Inheritance, Variation and Evolution Flashcards
What shape is DNA
Double helix
What are chromosomes
Long molecules of DNA
What is a gene and what does it do
A short section of DNA found on a chromosome that codes for a specific protein
What is the genome
The entire set of genetic material within an organism
Why is knowing the entire human genome useful
Can identify which genes are linked to different types of disease
Can identify which genes are linked to inherited diseases
Can use the genome to track the migration that humans took from Africa
What are the monomers for DNA
Nucleotides
What is a nucleotide made up of
Sugar
Phosphate
Base
Which bases pair up with each other
A + T
C + G
How many bases code for 1 amino acid
3
What do non-coding parts of DNA do
Control whether or not a gene is expressed
How does protein synthesis happen
DNA Unzips
mRNA copies the code from the bases
moves into ribosomes in the cytoplasm
A tRNA carrier molecule carrying an amino acid
complementary bases attach
joins amino acid chain
then folds up uniquely to form a protein
Uses of proteins
Enzymes
Hormones
Structural proteins eg collagen
What is a mutation
A random change in an organism’s DNA
Can sometimes be inherited
Most mutations have little to no affect
A mutation in non-coding DNA may affect which genes are expressed
However some mutations can seriously affect a protein as it can change the way the fold up, meaning the substrate may no longer be able to bind to it
What are the different types of mutation
Insertions
Deletions
Substitutions
How many chromosomes does each gamete have in humans
23 (half)
What type of cell(in terms of difference) does sexual reproduction produce
Genetically different cells
What type of cells (in terms of difference) does asexual reproduction produce
Genetically identical cells
How are gametes produced
Meiosis
What happens in meiosis
Genetic information duplicates
In the first division the chromosome pairs line up at the centre of the cell
The pairs are pulled apart so each new cell only has 1 copy of each chromosome
(some of the father’s and some of the mother’s go into each cell)
In the second division the chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart
You end up with 4 gametes each with only a single set of chromosomes in it
Genetically different
What are the pros and cons of sexual reproduction
Pros:
Variation in offspring
Cons:
Slow(er)
Requires 2 organisms
Pros and cons of asexual reproduction
Pros:
Only 1 parent so time efficient
Quicker
Many offspring produced in favourable conditions
Cons:
Lack of variation
Examples of organisms that can do both (a)sexual reproduction
Malaria
Fungi
Strawberries
What chromosomes do males and females have
Males:
XY
Females:
XX
What are alleles
Different versions of genes
Humans have 2 alleles of each gene, one from each parent
What is your phenotype
The result of your genotype - your physical appearance
What is cystic fibrosis
A recessive condition that causes the body to produce lots of stick mucus in air passages and pancreas
For the child to have the disorder, both parents must carry the allele or have the disorder themselves
What is polydactyly
A dominant condition that causes the child to be born with extra fingers or toes
The parent that carries the defective allele will also have the condition
How can embryos be screened for genetic disorders and pros and cons
Removing cells before IVF
Also possible to get DNA from a child in the womb
Pros:
Can help stop suffering
Treating disorders costs the Government a lot of money
Cons:
Prejudice
Choosing desired characteristics
Expensive
What did Mendel discover
Observed plants and discovered ‘hereditary units’ from each parent
Discovered genes
What are characteristics influenced by
Genes and environment
What is Charles Darwin’s theory of evolution
That only the fittest survive and that beneficial characteristics are passed on
Nowadays we know that mutations occur during reproduction
What is speciation
When a new species is formed and cannot interbreed to produce fertile offspring any more
How does speciation occur
Environmental separation
Adapt
Change
Grow apart
Cannot interbreed
What is extinction and why does it happen
When no members of a species exist any more
Can happen due to:
Environment changes too quickly
New predator
New disease
Catastrophic event
Reasons why people disagreed with Darwin
Went against religious beliefs
Darwin couldn’t fully explain how these characteristics came about
Lack of other evidence
What did Lamarck believe
That if a characteristic was used a lot by an organism, it would be enhanced and then passed onto its offspring
What is selective breeding and pros and cons
Choosing which organisms to breed as they have desired characteristics
Pros:
Can get desired characteristics
Cons:
Reduces the gene pool which can lead to health problems
What is genetic engineering and pros and cons
Gene is cut using restriction enzymes and inserted into a vector
Then introduced into the target organism
Pros:
Increase yield of food
Can put nutrients into food
Cons:
Some people are against GM food
May affect the number of wild flowers
What are the 2 ways plants can be cloned
Tissue culture - a few plant cells in growth medium and hormones
Cuttings - snippets of the plant and then plant them (slower) but cheaper
What are the 2 ways you can clone animals
Embryo transplants - prize sperm and egg cells are taken
artificially fertilised
cloned embryos can be implanted into other animals
Adult cell cloning - remove the nucleus from an egg cell and place the nucleus from an adult body cell into the egg cell
electrically stimulated by shock and begins to divide
then implanted into females
Pros and cons of cloning
Pros:
Ideal offspring
Could lead to other scientific discoveries around ageing
Preserve endangered species
Cons:
Many clone humans in future
Lack of variation
3 ways fossils are formed
Gradual replacement by minerals
Casts and impressions
Preservation in places where decay does not happen
Who was Wallace and what did he do
Speciation and warning colours in animals
What are the ways things are classified
Kingdom
Phylum
Class
Order
Family
Genus
Species
Who came up with the classification system
Carl Linnaeus
