Inheritance, Variation and Evolution Flashcards
Asexual reproduction involves…[4]
- Only 1 parent
- No fusion of Gametes (genetics) = no genetic variation
- Clones
- Mitosis
Sexual reproduction Involves… [4]
- Two parents
- Fusion of gametes (genetics)
- Variation in offspring
- Meiosis
Haploid
Single set of unpaired chromosomes
Diploid
Two complete pairs of chromosome: one from each parent
How do Strawberry plants/spider plants asexually reproduce? [2]
- Strawberry and spider plants reproduce by mitosis
- New plants form on the end of stems called runners
- New plants will form (even if destroyed by frost, eaten or fail to be pollinated)
How do daffodils asexually reproduce? [2]
They produce lots of smaller bulbs which can grow into new plants
How do fungi asexually reproduce?
Using spores= produced by mitosis
-genetically identical to parents
Where do Malaria Protists asexually reproduce?
When they are in the human host
Describe the process of Meiosis [6]
- Diploid cell present ( two pairs)
- Each chromosome replicates
- Part and move to opposite poles
- Cell divides for first time
- Copies now separate original chromosome
- Four haploid cells present, each with half the number of chromosomes as parent cell
Pollination [2]
plant gametes =egg and pollen
- Pollen is transferred from one plant to another
- This pollen fuses with an egg to form a seed
- introduces varation
How does the Malaria parasite reproduce? [6]
- Infected mosquito releases parasite via blood stream
- Travels to the liver=> multiplies due to asexual reproduction
- Enters RBC=> develops into female and male gametes
- Gametes transferred to new mosquito
- New parasite infects new human
- Introduces variation
What are the advantages of Asexual reproduction? [3]
- Time and energy efficient
- Faster than sexual reproduction
- Many identical offspring produced=> make most out of good conditions
What are the advantages of Sexual reproduction? [3]
- Variation
- => protects some from environmental changes
- Selective breeding
Genome
The entire DNA sequence of an organism
What benefits can be gained from the study of the human genome? [5]
1) Improved testing for genetic disorder- to discover if people are carrying a faulty allele
2) New ways of finding genes that may increase the risk of certain diseases e.g. Alzheimer’s, heart disease
3) New treatments and cures for disorders e.g. Gene therapy - try to replace or mend faulty genes that cause the disorder
4) personalised medicines- target diseases more effectively, with fewer side effects
5) New ways of looking at changes in the genome over time- e.g. How humans have evolved, evolutionary relationships between different species
Describe the structure of DNA [5]
- DNA = polymer => made up of repeating nucleotide
- A nucleotide = phosphate, sugar and a base
- 2 strands coil and twist together to form a Double helix
- DNA is made up of alternating sugar and phosphate sections that make up the backbone of the molecule
- DNA strands are linked together at regular intervals by bases held by hydrogen bonds
- There are 4 bases ACTG
- A=T, C=G form complementary base pairs
What are the 4 bases?
A,C,G, and T
C links to…
G
A links to
T
How does DNA code for proteins? [4]
- DNA contains bases
- Order of the three bases
- Code for specific amino acids
- Which fold to form a specific protein
What are the two stages to Protein Synthesis?
- Transcription
2. Translation
Describe Transcription [6]
- Takes place inside nucleas
- Weak hydrogen bonds brocken between complementary bases
- DNA unzips
- Two strands separate
- Forming a template strand called mRNA
- mRNA small enough to leave nucleas
Describe Translation [6]
- TEMPLATE STRAND (mRNA) attached to a ribosome in the cytoplasm
- Cytoplasm contains carrier molecules (tRNA), attached to specific amino acids
- Ribosomes moves along the mRNA strand
- Carrier molecule keep adding on amino acids
- Amino acids forms a chain called polypeptide
- Polypeptide twist and folds to form a protein
What does Mutation mean? [4]
- Change in sequence of bases
- Different template
- Different sequence of amino acids
- Different protein shape
What are the possible positive effects of mutation? [2]
- More efficient enzymes
OR - Stronger Structural protein
What are the possible negative effects of mutation? [2]
- Active site may no longer fit into substrate
OR - Structural protein may lose its strength
What are the functions of proteins? [4]
- Structural (builds Cells and tissue)
- Hormones -chemical messengers
- Carrier molecules, e.g. haemoglobin
- Enzymes- speed up reactions
Gene expression
- Gene codes for a protein- that has been synthesised
- MOST OF OUR DNA DOES NOT ACTUALLY CODE FOR PROTEIN. This is called non-coding DNA
- Non-coding DNA are involved in switching genes on or off.
- Switching genes on and off control which proteins are made
- If mutations occur in the non-coding DNA- a gene MAY be turned on when it should be turned off. Which will produce protein, which is not meant to be produced at the time.
- Variation in the non-coding of the DNA affect how our genes are expressed- effects phenotype
Genotype
Combination of allele for a characteristic
Phenotype
Characteristic expressed
Homozygous
2 alleles that are the same
Heterozygous
2 alleles that are different
Gene
A section of DNA that codes for a particular protein
Allele
One form of a gene
Dominant allele
Expressed even when other alleles are present
Recessive Allele
Not expressed when dominant allele is present
What is polydactyl caused by and what are its symptoms? [2]
- Cause by dominant allele
2. Extra fingers toes and thumbs
What is Cystic fibrosis caused by and what are its symptoms? [4]
- Caused by recessive allele
- Produces thick sticky mucus in cell membranes
- Clog airways=> infection and breathing difficulty
- Mucus builds in pancreas=> prevents release of enzyme effecting digestion
Describe Gregor Mendel’s Pea experiment [3]
- He bred plants with green pods and plants with yellow pods
- The first generation showed only green pods produced, showing green was dominant and yellow recessive
- Second generation, there were 3 times as many green as yellow ( dominant and recessive)
What conclusions could be make from Mendel’s work? [2]
- Some characteristics were dominant and some recessive
2. Plants passed on inheriting factors
Why wasn’t the importance of Mendel’s work during his lifetime recognise? [2]
- He was a monk, not a scientist at a university
- He did not publish in a well known book or journal
- genes not discovered
Where does an individual receive alleles from?
One in each pair from the mother and one from the father
What was the names of the two groups of scientists involved in DNA discovery?
- Maurice Wilkins and Rosalind Franklin
2. Crick and Watson
What was the role of Maurice Wilkins and Rosalind Franklin in the discovery of DNA? [2]
- Took an x-ray photography=> show it had a regular structure
- Wilkins thought it was a helix
What was the role of Crick and Watson in the discovery of DNA? [4]
- Tried to build a 3D model to show how it works
- 1953: Wilkins showed the pair Franklins image
- They thought it was a double helix, with bases like rungs on a ladder
- 1962, Wilkins, Crick and Watson Nobel prizes, but Franklin died
Variation
Difference in characteristics of individuals in a population
Describe the process of selective breeding [4]
- Parents with desired characteristics chosen
- Bred to produce offspring
- offspring with desired characteristics are selected and bred
- Repeated over generations
Why may selective breeding be used? [4]
- Disease resistance in food crops.
- Animals which produce more meat or milk.
- Domestic dogs with a gentle nature.
- Large or unusual flowers.
What are the problems with selective breeding? [3]
- Reduces number of alleles (gene pool)
- Reduces variation (=> climate change/ disease issue)
- Inbreeding (recessive disorder passed= more likely to be susceptible to diseases )
Genetic Engineering
- Process of taking genes from one organism
- And putting it into the cells of another
- So the cells include characteristics of the new gene
Describe the process of Genetic Engineering [3]
- Cut out genes using cutting enzymes
- gene inserted into a vector, e.g. bacterial plasmid
- Vector is used to insert gene into required cell
in animal= placed into embryo/egg=> divide and grows by mitosis and develops new characteristics
in plants= placed into meristems => divides by mitosis and develops new characteristics
What happens when genes are transferred to cell at an early stage of their development?
As the organism grows, it develops with the new desired characteristics from the other organism
How can Insulin be genetically engineered?
- Enzyme used to cut insulin gene out of DNA from human cell
- Plasmid taken out of bacterium and split using enzyme
- Insulin gene inserted into plasmid by another enzyme
- This is taken up by bacterium
- Bacterium multiplies many times
- Insulin gene is switched on and harvested
What can plants be genetically engineered to do? [2]
- Be resistant to disease, insect or herbicide attack
2. Produce bigger, better fruits
How can clones be produced using adult cells? [6]
- Remove nucleus from body cell with desired characteristics
- Remove and discard egg nucleus
- Insert body cell nucleus into empty egg cell
- Stimulate division using electric shock
- Allow development of embryo
- Insert into uterus of host mother
=identical clone=>not biologically related to host mothers
Describe how Embryo Transplant works?
- Divide an embryo into several individual cells
- Each cell grows into an identical embryo in the lab
- Transfer embryo into host mothers (given hormones for prep before pregnancy)
- Identical cloned babies born (not biologically related to host mothers
How are new species formed? [6]
- Species become separated or isolated due to geographical barrier
- Genetic variation (mutation)
- Different environmental conditions mean some adapt and survive
- Natural selection occurred
- Favourable genes were passed on in each population
- Two types become so different that they cannot interbreed successfully to produce fertile offspring
What was Lamarck’s theory? [2]
- His idea was that every animals evolved from primitive worms
- Change was caused by inheritance of acquired characteristics
What were the problem with Lamarck theories? [3]
- No evidence
- People didn’t like to think they descended from worms
- Changes were not passed on (counteracting evidence)
Describe the process of natural selection [5]
- Variation in population
- Variation is caused by mutation
- More food means they are more likely to survive
- They breed and reproduce
- These favourable genes are passed to offspring
Species
Organisms that can breed together successfully produce a fertile offspring
Fossils
Dead ‘remains’ of organisms (animals or plants) from millions of years ago
What evidence do fossils provide? [3]
- Fossils show changes over time
- Fossils have similar features to present-day species
- Supports theory of evolution
How are fossils formed? [3]
- Hard parts of animals do not decay easily
- Conditions needed for decay are absent (soft tissues are preserved)
- Preserved traces of organisms, e.g. footprints, burrows and traces
new: Fossil is covered in sediment or mud BONES DO NOT DECAY Minerals enter the bone FORMING fossils
What may extinction be caused by?
- Changes to environment over geological time
- New predators
- New diseases/ mutations
- New more successful competitors
- Through cyclical nature of speciation
- a single catastrophic event
How are antibiotic-resistant strains of bacteria formed?
- Non resistant bacteria exist
- Bacteria multiply by the billions=> some mutate
- Some mutations make bacterium drug resistant=> only drug resistant bacteria survive
- Drug resistant bacteria multiply and thrive
What observations did Dickens make? [4]
- Organisms often produce large number of offspring
- Populations usually stay about the same size
- Organisms are all slightly different- variation
- Characteristics can be inherited
Why are there gaps in the fossil record? [4]
- Soft tissue decay and do not form fossils
- Hard parts destroyed by geological activity
- Lack of fossils- lack of evidence
- Many buried deep in the earth and have not been found yet
How did Linnaeus classify living things?
Kingdom=> phylum=> class=> order=> family=> genus=> species
naming species
first part = genus
second part= species
Classification
Living things are grouped together based on their similarities
Why were new models of classification proposed? [2]
- Microscopes improved, so scientists learnt more about cells
- Biochemical processes became better understood
How are organisms organised under Car Woese’s 3 domain system?
- Archea (primitive bacteria)
- Bacteria (true bacteria and bacteria that can photosynthesise)
3 Eukaryota (protists, fungi, plants and animal= nucleus enclosed with DNA)
Why do new species often form on islands?
because they are isolated from populations on other islands
Evolutionary trees
Method used by scientists to show how they think species are related
How does Embryo screening work?
- Egg fertilised with sperm in a dish
- Embryos tested to see whether they carry the allele for disorder
- Embryo that do not contain faulty gene placed into the women womb to develop into a baby
What is the risk of embryo screening?
Risk of miscarriage
Genetically modified rice
adv:
Rice contains beta carotene which makes vitamin A
=> Vitamin A will reduce blindness and death
disadv:
- Cross breed with wild rice and contaminate wild rice DNA
- Beta carotene may not be high enough to make a difference
- Eating GM organism might harm people.
- Some are made so they do NOT produce fertile seed – meaning farmers have to buy new seed each year. (EXPENSIVE)
Human insulin genetically modified (GM) by bacteria
adv:
1. used by vegans
2. Not affected by animal disease
3. Made in large quantities
4. Cheap
disadv:
1. Bacteria produce insulin which is slightly different, may not work on every one
Herbicide-resistant
adv:
- Reduces amount of crop spraying => don’t have to buy herbicides
- less use of ‘chemical’ insecticides/less pollution
- Reduce labour costs
- increases yield = more profit
disadv:
- Toxin might affect other organisms that feed on plant eg useful insects
- Could mutate to form a human toxin
- Damage to food chain
- Reduced biodiversity
- Can PRODUCE herbicide-resistant weeds as cross-pollination with wild plants takes place
advantages of genetic modification
- Genetic modification is a faster and more efficient way of getting the same results as selective breeding.
- improves food value
- Improve crop yields or crop quality, which is important in developing countries. => may help reduce hunger around the world.
disadvantages of genetic modification
- GM crop seeds are often infertile= new seeds need to be purchased = more expensive and so people in developing countries cannot afford them.
- Effect on human health unknown
=> Toxins may effect food chain - Some people believe it is not ethical to interfere with nature in this way.
method 1 cutting
- Parent plant is cut off, its lower leaves are removed, and the stem is planted in damp compost
- Plant hormones- encourage new roots to develop.
- Cutting is covered in a clear plastic bag to keep it moist and warm.
- After a few weeks, new roots develop and a new plant is produced.
tissue culture
- Remove a small tissue sample from the tip of the parent plant
- Place tissue sample in the STERALISED AGAR. Must use aseptic technique to prevent contamination
- Agar contains nutrients and hormone auxin
- Plant cells DIVIDE to form a big mass of tissue called a callus
- Then use different hormones and condition- stimulate growth of roots and stem
- Each cell forms a new plant
- Transfer into compost where IDENTICAL CLONES GROW
advantages of tissue culture
- Large quantities of IDENTICAL plants are produced
- Quick and easy process
- Preserve rare plant species
- Reliable and safe method
- Produce diseases resistance crops
disadvantages of tissue culture
expensive
advantages of cloning
- can quickly make copies with useful characteristics
- extinct and endangered species can be repopulated
- profit and yield of selected animal increases
disadvantages of cloning
- reduces gene pool
- ethical - discarded embryos
- Reduces variety in a population, less able to survive if there is a change in environment
5 kingdoms
plantae fungi Animalia Protista prokaryotae
in six kingdoms
prokaryotae= bacteria and archaea
