INHERITANCE, VARIATION AND EVOLUTION Flashcards
What is DNA?
A chemical called deoxyribonucleic acid and is what all of the genetic material in a cell is made from
It contains coded information
Where is DNA found?
In the nucleus of a cell in chromosomes
What is the structure of DNA?
It is a polynucleotide and has a double helix structure
What is a gene?
A small section of DNA found on a chromosome
Each gene codes for a particular sequence of amino acids to make a specific protein (say in what order to put the AA)
What is a genome?
The entire set of genetic material in an organism
What are DNA strands?
They are polymers made up of lots of repeating units called nucleotides
What does a nucleotide contain?
Phosphate (circle)
Sugar (hexagon)
Base (square)
What are the different bases and which ones to they connect with?
A - T
C - G
How many bases codes one amino acid?
3
Where are proteins made?
In ribosomes (in the cytoplasm)
How are proteins made? - protien synthesis
A molecule called mRNA (copy of the DNA code) acts as a messenger between the nucleus and ribosomes carrying the correct amino acids in the correct order
What happens when a chain of amino acids have formed?
It folds into a unique shape which allows the protein to perform the task it is meant to do
What are some examples of proteins?
Hormones
Catalysts (enzymes)
Structural proteins
What is a mutation?
A random change in an organism’s DNA (can be inherited)
What do mutations do?
They change the sequence of DNA bases in a gene which produces a genetic variant
This leads to a change in protein made as there is not the correct amino acids to form it
What could happen if a mutation occurs and the proteins shape is changed (enzymes)?
The enzymes active site is changed so the substrate will no longer be able to bind to it
What is an insertion mutation?
When a new base is inserted into the DNA
Changes the way the group of 3 bases is read to code for an amino acid (can change more than one)
What is a deletion mutation?
When a random base is deleted from the DNA base sequence (like insertions)
What is a substitution mutation?
When a random base is changed to a different base in the DNA base sequence
What happens during sexual reproduction?
Mother and father produce gametes by meiosis (egg and sperm cells)
Each one contains 23 chromosomes
Egg and sperm cell then fuse together to form a zygote with the full number of chromosomes (46)
What happens during asexual reproduction?
The offspring is genetically identical to the parent
Happens by mitosis
Clone is produced
What are the steps of meiosis?
Cell duplicates its genetic information (chromosomes arrange themselves into pairs)
Cell divides into 2 and the two lines of chromosomes are split up
In the second division the 2 cells divide into 4 and the chromosomes are pulled apart
Four gametes are produced each with only a single set of chromosomes
How does sexual reproduction have an advantage over asexual reproduction?
In sexual reproduction the organism inherits genes from both its parents which produces variation
This increases the chance of a species survival (natural selection)
How does asexual reproduction have an advantage over sexual reproduction?
Only needs one parent so less energy and faster
What are the 23rd pair of chromosomes in the body?
XY (male) or XX (female)
What is an allele?
A different version of a gene/sequence of DNA
What is homozygous recessive?
When the two alleles are the same and are both recessive
(bb)
What is homozygous dominant?
When the two alleles are the same and are both dominant
(BB)
What is heterozygous?
When the two alleles are different so one is recessive and one is dominant
(Bb)
What is the only way an organism can display a recessive characteristic?
If both alleles are recessive
What is your genotype?
The combination of alleles you have
What is your phenotype?
What characteristics you have as a result of your genotype
What allele is cystic fibrosis caused by?
A recessive allele
What allele is polydactyly caused by?
A dominant allele
What is cystic fibrosis?
Genetic disorder which results in the body producing a lot of thick sticky mucus in air passages and pancreas
What is poldactyly?
When a baby is born with extra fingers or toes
What are the benefits of embryo screening?
Helps stop people suffering
Treating disorders costs the government a lot of money
Laws in place (cannot select gender of baby)
What are the problems of embryo screening?
Implies people with genetic disorders are ‘undesirable’
Expensive
People can pick the most desirable qualities that they want
What is embryo screening?
Embryos are fertilised in a lab and then implanted in a woman’s womb
A cell can be removed from the embryo and its genes can be analysed which can detect any genetic disorders
What did Mendel discover by observing pea plants?
Characteristics in plants are determined by hereditary units
(one unit from each parents passed onto offspring which can be dominant or recessive)
What are gametes?
Reproductive/sex cells
What causes genetic variation?
Combining of genes from two parents so no two of the species are genetically identical
What are mutations?
Changes to the sequences of bases in DNA
How can mutations create variation?
Change to base so change to protein therefore can result in a new phenotype which could be better suited to the environment then natural selection
What is the idea of ‘survival of the fittest’?
Organisms with more suitable characteristics for the environment would be more successful competitors and would be more likely to survive to reproduce and pass on those genes
When does speciation happen?
When the same species change enough to become reproductively isolated (can’t interbreed to produce fertile offspring)
What is speciation?
When the phenotype of an organism changes so much because of natural selection that a completely new species is formed
What are reasons for extinction?
Environment changes too quickly
New predator kills them all
New diseases kill them all
Can’t compete with another (new) species for food
Catastrophic event kills them (volcano)
What did Lamarck believe?
That changes that an organism acquires during its lifetime will be passed on to its offspring
What is selective breeding?
When humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population
What is a disadvantage of selective breeding?
Reduces the gene pool (number of different alleles) which is inbreeding
What are the dangers of inbreeding?
Can cause health problems as there is more chance of e organism inheriting harmful genetic defects
How is genetic engineering carried out?
Useful gene isolated from organism using enzymes and put inside a vector which is introduced to an organism and the gene is inserted into its cells
What are the cons of genetically modified crops?
Affect number of wildflowers (and population of insects) which reduces farmland biodiversity
Might not be safe
Weeds may pick up the herbicide resistant gene
What are the pros of genetically modified crops?
Increase yield
Engineered to contain nutrients that developing nations are missing
What is isolation?
Where populations of the same species are separated (geographically due to physical barriers)
What happens when species are isolated?
Environments are different (climate etc) therefore different characteristics will become more common in each population due to natural selection
How can bacteria become antibiotic resistant?
Random mutations lead to changes in characteristics which can be resistant to particular antibiotic therefore antibiotic-resistant strains form
Bacteria reproduces rapidly so evolve quickly
Why should you take the full course of antibiotics?
So all of the bacteria is destroyed so there are none left to mutate and develop into antibiotic-resistant strains
What is the order of the Linnaean system (Carl Linnaeus 1700’s)?
Kingdom
Phylum
Class
Order
Family
Genus
Species
What is the three-domain system (Carl Woese 1990)?
Archaea (primitive bacteria)
Bacteria (true bacteria)
Eukaryota (fungi, plants, animals and protists)
How do you figure out a species two-part Latin name?
Genus + species
What do evolutionary trees show?
Show how scientists think different species are related to each other (common ancestors)
