Topic 6: Inheritance and Response Flashcards
What are the differences between aesexual and sexual reproduction?
Sexual:
-Two parents
- meiosis and Mitosis
- gametes fuse
- genetic material is mixed
- variation in offspring
Aesexual:
- one parent
- mitosis only
- no mixing of genetic material
- offspring are identical (clones)
What are the advantages of sexual reproduction?
- produces variation in the offspring
- if the environment changes, variation gives a survival advantage
- can colonise new areas by seed dispersal
What are the advantages of aesexual reproduction?
- only one parent is needed
- more energy efficient as there is no need to find a mate
- faster than sexual reproduction
- many identical offspring can be produced when conditions are favourable
What are the disadvantages of sexual reproduction?
- more slower than sexual reproduction
- more energy used to find a mate as 2 parents are needed
What are the disadvantages of aesexual reproduction?
- it does not lead to variation in a population
- the species may only be suited to one habitat
- disease may affect all the individuals in a population
Define fertilisation
The point where two gametes meet
Define gamete
Cells with a single set of chromosomes e.g. eggs and sperm
Define sexual reproduction
Reproduction that involves making unique individuals
Define zygote
Cell formed by the fusion of two gametes
Define diploid and haploid
Diploid - full set of chromosomes
Haploid - half a set of chromosomes
Describe the process during meiosis
- cell grows, increases the number of subcellular structures, DNA replicates
- the chromosomes pairs line up in the centre of the cell
- (1st division) fibres pull copies of chromosomes apart to opposite sides of the cell, the nucleus divides
- (2nd division) the chromosomes line up again in the centre of the cell
- the arms of the chromosomes are pulled apart, nucleus divides
- 4 gametes are produced - each genetically different
Differences between mitosis and meiosis:
Where in the body does it take place?
Mitosis - all body cells
Meiosis - reproductive organs
Differences between mitosis and meiosis:
Number of chromosomes in daughter cells compared to original cell
Mitosis - 46: diploid - full set
Meiosis - 23: haploid - half a set
Differences between mitosis and meiosis:
How many divisions?
Mitosis - 1 division
Meiosis - 2 divisions
Differences between mitosis and meiosis:
How many cells at the end?
Mitosis - 2 identical daughter cells
Meiosis - 4 gametes - genetically different
Differences between mitosis and meiosis:
Is there variation in the daughter cells?
Mitsos - no, produces identical daughter cells (clones)
Meiosis - yes, cells are different to each other and the parent cell
What is a genome?
The genome is all the genetic material of an organism
What is the structure of DNA?
a double helix
a polymer made up of many repeating units
There are 2 strands of DNA
What is a gene?
A section of DNA which codes for a sequence of amino acids
How has the understanding of genomes helped?
- can identify genes that are linked with different diseases
- understanding and treatment of inherited disorders
- understand human migration and evolution
Describe what happens during protein synthesis
- amino acids join together to form a protein molecule
- proteins are synthesised on ribosomes
- carrier molecules bring specific amino acids to add the graving protein chain in the correct order
- when the protein chain is complete it folds up to form a unique shape
- the newly-formed proteins include: enzymes, hormones, forming structures in the body (e.g. collagen)
What is the triplet code?
3 bases code for 1 amino acid
What are the four bases of DNA and how do they pair up?
A always pairs with T
C always pairs up with G
What is a nucleotide made up of?
Phosphate
Sugar
Base (A + T or C+G)
Where is mRNA made and what does it do?
mRNA (the template) is made in the nucleus and is small enough to leave and go to the cytoplasm where it binds to a ribosome
Describe how a protein is formed
- a template is made in the nucleus
- the template then leaves the nucleus
- the template then binds to a ribosome
- the carrier molecules carry specific amino acids to the template (3 bases code for 1 amino acid)
- the carrier molecules attach to the template in order given by DNA
- the amino acids join together to form a protein
- (the complete amino acid chain will fold to form a protease)
What does insertion mutation affect?
It affects all the triplet codes which are read after it. There may be many changes in the amino acid sequence
What does deletion mutations affect?
It affects all the triplet codes after it. If the sequence is different, the 3D shape of the protein will be different and it may have a different function
What does substitution mutations affect?
- very little affect
- it only affects one triplet
- this could still result in a protein with the same 3D shape or very similar
What is an allele?
Each different version of a gene e.g. eye colour
What is a dominant allele?
The gene that is expressed when only one allele is present
What is a recessive allele?
This gene needs both alleles present to be expressed
What do we mean by the term homozygous?
The same type of alleles are present e.g. TT or tt
What do we mean by the term heterozygous?
Alleles in a homologous pair are different e.g. Tt
What is a phenotype?
All the observable characteristics of an organism
What is a genotype?
The full set of genes of an organism e.g. TT, TT or Tt
What is an inherited disorder?
a condition that arises when an individual inherits certain faulty genes or alleles from their parents
What is cystic fibrosis?
An inherited disorder of cell membranes that mainly affects the lungs and the digestive system
How does cystic fibrosis occur?
The lungs or the digestive system becomes clogged with lots of thick, sticky mucus as too much is produced
What did Mendel discover in the mid 19th century?
Through breeding experiments on plants, Mendel observed ‘units’ of inheritance being passed on to descendants
Mendel’s work in the late 19th century
The behaviour of chromosomes during cell division was first observed
Mendel’s work in the early 20th century
Chromosomes (and genes) observed to behave similarly to Mendel’s ‘units’
Mendel’s work in the mid 20th century
Structure of DNA was discovered, as was an understanding of how genes function
Genetic engineering: potato crops
1) what’s the genetic modification?
2) where did the genes come from??
3) benefits to the organism
4) benefits to humans
1) made it resistant to disease
2) a different potato plant (wild potato)
3) doesn’t get the disease, lives longer
4) more potatoes for us to eat
Genetic engineering: soy bean
1) what’s the genetic modification?
2) where did the genes come from??
3) benefits to the organism
4) benefits to humans
1) made it resistant to herbicides
2) bacteria
3) no real benefit
4) more food
Genetic engineering: rice (golden rice)
1) what’s the genetic modification?
2) where did the genes come from??
3) benefits to the organism
4) benefits to humans
1) got more vitamin A in it
2) one from a daffodil, one from a soil bacterium
3) no real benefit
4) healthier diet
Genetic engineering: bacterium E.coli, fungus yeast
1) what’s the genetic modification?
2) where did the genes come from??
3) benefits to the organism
4) benefits to humans
1) produce human insulin
2) extracted from humans and inserted
3) no benefit
4) good for those who are diabetic
How does genetic engineering work?
- DNA is extracted from pancreas cells
- the insulin gene in a fragment of the pancreatic DNA, an enzyme is used to isolate the gene that codes for insulin production
- a plasmid from a bacterial cell is cut open using the same enzyme
- the insulin is inserted into the plasmid
- the plasmid is put back into the bacterial cell
- the genetically modified bacteria are cultured
- the genetically modified bacteria are growing in fermenters the product is removed and processed into human insulin
How does genetic engineering occur?
- Plants are exposed to a particular disease
- some plants are found to be resistant to the disease
- the gene responsible for disease resistance is identified through research on the resistant plants
- the desired gene is removed using enzymes
- embryos of the target plant are selected, so they can develop with the desired characteristics
- the desired gene is inserted into the genetic material of a bacteria or a virus and transferred to target the plant
- the embryos grow and reproduce to make many crop plants
- the crops are now all disease resistant
What is gene therapy?
- a deactivated virus is used as a vector to transfer a gene into the cell, lots of trials are underway
- this technique is being developed to treat some inherited disorders
- most gene therapies are in the experimental stages
What are the advantages of genetic engineering?
- more food supply
- healthier food
- GM crops are already being grown without any problems
- diseases can be treated
- nutrients can be added to diets e.g. vitamins
What are the disadvantages of genetic engineering?
- ethical issues
- expensive
- don’t know full effects
- growing GM crops may reduce biodiversity
- GM could cause allergies
- transplanted genes may get into the environment
What is genetic variation?
Many of our differences arise as a result of our genes
Identical twins have identical DNA
As a result, their features are nearly identical
What is environmental variation?
Things affected by the environment
What are a few reasons for selective breeding in animals?
- animals which produce more milk
- animals which produce more meat
- domestic dogs with gentle natures
Describe the process of selective breeding
- The animal breeder selects the sheep from the flock with the most muscle
- Offspring are produced from the sheep selected
- Some of the offspring are more muscular than others
- The most muscular sheep are selected and bred to produce offspring
- An increased number of the population will be muscular
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
Describe the process of natural selection
- There is always wide variation between the organisms within a species due to mutations
- Individuals within a species will be in competition for resources
- The best adapted organisms (i.e. the most successful competitors) are more likely to survive - this is known as ‘survival of the fittest’
- The successful organisms that survive are more likely to reproduce and pass on their genes for successful characteristics to their offspring
What are the conditions needed for microbes to carry out decay?
Oxygen
Warmth
Moisture
What is a fossil?
Remains of an organism that died thousands of years ago
How are fossils formed?
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- when parts of the organism are replaced by minerals as they decay
- as preserved traces of organisms, such as footprints, burrows and rootlet traces
Define species
Individuals that resemble one another and can breed together to produce fertile offspring
Describe the process of speciation
- geographical separation
- different environmental conditions
- mutations lead to new alleles
- best adapted in each area survive, breed and pass alleles onto offspring
- speciation (populations can no longer breed to produce fertile offspring)
Why was Lamarck’s theory for evolution not widely accepted?
Changes which occur to an organism during its lifetime are environmental, only genes can be inherited
Who was the theory of natural selection and evolution proposed by?
Charles Darwin in his book ‘On the origins of Species’ (1859)
At the same time, Alfred Russel Wallace also proposed the same theory
How does Lamarck’s theory differ from Darwin’s and Wallace’s theory?
- Darwin and Wallace said that variation in characteristics=characteristics are already present , whilst Lamarck said that changes through your lifetime can be inherited
- Wallace and Darwin said that only those animals who are already adapted are the ones to survive, whilst Lamarck said the animals can change to adapt to survive
Why were people against Darwin’s theory on evolution?
There wasn’t enough evidence
Lack of knowledge of genes and DNA
It goes against religious beliefs
Define extinction
When no living individuals of a species remain
How can a species become extinct?
- the environment changes too quickly (destruction of habitat)
- a new predator kills them all (humans hunting them)
- a new disease kills them all
- they don’t compete with another (new) species for food
- a catastrophic event happens that kills them all (volcanic eruption, collisions with asteroids)
