inheritance, variation, evolution Flashcards
what is asexual reproduction
only one parent and doesn’t contain any gametes
what is sexual reproduction
the fusion of male and female gametes
why do you inherit characteristics from both parents during sexual reproduction
because sexual reproduction is the fusion of male and female gametes, the offspring will have a mixture of both genes and therefore have genetic variation
what are gametes and give the three examples
cells that carry only have half of the genetic material
eggs and sperm
pollen and eggs
how are gametes made
miosis
why is there no genetic variation when asexual reproduction occurs
there is only one parent and therefore there is no mixing of genetic material creating identical clones of ofspring
what process do eukaryotes (such as plants and fungi) go through in order to reproduce asexually
mitosis
what process do prokaryotes (such as bacteria) go through in order to reproduce asexually
binary fission
what are the advantages of asexual reproduction
only one parent is needed and the process is very quick
- allows an organism to quickly colonise one area
what are the disadvantages of asexual reproduction
no genetic variation - if a new disease comes along and one offspring is susceptible to it its likely that all will be
- also means that they will have less chance of adapting to new conditions like a new climate
what are the advantages of sexual reproduction
leads to loads of genetic variation - less likely to get wiped out by a disease (some may be more resistant)
- can adapt to conditions - allow evolution to occur
what are the disadvantages of sexual reproductoin
- takes a lot more time and energy
what is a haploid cell
what is a diploid cell
haploid - cells containing half the genetic material of a normal cell
diploid - a cell that has undergone meiosis before fusing to another gamete cell therefore now containing two sets of genetic information from each parent to form an embryo
what is the first steps of meiosis
- replicating all of the cells DNA by replicating the chromosomes - creating an arm for each maternal and paternal chromosome
- they then line up in the centre of the cell in their pairs
- chromosomes then pulled to the poles of the cell and the whole cell splits
why is the distribution of DNA different in each cell that undergoes meiosis
when lining up in the centre, the chromosomes from the mother and father are in no particular order (left and right order) therefore different each time
- chromosomes are then randomly distributed with each half of the split cell receiving a different combination of maternal and paternal chromosomes
what are the second stages of meiosis
the chromosomes line up in the centre of the cell, this time the two arms of the chromosomes will be split to each pole of the cell
- cells then divide in half again
leaving us with four cells
what is the product of meiosis
four genetically unique cells that we call gametes that hold 23 chromosomes
what is DNA
the chemical all our genetic material is made of and determines what proteins a cell produces
what is DNA made of and what is the structure
polymers and is has two strands therefore forming a double helix
the DNA is split into 46 “sections” - chromosomes (which are tight coils) which we have 2x each type
why is the 23 chromosome different
they are sex chromosomes
women have two x chromosomes
males have one x and one y
what is a gene
a small section of DNA that codes for a particular protein (a sequence of amino acids)
“small segment of a chromosome”
how many different amino acids do we have what do amino acids combine to create
20 but they can be interlinked to create 1000s of different proteins
what is a genome
the entire set of genetic material in an organism
how has the identification of the entire human genome helped scientists
able to identify the specific genes that are linked to specific diseases and chose more affective treatments/ create more affective treatments
- also helped us be able to track our ancestors
what is an allies
a different forms of the same gene
what is the difference between homozygous and heterozygous
we have two copies of every gene (one from mother and one from father) meaning we have two allies of each gene. these can be the same allies (homo) or different allies (hetro)
what are dominant and recessive allies
when there are two different allies (hetro), they will either be dominant or recessive. the dominant allies will take dominance over the characteristic and that one will always be expressed. the only way for the recessive allies to be expressed is if both allies are recessive
what is genotype and phenotype
genotype - the collection of allies we have
(dominant/recessive etc)
phenotype - the characteristics we receive from the genotype
what is an inherited disorder
group of conditions that can be passed on in allies and can be inherited from parents
what are two examples of an inherited disorder
polydactyly and cystic fibrosis
explain the inherited disorder of “polydactyly”
when a baby is born with extra fingers or toes.
it is caused by a dominant allele
explain the inherited disorder of “cystic fibrosis”
it is caused by a recessive allele
it is a disorder of cell membranes which causes thick sticky mucus in different parts of the body - lungs and pancreas
what is embryo screening
when having an IVF, scientists will take a cell from the embryo to look at the genes and investigate weather they are carrying any genetic disorders
what are the pros and cons of embryonic screening
- reduce overall suffering as fewer people will suffer from health problems
- save a lot of money - treating disorders are expensive
- implies people with genetic disorders are less desirable
- future screening for other traits
what is variation
any difference between the individuals phenotype in a species or groups of organisms of any species
what is variation dependant on
genes and proteins yet also your environment
what is a mutation
change in the DNA code so that the protein it codes for may be different. most don’t have an effect on the protein and therefore don’t change the organisms phenotype
what is the survival of the fittest
some mutations are beneficial giving individual good characteristics which were being passed down to their offspring therefore more likely to survive
what is natural selection
individuals that are less adapted to the environment are less likely to survive
what is evolution
the development of any organism over a period of time in order to adapt and survive in their changing environment. this could lead to a change in the whole species or even a development of a new species
what is selective breeding
when you breed the best plant or animals in the population to create the best offspring and best allies for the best traits
how do we selective breed
select the best two in your population and breed them together over and over always picking the best offspring
what is the negatives of selective breeding
- reduces the gene pool of the population
- lead to inbreeding making offspring prone to diseases or inherited defects
- less variation therefore a pathogen could infect all plants at once
what is a gene pool
collection of different allies in a population and because we select the allies with the most wanted characteristics we are left with a smaller pool of allies
what is genetic engineering
modification of an organisms’ genome by inserting a gene from another species
what are two examples of genetic engineering we have completed to help in the medication industry
genetically modified sheep to produce a specific drug in their milk
genetically modified bacteria to produce the human hormone insulin to treat diabetes
how are we currently trying to use genetic engineering to cure inherited disorders (caused by faulty genes) and why is it proving difficult)
gene therapy - giving the person a healthy version of the gene
difficult - the faulty gene is in all the cells and therefore is difficult to transfer the new gene to every cell in the body - transfer at an early stage of development
pros and cons of genetically modified (engineered) crops
pros - easliy make crops have desireab characteristics - more fruit, resist diseases - more food for less money - important in developing counterues
- produce special nutrience
cons - we dont know exactly how genetically modified plants effect human health
- could make their way into the wild and effect the whole ecosystem
during genetic engineering, how is the gene transferred from one organism to another
- find the gene we want and cut section of DNA - “isolate it” using enzymes
- insert gene into a vector - virus or a bacterial plasmid
- introduce the vector to the organism which will then take in the vector and gene and begin to produce the protein the gene codes for
what is bacterial plasmid
little loops of DNA that bacteria hold
what are the two ways plants can be cloned
take cuttings, tissue culture
what is the main advantage of cloning plants
because it is genetically identical to the original plant we know exactly what characteristics the clone is going to have
how is plant cloning completed using the method of taking cuttings
a small piece of a plant is removed and the end is dipped in rooting powder which contains plant hormones encouraging the plant to grow and develop roots
how is plant cloning completed using the method of tissue culture
take the plant we want to clone and divide it into hundreds of tiny pieces, these small groups of cells are incubated with plant hormones, stimulating them to grow and develop. need sterile conditions
what are the benefits of using tissue culture to develop clones of plants
allows growers to produce hundreds of clones quickly and cheaply
to preserve rare species of plants
what are the two ways of cloning animals
embryo transfer, adult cell cloning
how is animal cloning completed using the method of embryo transfer
-start with sperm and egg cell from the mammal with desired characteristics
-fertilisation produces a fertilised egg which is then developed into an early stage embryo - not had a chance to specialise
-use a glass rod to split embryo into two
- transplant the two embryos into host mothers
how is animal cloning completed using the method of adult cell cloning
-remove a cell from the mammal and remove the nucleus which contains the genetic information
- take an unfertilised egg cell and remove the nucleus and replace with nucleus from other mammal
- give egg cell an electric shock to divide it and form embryo
-inserted into host mother
what is the benefit of adult cell cloning
we know the characteristics that the clone will have
what is Darwin’s theory of evolution
evolution occurred by natural selection
why wasn’t Darwin’s theory accepted and controversial
at the time people heavily believed in God and his creation of the world, Darwin’s theory went against this. scientists at the time also felt like there wasn’t enough evidence and people didn’t understand how characteristics were inherited
what did Jean Lamarck suggest
that when a characteristic is regularly used it becomes more developed and passed onto offspring
what is speciation
the process of how new species form
Who is Alfred Wallace and what did he want to know/ what did he find out
wanted to know how warning colours on animals evolved
- found out the theory of evolution by natural selection and him and Darwin put their theories together
what do you need in order for speciation to occur
a geographical barrier
explain the process of speciation
- if a species of an organism are on an island they are interbreeding spreading beneficial mutation
- if the species get separated by a geographical barrier there will no longer be interbreeding between two groups
- over time, natural selection will favour different allies on both sides meaning over generations the populations phenotypes will change
how did Mendel study inheritance
through carrying out breeding experiments of plants and analysing the ratios of characteristics in offspring
why was Mendel’s work not recognised until after his death
he couldn’t explain the mechanisms of inheritance as chromosomes were not discovered
what are the two types of evidence to support the theory of evolution
fossils and antibiotic resistant bacteria
what are fossils
the remains of organisms from millions of years ago which are found in rocks
what are the three ways in which fossils are formed
- parts of an organism that hasn’t decayed - if the conditions for decay weren’t present
- parts of the organism were slowly replaced by minerals in the decay process
- can be preserved traces of organisms like footprints
what are the problems with fossils
many early forms of life had soft bodies with little to no bones
what are the reasons for a species to go extinct
catastrophic event
changing weather patterns
new predator or disease
new more successful species evolved
how do fossils provide evidence for evolution
scientist can identify the age of fossils and use them to show the development over time
give an example of a resistant bacteria
MRSA
why does bacteria evolve quickly
because of their fast rate of reproduction
how does antibiotic resistence occur
- mutations occur in bacteria producing genetic variations
- certain strains of bacteria resistant to bacteria are not killed when antibiotic applied
- resistant strains survive and reproduce
- over time the population of resistant strain increases
how can we reduce the amount of antibiotic resistant bacteria
- only prescribe antibiotics when necessary
- completing the full course of antibiotics
- reduce the amount of antibiotics used in farming
what is the classification system created by Linnaeus
kingdoms, phylum, class, order, family, genus, species
how are organisms classified
their characteristics and structure
how do you name a species according to the binomial system
genus name followed by species name
why were new classification models developed
development in microscopy - better examination of organisms internal structures
improvement in understanding biochemical processes - such as DNA
what are the three domains and what are they
archaea - bacteria living in extreme conditions
bacteria - like inside body
eukarya - plants, animals, fungi, protist
how are evolutionary trees created
examine the DNA of different species and analyse how similar they are
