Topic 6 - Inheritance, variation and evolution Flashcards
What base matches with A?
T
What base matches with C?
G
How are proteins made in the body?
- The DNA copies itself
- Then it undergoes transcription to synthesis mRNA
- The mRNA passes into the cytoplasm where it enters a ribosome.
- It then undergoes translation to make amino acids.
- These amino acids are chained together to form polypeptides, which then form proteins.
What is a codon?
A codon the triple code, which is read to form amino acids.
What is DNA?
The molecule in cells, that stores genetic information.
What is a gene?
A short section of DNA, which controls the development of a characteristic and contains instructions to make proteins
How many pairs of chromosomes in humans?
23 pairs
How many genes in a human?
25,000
How many cells in a human?
30 trillion
30,000,000,000,000
What are the 4 DNA bases?
A,T,C,G
What is a mutation?
A mutation is a random change in an organisms DNA, they can sometimes be inherited
What causes mutations?
Mutagens, which are agents such as radiation or chemical substances.
What are nucleotides made of?
Deoxyribosugar + phosphate + base
What are 2 things which cause mutations?
1.Radiation
2.chemicals
What is an insertion mutation?
Insertion is when an extra base is added to a string of DNA
What is a deletion mutation?
When a base is removed from a string of DNA
What is a substitution mutation?
When a base is changed in a string of DNA
What is sexual reproduction?
When 2 gametes combine at fertilisation to produce a generically different individual
What is asexual reproduction?
When organisms reproduce by producing a copy of themselves, the offspring is genetically identical
What are the advantages of sexual reproduction?
- All offspring are different
- Organisms are more protected
- Allows for better evolution
What are the disadvantages of sexual reproduction?
- Needs two parents
- Time consuming
- More energy needed
What are the advantages of asexual reproduction?
- Only one parent needed
- quick
- offspring are clones
- less energy needed
What are the disadvantages of asexual reproduction?
1.No variation
What is mitosis?
When cells divide to produce identical copies,
What is meiosis?
When cells divide, but the cells produced are unique and half the number of chromosomes.
What are the steps of meiosis?
- The DNA replicates
- The cell then splits into 2 daughter nuclei, both with 46 chromosomes each
- Those cells then split again into 2 other cells.
- These cells only have 23 chromosomes each, and are genetically unique.
Which gametes decide a baby’s gender?
The sperm, because it can have X and Y chromosomes, eggs can’t.
How many genes are in Y chromosomes?
78
How many genes are in X chromosomes?
900-1200
What is an Allele?
An alternate version of a gene
What is a phenotype?
The characteristics you have
What is a genoptype?
What alleles you have
What does homozygous mean?
Where an organism has two alleles for a particular gene that are the same.
What does heterozygous mean?
Where an organism has two alleles for a particular gene that are different.
What are chromosomes?
Long molecules of DNA found in he nucleus, carrying genes
What is DNA?
The molecule in cells that stores genetic info
What is a gene?
A shor section of DNA, found in a chromosome, which contains the instructions needed to make proteins and controls the development of a characteristic
What is a zygote?
When a sperm and egg have just fertilised
What is cystic fibrosis?
An inherited disorder that creates a thick, sticky mucus- It affects a number of organs, but especially the lungs and pancreas - it is life limiting and incurable
Is cystic fibrosis recessive or dominant?
Recessive
What is polydactyly
Rare but serious defect which causes child to grow extra fingers
Is polydactyly recessive or dominant
Dominant
What is sickle cell anaemia?
- causes oddly shaped red blood cells
- These die quickly and block blood vessels
- Can lead to a variety of problems and can be painful
Is sickle cell anamia recessive or dominant?
recessive
What is PGD(pre-implantation genetic diagnosis)?
Before an embryo is implanted in IVF, a cell is removed from each embryo and its genes are analysed to see if it will be healthy. This means faulty ones can be destroyed/
What is CVS(Chorionic villus sampling)?
carried out between 10-13 weeks of pregnancy- it involves taking a sample of cells from a part of the placenta and analysing its genes. This part of the placenta develops from the same original cells- so they can be scanned for genetic disorders. If there is an issue the embryo can be terminated.
What are arguments for genetic screening?
- Gives parents the choice
- Helps to stop certains disorders
- Preventing disorders saves money in treatment later
- Most embryos in IVF are destroyed anyways - PGD just picks the best
What are arguments agains genetic screening?
- CVS can cause a miscarriage
- Designer babies are really dodgy
- Increase in prejudice between rich twatty designer twat babies and regular plebian monks
- Expensive at first
- Destroying life
What did Mendel do in his experiment?
1.He bred a tall pea plant with a short one and got all tall plants
2.He then bred the 4 offspring and got 3 tall and 1 short
What did Mendel discover?
Mendel had shown that characteristics were inherited in hereditary units, passed on from each parent. The ratio between tall and short plants, showed that the tall unit was dominant
What conclusions did Mendel make?
- Characteristics in plants are determined by hereditary units
- Hereditary units are passed on to offspring unchanged from both parents - 1 unit from each
- Hereditary units can be dominant or recessive
Why didn’t people understand Mendel’s work at first?
- Chromosomes were not discovered until the late 1800s
- In the early 20th century, scientists realised that the chromosomes behaved similarly to Mendel’s units - so scientists proposed that units were found in chromosomes - units were renamed to genes
- In 1953 - the structure of DNA was determined
How does genetic variation within species occur?
- genes from the mother and father mix and creates a genetically different offspring.
What are the 2 types of variation?
- genetic
- environemental
What does the theory of evolution state?
All of today’s species have evolved from simple life forms that first started to develop over 3 billion years ago
What is survival of the fittest?
Only the organisms with the most suitable characteristics would survive and reproduce
Explain natural selection
- Different organisms have different characteristics due to random mutations in DNA
- When the environment changes, the ones with more suited characteristics survive and pass on their genes
- The organisms less suited are more likely to die off and not reproduce
- Over time the beneficial characteristics become more common in the population and the species evolves.
What does speciation mean?
When a new species is formed, and the members of the new species cannont breed with members of the old species to produce fertile offspring
What are some things which can cause extinction?
- Environment changes too fast
- New predator kills them all
- New disease kells them all
- New competions
- Catastrophic event
Why was Darwin’s discovery controversial?
- many people were religious and thought it went against religion
- Darwin couldn’t explain how the useful characteristics appeared or were passed on
- There wasn’t much evidence to convince other scientists.
What did Jean-Baptiste Lamarck say that differed to Darwin
Lamarck said that changes an organisms aquired during its life will also be passed on
What is selective breeding?
When humans artificially select the plants/ animals that are going to breed so that the genes for a particular characteristic remains in the population
Why do we selectively breed organisms?
To make organisms develop features thaty are useful or attractive:
1. produce more milk/meat
2. disease resistance in crops
3. Gentle/ cute pets
4. decorative plants with mahoosive flowers
What is the process of selective breeding?
- Select the organisms with the desired characteristics
- breed them
- Select the brest of the offspring and breed them
- Continue this precess over several generations.
What is a gene pool?
- The number of different alleles in a populaton
What is the drawback of selective breeding?
1.Reduces the gene pool due to inbreeding
2.This causes health problems as there is a higher chance of inheriting genetic defects
3.If a new disease appears, it can be very dangerous
What is genetic engineering?
Transfering a gene responsible for a desirable characteristic from one organisms’s genome to another one’s
How is genetic engineering done?
- A useful gene is isolated from one organism’s genome using enzymes, and is inserted into a vector
- The vector is usually a virus or a bacterial plasmid depending on the organisms the gene is being transferred to
- When the vector is introduced to the target organism, the useful gene is inserted into its cells
What is genetic engineering used for?
- Bacteria have been modified to produce human insulin
- GM crops have improved size and quality of fruit, and were made resistant to desiease, insects and herbicides
- Sheep have been engineered to produce substances like drugs in their milk
- It can be used to treat inherited diseases too
Why is genetic engineering controversial?
There are worries about the long term effects of genetic engineering
What are the pros of GM crops?
1.increased yeild
2.Can be made to have more nutrients
3.Already being used without problems
What are the cons of GM crops?
- Affects the number of wildflowers and insects, lowering biodiversity
- Not everyone is convinced it is safe
- Tranplanted genes may get into the natural environement
How are plants cloned from a tissue culture?
- A few plant cells are put into a growth medium with hormones - these grow into new plants
What are the benefits and uses of cloning plants in a tissue culture?
- Used by scientists to preserve rare plants
- Used by plant nurseries to produce lots of stock quickly
- The tissue culture requires very little space and can be used all year
How are plants cloned using cuttings?
- A cutting is taken from parent plants
- This is then planted
What are the benefits to cuttings?
1.quick
2.cheap
3.simple
How are animal clones made?
Embryo transplants
1. Sperm cells are taken from a male and egg cells are taken from a female
2. The sperm is used to artificailly fertilise an egg cell
3. The embryo that forms is split many times to form clones
4. These cloned embryos can then be implanted into many other organisms to create clones
How is adult cell cloning done?
- An unfertilised egg cell has its nucleus removed.
- The nucleus from an adult body cell is then inserted into the empty egg cell
- The egg cell is then stimlulated by an electric shock which makes it divide into an embryo
- This develops into a gentically identical copy of the original adult body cell
What are some issues around cloning?
- Reduced gene pool
- Cloned creatures are less healthy
- human cloning can be unethical - playing God
What are pros to cloning?
- Study of animal clones can lead togreater understanding of the development of the embryo and of ageing/ age related disorders
- Cloning can be used to help preserve endangered species
What are 3 ways fossils form?
- Gradual replacement by minerals
- Casts and impressions
- Preservation in places of no decay
How do ofssils form from gradual replacment by minerals?
- Teeth, shells, bones don’t decay easily
- So they’re replaced by minerals over time as they decay to form a rock like susbtance - a fossil
How do fossils form from casts and impressions?
- An organism is buried in a soft material
- The soft material hardens and the organisms decay, leaving a cast of itself
- Things like burrows, roots and footprints can leave impressions and casts
How do fossils form from preservation?
- In amber and tar pits there’s no O2 or moisture so decay microbes can’t survive
- In glaciers it;s too cold for the decay microbed to work
- Peat bogs are too acidic for decay microbes
Why isn’t there many fossils from the beginning of life?
- Many early lifeforms were soft-bodied, so it decayed quickly and fully
- Fossils that did form may have been destroyed by geological activity
What can cause speciation to occur?
Isolation - where populations of species are separated by a physical barrier, the environment will be different on each side, so the organisms evolve separately, creating a new species
What did Alfred Russel Wallace do?
- He independently came up with the idea of natural selection and published his work with Darwin in 1858
- He worked on the idea of speciation
What is MRSA?
A superbug - an antibiotic resistant bacteria which is especially common in hospitals and can be fatal if it enters the blood stream
What are ways we can reduce the risk of antibiotic resistance?
- Take the full course
- only use for more serious bacterial infections - not viral ones
What are the steps to the Linnaean system
- Kingdom
- Phylum
- class
- Order
- Family
- Genus
- Species
What are the 3 domains?
- Archaea - primitive bacteria, they are extremophiles
- Bacteria - contains true bacteria
- Eukaryota - includes fungi, plants, animals and protists
What is the binomial system?
- every species is named with 2 parts
- The first part is the genus the organisms belongs to
- The second part refers to the specific species
