B6 Flashcards
Explain how antibiotic resistance can occur.
- Mutations in bacteria produce new strains. 2. Some of the new strains might be resistant to the antibiotics so will not die. 3. They can then reproduce meaning the population of new strains will increase. 4. The resistant strain then spreads.
Give two ways in which plant crops have been genetically engineered.
To be resistant to diseases and to produce bigger / better fruits.
When does extinction occur?
When there are no organisms of a species still left alive.
Give the main steps in adult cell cloning.
- The nucleus is removed from an unfertilised egg cell. 2. Nucleus from an adult body cell is inserted into the egg cell. 3. An electric shock stimulates the egg cell to divide and form an embryo. 4. This embryo will contain the same genetic information as the adult cell. 5. Then the embryo develops further and is inserted in the womb of a woman.
Give the main steps in genetic engineering.
Enzymes are used to isolate the desired gene. The gene is inserted into a vector. The vector is used to insert the gene into cells.
How have bacterial cells been genetically engineered?
To produce useful substances like insulin to treat diabetes.
Explain how evolution occurs through natural selection.
- Random mutations cause variations. 2. Due to variations in a certain trait - some members of the population will be better suited to their environment and survive. 3. They can then reproduce pass on that specific trait. 4. This will continue for generations resulting in most of the population having this specific trait.
Give two concerns with genetically modifying crops.
The effect on populations of wild flowers and insects is unknown. The effects of eating genetically modified food on human health have not been fully researched.
Define tissue culture.
Using small groups of cells from part of a plant to grow identical new plants. (like Mr Evan’s tree)
Give three causes of variation in an organism.
The genes an organism has inherited. The conditions in which the organism has developed. Or a combination.
Define genetic engineering.
Process by which the genome of an organism is modified by introducing a gene from a different ogranism to give a desired characteristic.
Define embryo transplant.
Removing cells from a developing animal (that’s not specialised yet) and then transplanting the embryos into the host mothers.
Describe Jean-Baptiste Lamarck’s theory of evolution.
The changes that occur in an organism during its life can be inherited.
Define evolution.
A change in the inherited characteristics of a population over time - through natural selection - which may result in a new and different species.
State the three possible effects that a mutation could have on phenotype.
No effect. Slightly alter phenotype. Completely change phenotype.
What does meiosis produce?
4 non - identical daughter cells.
What does mitosis produce?
2 identical daughter cells.
Where does mitosis occur?
Everywhere except the games.
Where does meiosis occur?
The gametes.
What happens in sexual reproduction in animals?
Male sperm and female egg cells join (fuse)
What happens in sexual reproduction in plants?
Pollen and egg cells join (fuse)
What happens in sexual reproduction?
There is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
What happens in asexual reproduction?
It involves only one parent and therefore no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
What are diploid cells?
Cells which have chromosomes in pairs. E.g. we have 23 pairs.
What are haploid cells?
Haploid cells have only one copy of each chromosome. E.g. the gametes
How does meiosis happen?
Starts with 46 chromosomes (23 from father and 23 from mother). Copies of the genetic information is made (92 chromosomes). The cell divides twice to form four gametes, each with 23 chromosomes (haploid) All gametes are genetically different from each other
What is fertilisation?
Fertilisation is the fusion of the nucleus of a male gamete with the nucleus of a female gamete.
What happens in fertilisation?
In humans, each gamete has 23 chromosomes. When the two gametes combine, they merge the two sets of chromosome to have 46 (diploid). The new cell divides by mitosis. The number of cells increases. This produces a new cell called a zygote; which will mature into an embryo and then cells begin to differentiate.
3 advantages of sexual reproduction
- Produces variation in the offspring. 2. If the environment changes variation gives a survival advantage by natural selection. 3. Natural selection can be sped up by humans in selective breeding to increase food production.
4 advantages of asexual reproduction
- Only one parent needed. 2. More time and energy efficient as do not need to find a mate. 3. Faster than sexual reproduction. 4. Many identical offspring can be produced when conditions are favourable.
4 disadvantages of sexual reproduction
- Need to find a mate. 2. Not energy and time efficient for this. 3. Really slow e.g. 9 month pregnancy. 4. Not possible for an isolated mate
3 disadvantages of asexual reproduction
- It does not lead to variation in a population. 2. The species may only be suited to one habitat (climate change worsening). 3. Disease may affect all the individuals in a population.
Some organisms reproduce by both methods depending on the circumstances, give 3 examples.
- Malarial parasites reproduce asexually in the human host, but sexually in the mosquito. 2. Many fungi reproduce asexually by spores but also reproduce sexually to give variation. 3. Many plants produce seeds sexually; but also reproduce asexually by runners such as strawberry plant, or bulb division such as daffodils.
Define genome.
The genome of an organism is the entire genetic material of that organism.
Describe the structure of DNA.
DNA is a polymer - a large and complex molecule. It is made up of two strands forming a double helix. It’s in the chromosomes.
What is DNA?
It carries the genetic code which determines the characteristics of a living organism.
What is a gene?
A gene is a small section of DNA in a chromosome. Each gene codes for a particular sequence of amino acids in order to make a specific protein.
Why is it important to study the human genome? (3)
- To search for genes linked to different types of diseases. 2. Understanding and treatment of inherited disorders. 3. Use in tracing human migration patterns from the past
DNA is made up of 4…
Nucleotides
What is a nucleotide made from?
A common sugar and phosphate group with one of four different bases attached to the sugar (A; C; G and T).
How does a codon code for an amino acid and then a protein?
A sequence of three bases is the code for a particular amino acid. The order of bases controls the order in which amino acids are assembled to produce a particular protein.
Write about the structure of DNA.
The long strands of DNA consist of alternating sugar and phosphate sections. Attached to each sugar is one of the four bases. The DNA polymer is made up of repeating nucleotide units.
How does protein synthesis work?
- Gene from DNA is unwound (in the nucleus). 2. One codon codes for a singular amino acid. 3. DNA always stays in nucleus but the info is needed in ribosomes so: - a strand of mRNA copies the strand of DNA (transcription) and goes to the ribosomes. - transferRNA links the amino acids (in the cytoplasm) to the mRNA. - particular tRNA for each individual amino acid. - enzymes link amino acids together and then tRNA leaves - this link of amino acids is called a polypeptide chain and it folds in half to form a unique shape.
What is a protein?
A string of amino acids made in ribosomes.
Which bases are paired together?
A and T. C and G
If a change in the DNA happens, how could the protein change?
So; a change in the DNA would give code for a different amino acid. When the mRNA goes to the ribosome; there would mostly be no effect or a slight effect to the protein. There could be a drastic change which means the protein would not form.
Why does the protein fold in half?
It forms a unique shape which enables them to do their job as enzymes; hormones or forming structures like collagen.
What could happen to the structure of the protein is altered?
A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
What can DNA code for other than proteins?
Not all parts of DNA code for proteins. Non-coding parts of DNA can switch genes on and off; so variations in these areas of DNA may affect how genes are expressed.
What is a gamete?
Sex cell; egg or sperm
What is a chromosome?
Thread - like structure of DNA
What is an allele?
Different forms of a gene
What is a dominant allele?
A form of a gene that is fully expressed; even when two different alleles are present
What is a recessive allele?
An allele that is masked when a dominant allele is present.
What does homozygous mean?
Two of the same alleles.
What does heterozygous mean?
2 different alleles.
What does genotype mean?
The alleles that an organism has for a particular characteristic; usually written as letters.
What does phenotype mean?
Phenotype is the visible characteristics of an organism which occur as a result of its genes.
Examples that are controlled by a single gene.
Some characteristics are controlled by a single gene, such as: fur colour in mice; and red-green colour blindness in humans.
How are some diseases inherited?
They inherit certain alleles.
Give 2 examples of inherited diseases.
Polydactyly and Cystic fibrosis
What is Polydactyly?
A disorder where you have extra fingers or toes.
What is Polydactyly caused by?
Dominant allele
What is Cystic fibrosis?
Disorder that affects cell membranes.
What is Cystic fibrosis caused by?
Recessive allele
For embryonic screening (3)
- Could help stop suffering. 2. Laws in place which protect it from going too far e.g. for the sex of the baby. 3. Eases government and tax payers’ money for treatment in the future.
Against embryonic screening (4)
- In the future people may want an ideal perfect child. 2. Implies that people with disorders are undesirable. 3. Screening can be expensive. 4. Religious / ethical reasons - what if they were wrong and they just killed an innocent human?
How many chromosomes in an ordinary human cell?
23 pairs (46)
How many chromosomes control characteristics?
22 pairs (44)
How many chromosomes carry the gene to determine sex?
1 pair (2)
In females what are the chromosomes?
XX
In males what are the chromosomes?
XY
What effects could mutations have on the phenotype? (3)
None. A slight change or a vast change (very rarely)
What happens if 2 populations have become really different?
If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species.
What is selective breeding?
Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
How does selective breeding work?
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.
Examples of useful selective breeding. (3)
- Disease resistance in food crops. 2. Animals which produce more meat or milk. 3. Large or unusual flowers.
What can happen if selective breeding happens too much?
It can lead to inbreeding where some breeds are particularly prone to disease or inherited defects.
What is an example of how selective breeding has gone wrong?
Pugs can’t see properly.
What does the theory of evolution state?
All species of living things have evolved from simple life forms that first developed more than three billion years ago.
Who was the theory of evolution by?
Charles Darwin
What book did Charles Darwin write?
On the Origin of Species (1859)
Why was the theory of evolution controversial? (3)
- The theory challenged the idea that God made all the animals and plants that live on Earth. 2. There was insufficient evidence at the time the theory was published to convince many scientists. 3. The mechanism of inheritance and variation was not known until 50 years after the theory was published.
Who was Alfred Wallace?
Great admirer of Darwin he produced journals which was evidence for Darwin’s theory. They worked together to publish their scientific discoveries in 1858. He is best known for his work on warning colouration in animals and his theory of speciation
What did Gregor Mendel do?
In the mid-19th century Gregor Mendel carried out breeding experiments on pea plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ (genes) that are passed on to descendants unchanged.
What’s the evidence for evolution? (2)
Fossils and Antibiotic resistance in bacteria
What are fossils?
Fossils are the ‘remains’ of organisms from millions of years ago which are found in rocks.
How can fossils be formed? (3)
- From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent (like oxygen). 2. When parts of the organism are replaced by minerals as they decay. 3. As preserved traces of organisms; such as footprints and burrows and rootlet traces (like in ice).
Why can scientists not be certain about how life began on earth?
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.
What are some factors which could lead to extinction? (5)
- new diseases 2. new predators 3. new and more successful competitors 4. changes to the environment over geological time, such as climate change 5. a single catastrophic event; such as a massive volcanic eruption or a collision between an asteroid and the Earth
Why does bacteria evolve rapidly?
They reproduce at a fast rate.
How do you reduce the amount of bacteria resistant to bacteria? (3)
- doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections. 2. patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains. 3. the agricultural use of antibiotics should be restricted.
Linnaean system acronym
Kids prefer candy over fresh green salad
Linnaean system actual order
Kingdom phylum class order family genus species
Binomial system
Genus, species. E.g. homo sapiens
Who created the 3 domain system?
Carl Woese
3 domain system order
- archaea (primitive bacteria usually living in extreme environments). 2. bacteria (true bacteria). 3. eukaryota (which includes protists; fungi; plants and animals).
