Inheritance, Variation And Evolution Flashcards
What are the two types of reproduction?
Sexual reproduction - where two gametes from different parents join together
And
Asexual - which involves only one parent
What type of cell division produces cells for asexual reproduction?
Mitosis produces cells in asexual reproduction, so the offspring are genetically identical (clones) as all the DNA comes from one parent.
What type of cell division produces cells for sexual reproduction?
Meiosis produces gametes for sexual reproduction
How are gametes different to normal cells?
Gametes produced in meiosis or not genetically identical.
Also, they have half the DNA of a normal cell so when they join (fuse) the new cell has the full amount
What are the gametes called in animals?
Sperm cells are the male gametes, and egg cells of the female gametes
What are the gametes is called in flowering plants?
Pollen are the male gametes, and egg cells are the female gametes
What happens during meiosis to make gametes?
The DNA is replicated, copied.
The cell divides twice to go for gamete cells.
Each gamete is slightly different genetically to the other gametes.
Why is it important that gametes are genetically varied?
As each gamete is slightly different to the others, it mean offspring of sexual reproduction are genetically varied too.
This gives species are better survival chance.
Why do gametes have half the DNA of a body cell?
So that when the male and female gametes join during fertilisation, the new cell formed will have the normal chromosome number.
What are the advantages of sexual reproduction?
Offspring show genetic variation, which means that if the environment changes the species has a survival advantage by natural selection.
How do humans take advantage of natural selection?
Humans can take advantage of natural selection as they selectively breed offspring and choose the individuals that will increase food production.
What are the advantages of asexual reproduction?
Only one parent is needed which saves time and energy as no mate needs to be chosen. Also is this faster than sexual reproduction and many identical offspring can be produced.
Do some organisms do sexual and asexual reproduction?
Yes, many plants, fungi, and some parasites take advantage of both types of reproduction
How do plants to do both sexual and asexual reproduction?
Seeds are produced by sexual reproduction, but runners (e.g. in strawberry plants) and bulbs (E.g. daffodils) are produced asexually.
How do fungi do both sexual and asexual reproduction?
Fungi produce spores which are asexual, but if they meet another fungus of the same species, they can also reproduce sexually
What sort of parasites do both sexual and asexual reproduction?
The parasite that causes malaria, reproduces asexually inside the human host and sexually inside the mosquito
This is its normal life cycle.
What is DNA?
DNA is a chemical polymer made up of two strands joined together and coiled into a double helix shape
What is a chromosome?
A chromosome is a molecule of DNA that has been coiled up tightly to make a much shorter and fatter molecule
What is a gene?
A gene is a short section of DNA in a chromosome that codes for a single protein.
The code of the DNA in the gene is for a particular sequence of amino acids.
What is a genome?
The genome is all of the DNA of an organism. For example, the human genome is all of the DNA that every human would have.
Why is the human genome important?
Scientists have studied the human genome and now know what protein every single gene codes for. This will help scientists studying inherited disorders in the future
How can the human genome help with human history?
Scientists have used the genome to map where humans migrated from and to in the past.
What is a nucleotide?
It is the molecule of that DNA is made from.
Every nucleotide contains sugar, phosphate and the base.
There are four different bases, so there are four types of nucleotides.
So what does a single DNA strand look like?
Like half of a ladder
The sugars and phosphate alternate to make the side of the ladder with the bases bonded to the sugar molecule sticking out like the rungs
What are the different bases in a nucleotide?
These bases are called, A. T. G. C.
The base is attached to the sugar molecule in the nucleotide
How do the nucleotides code for proteins?
Three nucleotides in sequence code for one particular amino acid.
The order of bases controls the order of amino acids in a protein chain.
What are the two stages of protein synthesis?
Transcription (which takes place in the nucleus)
and then translation (which takes place in the cytoplasm at the ribosomes)
What happens during transcription?
A copy of the gene is made from a chemical called RNA.
The copy is called messenger RNA or mRNA and it can leave the nucleus and travel through the cytoplasm
What happens during translation?
A ribosome attaches to the start of the mRNA
as the ribosomes move along, small transfer RNA molecules arrive each bringing an amino acid
How are the amino acids placed in the correct order?
So mRNA is the template showing which amino acids needs to be put in the protein.
The sequence of the bases means the correct protein is made.
What happens to the protein when the ribosome reaches the end?
At the end of the mRNA the ribosome releases the protein.
The protein folds off to form a unique shape so that it can do its job
Why do proteins have specific shapes?
Many proteins need to bind to other molecules (e.g. enzymes and hormones) or need to be specific shape so they can do their job (e.g. collagen holds structures together)
What will happen if the order of bases in DNA is incorrect?
This is called a mutation as a result, the wrong amino acid could be put into a protein
Are all mutations harmful?
Many mutations have no effect on the protein made. Some have an effect that isn’t harmful and some can have helpful effects. A few mutations are harmful.
When do mutations happen?
Mutations occur all the time though some conditions can make them more likely. Often function of the protein is not affected. We are unaware of the mutation.
What happens if the mutation causes the protein to be incorrect?
Is the protein is an enzyme or a hormone it may not fit the molecule that it should bind to. If it is a structural protein (eg muscle protein) it may lose strength.
Does all of our DNA code for proteins to be made?
Some parts dont codes for proteins. Instead, they may be responsible for switching genes on and off. These non-coding parts may affect gene expression.
What is an allele?
A different version of a gene.
Different alleles occur because mutations happen.
Mutations change the DNA code and alter the amino acid sequence of a protein.
What is a genotype?
The combination of alleles that an organism has.
For each gene, every organism should have two alleles in their genotype
What is a phenotype?
The appearance of an individual is their phenotype.
It depends on the genotype and/or their environment (you can choose to dye your hair… it’s not in your genotype )
What does expressed mean in genetics?
Expressed means that a characteristic is visible in an individual because the DNA code has been read and the resulting protein is made
What is a dominant allele?
An allele that is always expressed in the phenotype. It is represented by a capital letter. eg B
What is a recessive allele?
An allele that only shows in the phenotype when there is no dominant allele in the genotype. It is represented by lowercase letter eg. b
What does heterozygous mean?
The genotype when an organism has two alleles that are different eg Bb
What does homozygous mean?
The genotype when an organism has two alleles that are the same as each other eg. BB is homozygous dominant and bb is homozygous recessive
Are all characteristics controlled by single genes?
Some characteristics are controlled by single genes eg blood group
Other characteristics are controlled by multiple genes on different chromosomes e.g. Height.
How do we show the probability of a characteristic?
Probability should always be out of one (but often you can turn it into a percentage or a fraction and still get the marks)
What is a punnet squares diagram?
A box shaped diagram that we can use to predict the probability of a particular characteristic being expressed
What is an inherited disorder?
Any disorder that can be passed on from one or both parent. For GCSE, you need to know about polydactyly and cystic fibrosis.
What is polydactyly?
This disorder gives a sufferer extra fingers and/or toes. It is caused by a dominant allele.
What is cystic fibrosis?
This disorder affects the cell membranes of sufferers and causes thick mucus to be produced which affects many parts of the body.
It is caused by a recessive allele.
What is embryo screening?
Treating DNA of an embryo to find out whether it will be a sufferer of a particular disorder. Parents can choose whether to continue the pregnancy
Why do some people think embryo screening is good?
It reduces the number of children born with inherited disorders. This reduces suffering and distress and it also reduces the cost for the NHS as fewer treatments are needed.
Why do some people think embryo screening are bad?
It results in otherwise healthy embryos being destroyed. Some people disagree with this as every embryo is a potentially a life.
How many chromosomes does a normal human have?
Every human body cell has 46 chromosomes arranged as 23 pairs. One of each pair came from each parent during fertilisation.
What are the sex chromosomes?
Pairs 1-22 code for normal characteristics. Pair 23 is the pair that control what gender are the person will be pair 23 are the sex chromosomes
What are the sex chromosomes in a female?
The two sex chromosomes are the same as eachother in females. They r both X , so we say females have XX
Wht ar the sex chromosomes in males?
The two sex chromosomes are different to eachother in males.
They have one X and one Y so we say males have XY
What are the chances of an embryo being a male or a female?
Every embryo has a 0.5 probability or a 50% chance
What is variation?
Any differences in appearance between individuals of the same species in a population.
What causes variation?
Variation in a population is caused by the different genes they have inherited
or the environment they have developed in,
or a combination of genes and environment
How does variation arise?
Variation in DNA is caused by mutations altering the DNA code. Most mutations don’t have any affect on phenotype but a few do
How often do mutations occur?
Mutations are always occuring but most are not noticed as they don’t affect the phenotype of the individual.
How does natural selection work?
If a mutaion gives a new allele, and the new phenotype gives a survival advantage in the environment.
The allele will be passed on more often to the offspring.
What is 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
What does the theory of evolution suggest?
That’s already species have evolved from simple life forms that exists over 3 billion years ago
How do new species form?
If two populations of the same species evolve differently, they will no longer be able to interbreed and produce fertile offspring. We say they are different species.
What is selective breeding?
This is when humans take advantage of natural selection to pick genetic characteristics for the offspring to inherit.
Humans have been doing this for thousands of years
How does selective breeding work?
Pick parents with the desired characteristics and only allow these individuals to breed.
From their offspring pick only the ones with the desired characteristics to breed.
what sort of characteristics do we selectively breed for?
Animals that produce more meat or milk
Domestic dogs that are gentle
Large or unusual flowers
Food crops that are resistant to diseases
How long till selective breeding take?
It can take many generations of picking the individuals to breed before all the offsprings show the desired characteristic
What is the disadvantage of selective breeding?
Individuals who are selectively bred for a long time, can become inbred
inbreeding leads to the individuals who are more likely to get disease or inherited defects
What is genetic engineering?
Scientists can modify the genome of an organism by introducing a gene from another organism to give the desired characteristics. The new organism is G. M.
What do we mean by the term GM?
Genetically modified is the term used to describe any organism that has been genetically engineered, even if only one gene in thousands has been added
What sort of genetic engineering do we do to plants?
Plants have been genetically engineered to produce bigger, better fruit or to be resistant to diseases.
What sort of genetic engineering do we do to bacteria?
Bacterial cells have been genetically engineered to produce useful chemicals such as human insulin to treat diabetes
How are genes transferred from one organism to another?
The gene that is useful is cut out and transferred into the DNA in cells of other organisms
How are the genes cut out?
Enzymes are used to cut the gene from the chromosome. The gene is inserted into a vector such as plasmids or a virus which is then used to put the gene into DNA of new cells.
When would genes be transferred into a different organism?
The transfer has to happen at an early stage of development so that the organism has the gene in all of its cells as it develops
What are the advantages of GM crops?
GM crops have been engineered to be resistant to insect attacks or herbicides
most GM crops have higher yields more crop, is produced per hetacre)
What are the concerns about GM crops and human health?
Some people feel the effects of eating GM crops haven’t been fully explored
What are the concerns about GM crops and the environment?
Some people are concerned that GM crops may start breeding with wildflowers, or may affect insect populations and therefore affect food chains
can GM help people with inherited disorders?
There is an ongoing medical research to see if genetic modification can overcome problems caused by inherited disorders, such as cystic fibrosis. It may be a possibility.
What is cloning?
Making a genetically identical copy of an organism
What are the different types of cloning
Tissue culture and cutting are ways of cloning plants
embryo transplant and adult cell cloning are ways of cloning animals
How does tissue culture work?
small groups of cells are taken from part of a plant and grown into genetically identical new plants. This is done in sterile conditions in a petri dish.
How is the tissue culture useful?
Rare plant species can be grown from a single plant as many new plants can be grown from the cells in a single leaf. It is also useful in commercial horticulture.
How do cuttings work?
A large piece of a plant, including some leaves and stems are cut. This plant will grow new roots from the cut stem. This is an old-fashioned method used by gardeners.
How are cuttings useful?
Many genetically identical new plants can be grown from the parent plant.
In species of plants that will easily grow from cuttings this is a cheap and easy method.
How do embryo transplants work?
Taking an early stage animal embryo and spliting it into several embryos before implanting it into host mothers.
This needs to be done before cells in the embryo specialise .
How are embryo transplants useful?
Cattle can be bred like this. Taking an embryo bred from high quality parents, splitting it an implanting into lower quality mothers will quickly improve a herd .
How does adult cell cloning work?
Putting a body cell nucleus into an unfertilised eggs out (this has had its nucleus removed)
and making it divide to form an embryo that could be implanted into the uterus of a host mother.
How is adult cell cloning useful?
It may be useful in the future to produce organs for transplants, but there are many ethical considerations, and it is still at the research stage
What are the risks of cloning?
The long-term effects on the embryos are not always known. There may be health issues later on in life or health problems may start at a younger age than normal.
Why do some people have ethical objections to some cloning
Some embryos are destroyed, and this may be considered unethical. Some people are often concerned about where cloning research will lead to in the future.
What is the theory of evolution by natural selection?
That there is a wide range of variation within a species
and some individuals will have characteristics that make them more likely to breed successfully and pass on alleles
Who propose the theory of evolution and when?
Charles Darwin published his idea for the theory in 1859
What research led to the proposal of the theory of evolution?
A round the world boat expedition, years of experimentation and discussion linked to knowledge of geology and fossil finds
Why was the theory of evolution only gradually accepted?
The theory challenges the idea that God made all living things. There was insufficient evidence of the time to convince other scientists, and genetic inheritance was not known until 50 years later.
Who else propose the theories of evolution?
Jean Baptiste Lamarck’s theory was that changes happening during an organisms lifetime will be passed on to their offspring. We know this is virtually impossible.
What is the best speciation?
New species arising from previous species
Who was Alfred Russel Wallace?
A scientist to also developed the theory of evolution by natural selection independently of Darwin
Did Darwin and Wallace work together at all?
Yes, after separately, coming up with the same theory, they worked together and published a jointly written book in 1858, inspiring Darwin to publish his book in 1859
What research is Wallace best known for?
He worked worldwide, gathering evidence for evolutionary theory. He is best known for his work on warning colouration in animals and his theory of speciation.
How does the theory of speciation link to natural selection?
If a population is isolated from other populations over many generations of natural selection, they may become so different, that the different populations no longer interbreed and have become the separate species
What does the theory of speciation assume at the start?
That there is genetic variation within the population. Also that there are environmental conditions that benefit adaptations of some individuals and not others
Is there more evidence for speciation now?
Yes, scientists have seen specialisation occur over a long time with many species. Specialisation is also seen in lab grown bacterial populations and this is much quicker.
Which scientist is described as the father of modern genetics
Gregor Mendel an Austrian monk
Why were mendels discovery is not widely accepted at the time
Scientists did not understand the mechanism of inheritance.
chromosomes had not yet been identified due to poor microscope lenses,
and DNA was not discovered
When did Mendel carry out his breeding experiments?
In the mid 19th century
What does mendel carry out his breeding experiments on?
He worked with a variety of plant species, most famously pea plants
He investigated the flower colour, height, pea colour and whether the peas were wrinkled or round
What did Mendel call genes before they were discovered?
Mendel realised that something was being passed on from parents to offspring. He called them units because he didn’t know what they were.
When did chromosomes first get identified?
in the late 19th century, scientists saw chromosomes during cell division and observed their behaviour at different stages of mitosis
When did scientists make links with mendels discoveries?
In the early 20th century, scientist realise that the behaviour of chromosomes and Mendells units behaved and similar ways. The units were now called genes.
When was the structure of DNA determined?
In the mid 20th century, the structure of DNA was determined by Watson, crick and Franklin and finally the mechanism for how genes function was worked out
What evidence is there that evolution occurs?
Fossils have been found that support the theory of evolution
Also antibiotic resistance has shown that bacteria has evolved. Plus we now know how genes works.
Is evolutionary theory by natural selection now accepted?
The theory is widely accepted worldwide as the range of evidence is huge
What are fossils?
The remains of organisms that have lived millions of years ago they are found in rocks
How do fossils form?
From parts that have not decayed,
When parts are replaced by minerals as they decay
Has chases such as footprints and borrows
What sort of fossils occur?
Apart from the traces (borrows, footprints leafprints etc) fossils are hard parts of animals that have turned into rock
Skeletons, shells, claws are most likely to fossilise
Why can’t we find fossils for early life forms?
Soft body parts don’t fossilise as these parts decay
Early life forms, we are mostly just soft bodied
Bacteria have no hard parts to fossilise, so we can’t find evidence for them
Why can’t scientists prove how life on Earth began
As scientists are sure that early life started with fossils, but there is no physical evidence to support this theory, so it can’t be proved
What can scientists find out from fossil evidence?
Scientists can see how much or how little life on earth has changed over time
Some deep ocean species have changed the least e.g. horseshoe crab and shark
What is an evolutionary tree?
A diagram that shows how different species are linked over evolutionary time
Relationships and common ancestors can be seen in the evolutionary trees
What does extinction mean?
When every individual of a species on earth is dead. we say that species has become extinct
Why do species become extinct?
If Species cannot survive environmental changes then every member of our species will die
Do humans cause all extinctions?
No, many species were extinct before humans existed but in modern times we have become responsible for many species becoming extinct.
What do humans do that cause of species to become extinct?
Humans destroy habitats reduce food availability, or hunt and kill other species.
All of these can cause a species to become endangered or extinct.
Why do bacteria evolve more quickly than other species
Bacteria reproduce very quickly Some species can reproduce every 20 minutes so they can get to many generations in a few weeks.
What do we mean by resistant bacteria?
Bacterial pathogen strains that are not easily killed by antibiotics and so are difficult to treat
How do bacteria become resistant?
Mutations occur to the DNA and bacteria. This produces new strains and some of these are resistant to particular antibiotics. They survive, reproduce and increase in number.
What is MRSA?
A bacterial strain that is resistant to many antibiotics and causes several deaths each year
What is the worst problem with resistant bacteria?
Some bacterial strains can evolve to become resistant to several antibiotics. They may be no effective treatment for these strains at all.
How do doctors help reduce the risk of bacterial resistance?
Doctors should not prescribe antibiotics for nonserious bacterial infections or for viral infections
How can patients help to reduce the risk of bacterial resistance
Patients given antibiotics should complete the whole course of antibiotics so that all bacteria are killed and not survive to mutate and form resistant strains
How can the agriculture industry help reduce the risk of resistance?
Antibiotics used to be given to farm animals regularly in their feed and this should be restricted to only vets treating an emergency
Why can’t we just develop new antibiotics for the resistant strains?
Developing new antibiotics is very expensive and slow
Drug development can’t keep pace with the speed at which new resistant strains are emerging
What is classification?
Placing species of living things into nonoverlapping groups, depending on the structure and characteristics
The system for classification was developed by Carl Linnaeous.
What groupings did Linneaus develop?
Kingdom, phylum, class, order, family, genus and species.
Kingstons are the largest groups and species are the smallest groups
How are organisms named in Linneaus’ system?
Binomial system namings, where each organism is given two names, is genus name and it’s species name.
eg humans are homo sapians (genus - humans and species - sapiens)
Has classification changed since Linneaus developed it?
Yes, better biological evidence has seen species move into more appropriate groups.
Also new models of classification have been proposed.
What sort of evidence is needed to make changes to classification?
Better microscope evidence of internal cell structures, and better understanding of biochemical processes within cells and organisms
Who is Carl Woese?
A scientist who proposed a new “three domain system” based on evidence from chemical analysis
What are the three domains?
-Archaea
-True bacteria
-Eukaryota (protists, fungi, plants and animals)
What are Archaea?
Primitive bacteria, usually living in extreme environments (they have not evolved like true bacteria due to the extreme conditions they need to be adapted to survive).
How can evolutionary trees be used in classification?.
Relationships between living organisms and extinct organisms can be seen from a tree and link with the past
