expensive
What is the traditional classification order ?
Kingdom, phylum, class, order, family, genus, species (kids playing chicken on freeways go splat)
What is the binomial system?
There are 2 names (Genus and species) to identify the species
What are the two developments which led to the improvement in classification systems ?
1) Use of microscopic technology
2) Improved understanding of biochemical processes
What are the three domains ?
Archaea, Eukarya, Bacteria
