Inheritance, Variation and Evoloution Flashcards
Meiosis
A special type of cell division producing gametes
Happens in sex organs
Ovaries and testes
Gametes contain half the number of chromosomes 23. This is called haploid.
Normal body cells contain 46 chromosomes. This is called diploid.
Meiosis results in variation
Diploid cells have pairs of chromosomes- Why?
One maternal and one paternal
In this pair the chromosomes are said to be homologous
what does sexual reproduction involve
fusion of male and female gametes, bc there are 2 parents the offspring contain a mixture of their parents genes
the mixture of genetic information produces what?
variation
what happens in asexual reproduction?
only one parent
no fusion of gametes
no mixing of chromosomes
no genetic variation between parent and offspring
the offspring are genetically identical to the parent
clones
what are the stages of meosis?
1) genetic information duplicates forming 2 armed chromosomes - one arm of each chromosome is an exact copy of the other arm. after replication the chromosomes arrange themselves into pairs
2) in the first division the chromosome pairs line up at the centre of the cell
3) pairs pulled apart so each new cell has one copy of each chromosome. some of mothers and fathers chromosomes go into each new cell
4) in the second division, the chromosome line up again at the centre of the cell. the arms of the chromosomes are pulled apart
5) four gametes are made each with only a single set of chromosomes in it. each gamete is genetically different from the others because the chromosomes all get shuffled up during meiosis each gamete only gets half of them, at random
what happens in mitosis that makes up a whole organism?
after 2 gametes have fused during fertilisation, mitosis , means the new cell divided to make a copy of itself, this keeps happening to produce lots of cells in an embryo. as the embryo develops these cells then start to differentiate into different types of specialised cells that make up an entire organism
what happens in sexual reproduction?
male and female gametes fuse. offspring have two parents so the offspring genes are a mix of mum and dads genes
how many chromosomes are in every human cell?
23 pairs
22 are matched pair of chromosomes that control…..
characteristics
the 23 pair are labelled…..
XX or XY
what do the XX and XY chromosomes decide?
your sex
males have ………. chromosme
XY
females have an ,,,,,,,,,,,,,,,,,,,,,,,,,,, chromsome
XX
punnet square for a boy
50 % chance
what genes you inherit contol what ………………..
characteristics you develop
what is a homozygous gene
when an organism has 2 alleles for a particular gene that are the same
what is a heterozygous
when 2 alleles for a particular gene are different
what is the dominant allele
When displayed the characteristic is always shown
Can be heterozygous or homozygous
E.g BB or Bb
Recessive alleles:
Only shown when the alleles are the same (homozygous)
E.g bb - blue eyes
phenotype
normal
what is cystic fibrosis caused by
a recessive allele
what is polydactyly caused by
a dominal allele
GENOTYPE
The alleles the person has
PHENOTYPE
The characteristic displayed by the alleles
DOMINANT
The stronger allele, always shown in the phenotype
RECESSIVE
The weaker allele, only shown in the phenotype if homozygous
HOMOZYGOUS
Both alleles are the same
HETEROZYGOUS
One dominant and one recessive allele present
ALLELE
An alternative copy of a gene
CHROMOSOME
A thread –like structure containing DNA and protein that you inherit from your parents
GENE
A small section of DNA that codes for a particular characteristic
DNA
Stands for Deoxyribonucleic Acid.
Huntington’s Disease
Very rare but very serious.
Nerve cells in brain degenerate.
Incurable and fatal
what is embryo screening
Tests are now available to show if people carry a faulty allele.
People can test for these alleles before they start trying for a baby.
Embryos can be screening before implantation in IVF
Also the fetus during pregnancy can be screened
Both of these carry ethical issues
Both can risk miscarriage.
what are the 3 types of embryo screening?
Amniocentesis
Chorionic Villus Sampling
Pre-implantation genetics
what are the 3 types of embryo screening?
Amniocentesis
Chorionic Villus Sampling
Pre-implantation genetics
Amniocentesis:
Carried out at 15-16 week pregnancy.
Involves taking some fluid around the fetus.
This fluid will contain fetal cells for screening.
amniotic fluid draw with a needle under ultrasound guidance
Amniocentesis:
Carried out at 15-16 week pregnancy.
Involves taking some fluid around the fetus.
This fluid will contain fetal cells for screening.
amniotic fluid draw with a needle under ultrasound guidance
Chorionic Villus Sampling:
Taking cells from a part of the placenta whilst mother is pregnant
It is analysed for genetic disorders
If they are found to have genetic disorders the pregnancy can be terminated
sampling villi of placenta
what are the two methods of Chorionic Villus Sampling:
transcervical method - catheta through vagina into uterus
transabdominal method - needle into uterus
Pre-implantation genetics:
Diagnosis during IVF
Embryos are screened for genetic disorders
Prevents a pregnancy affected by a genetic condition
Only healthy embryos are placed into the uterus of the
mother, the others are discarded.
pros of genetic screening
treating the disorders costs the gov money
there are laws to stop it going too far
stop people from suffering from genetic disorders
cons of genetic screening
Risk of miscarriage of a healthy fetus
Always a risk of a false positive/negative
Expensive testing
Does not take into account future cures for disease
designer babies people may want to pick the most desire able one
what are the 2 types of variation?
Genetic variation
Environment variation
what are 4 examples of genetic variation?
Eye colour
Natural hair colour
Blood group
Some inherited diseases
why do children look like their parents?
Children look like their parents because of genetic information passed on in gametes (sex cells).
what is the order of largest to smallest for gene, chromosome, nucleus and DNA?
(largest) nucleus.chromosomes genes.DNA. (smallest)
WHat would be the best way to test whether a trait is inherited or if it has been affected by your environment?
scientists study twins adopted by different families compared to identical twins brought up together and non-identical twins
what are some examples of environmental variation
Scars, accents, drinking when pregnant, tattoos
what are some examples of combined variation?
Height, weight, skin colour
what are the two types of variation on a graph?
continuous and discontinuous
continuous:
wide range on values between two extremes
Continuous variation is represented as a line graph or histogram. eg height
no distinct categories
controlled by a lot of genes
strongly influenced by environment
discontinuous:
there are distinct groups
Discontinuous variation is represented as a Bar Graph.
Example: Blood groups (A, B, AB or O)
controlled by few genes
unaffected by enviroment
what are some examples of continuous variation?
Human body mass
Human hand span
Human heart rate
Human neck size
Human shoe size
Human height
Body length in a specific
species of fish
Number of leaves on a
specific species of tree
Number of petals on a daisy
Bean seed mass
Number of fruits on an apple tree
what are some examples of discontinuous variation?
Human fingerprint types
Attached or unattached earlobes in humans
Human blood group types
Ability or inability to roll tongue
Eye colour
Smooth or wrinkled seed coats in a pea seed
White or red eye in a fruit fly
Green or variegated leaf in a spider plant
White or coloured flower in a pea plant
what is the theory of evolution?
all of today species have evolved from simple life forms that first started to develop over 3 billion years ago.
What was Darwin’s theory?
Organisms evolve due to natural selection
Only the best suited organism to the environment will survive
Those that survive will reproduce and pass on their genes (and characteristics) onto their offspring
Gradually, a species will change over time.
Darwin’s work
From his travels, Darwin noticed that animals had similarities on different islands in the Galapagos. He observed finches on these islands and noticed that their beaks were different due to the food that was available.
what is speciation?
over a long period of time the phenotype of organisms can change so much because of natural selection, that a completely new species is formed.
when does speciation happen?
when populations of the same species change enough to become reproductivley isolated - this means they cant interbreed to produce fertile offspring.
survival of the fittest:
darwin concluded that the organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive
species become extinct for these reasons:
the environment changes too quickly (eg destruction of a habitat)
a new predator kills them all (eg humans hunting them)
a new disease kills them all
they cant compete with another new species for food
a catastrophic event happens that kills them all (eg volcanic eruption)
what is an example of an extinct species
dodos
humans hunted them and introduced other animals which ate all their eggs and we destroyed the forest where they lived.
Natural Selection
Mechanism for evolution
Organisms best adapted to their environments more likely to survive to reproductive age
Favourable characteristics are passed on
Produces organisms that are well adapted to their environment
what is selective breeding?
when humans breed plants and animals for particular genetic characteristics.
what features or characteristics are selectivity bred
animals that produce more meat or milk
crops with disease resistance
dogs with a good, gentle temperament
decorative plants with big or unusual flowers
what is the process of selective breeding?
1) from your existing stock select the ones which have the characteristics you desire
2) breed them with each other
3) select the best of the offspring and breed them together
4) continue this process over several generations and the desirable trait gets stronger. eventually all the offspring will have the characteristic.
how is selective breeding used in agriculture?
it can be used to improve yields for example:
to improve meat yields a farmer could breed together the cows and bulls with the best characteristics for producing meat eg large size. after doing this for several generations the framer should get cows with a very high meat yield.
what is the main problem with selective breeding?
it reduces the gene pool:
the number of different alleles in a population decreases
this is because of inbreeding
inbreeding causes health problems because there is more chance of the organisms inheriting harmful genetic defects
example of a problem with inbreeding in dogs
some dog breeds are susceptible to certain defects because of inbreeding - eg pugs often have breathing problems
what is another problem with selective breeding?
is a new disease appears because there is not much variation in the populations if one organism is susceptible to the disease then the rest of the stock will be
how does genetic engineering work?
1) a useful gene is isolated from one organisms genome using enzymes and is inserted into a vector
2) the vector is usually a virus or a bacteria plasmid, depending on the type of organism that the gene is being transferred to.
3) when the vector is introduced to the target organism, the useful gene is inserted into its cells
what can genetic engineering be used for?
manufacturing insulin
crops which produce a greater yield
finding out where genes are expressed in the body
crops resistant to disease
GM disadvantages
Genetically modified organisms
may be expensive
Need for long term studies
Effects may be passed on to
other crops, e.g. weed resistance
spreading from crops to weeds
Ethical issues about abortion
Risk of miscarriage or “false
positives” with amniocentesis
GM advantages
Improving crop yield
Improving resistance to
pesticides
Extend shelf-life
Manufacture a certain chemical
(e.g. insulin)
Convenience
Current medical research into
using genetic modification to
overcome inherited disorders
what are fossils?
the remains of organisms from many thousands of years ago which are found in rocks
fossils form in rocks in one of 3 ways:
1) from gradual replacement by minerals
2) from casts and impressions
3) from preservation in places where no decay happens
fossils from gradual replacement by minerals:
1) teeth, shells, bones which don’t decay easily can last a long time when buries.
2) they are replaced by minerals as they decay, forming a rock like substance shaped like the original hard part.
3) the surround sediments also turn to rock but the fossil stays distinct inside the rock and eventually some digs it up
fossils from casts and impressions:
1) fossil are formed when an organism is buried in a soft material like clay. the clay hardens around it and the organism decays, leaving a cast of itself. an animals burrow or a plants roots can be preserved as casts
2) footprints can also be pressed into these materials when soft, leaving an impression when it hardens
fossils from preservation in places where no decay happens:
1) in amber and tar pits there’s no oxygen or moisture so decay microbes cant survive
2) in glaciers its too cold for the decay microbes to work
3) peat bogs are too acidic for decay microbes
How do bacteria become resistant to antibiotics?
1) in bacteria there is genetic variation due to mutations
2) a mutation can make a bacterium resistant to antibiotics
3) if an antibiotic is used, all of the bacteria are killed, apart from the bacterium that is resistant to antibiotics
4) the antibiotic stain survives and reproduces, without any competition form other bacteria
5) over time the population of the resistant stain increases
6) the resistant stain now spreads, because people are not immune to it, and there is no effective treatment
How can antibiotic resistance be prevented?
Prevent overuse of antibiotics
Finish the course of antibiotics
Restrict the use of antibiotics in agriculture
Prevent overuse of antibiotics:
If they are over used it gives bacteria more chance to mutate and form an antibiotic resistant strain.
Antibiotics can also kill some of the harmless bacteria which can create more resources and space for the harmful bacteria to grow.
Finish the course of antibiotics:
To ensure that all bacteria are killed by the antibiotic, therefore none survive to mutate and form resistant strains.
Restrict the use of antibiotics in agriculture:
Antibiotic resistant strains can often arise in animal pathogens which can then be transferred to human pathogens
MRSA
MRSA can spread from person to person by skin-to-skin contact or someone who is infected or is a carrier, by contaminated wound dressings or bed sheets.
Hospital staff can ensure a reduction in the spread of MRSA by ensuring very strict hygiene and hand-washing protocols amongst hospital staff, visitors and patients. Patients should be regularly screened for the bacteria and isolated if they are infected. Try and limit transfer of patients between hospitals, especially if infected with MRSA.
why has antibiotic resistance increase nowadays?
Antibiotic resistance has increased over recent years because doctors have been prescribing antibiotics regularly over the past few decades. People have also been going to the doctors more when they are only a little bit ill or have a virus. Antibiotics have also been used in agriculture and passed down in the food chain.
Carl Linnaeus
living things are divided into kingdoms and then subdivided into smaller and smaller groups : kingdom, phylum, class, order, family, genus, species. according to their characteristics and the structures that make them up
species defintion:
A species is a group of organisms that can breed together to produce fertile offspring.
what are the 7 taxa:
kingdom king
phylum Phillip
class came
order over
family for
genus good
species soup
what are the 3 domains?
archaea - primitive bacteria, found in extreme places eg hot springs or salt lakes
bacteria - true bacteria eg E.coli
eukaryota - eg fungi, plants animals and protists
what are the 5 kingdoms
Animalia
Plantae
Fungi
Protoctista
Prokaryotae
Animalia kingdom
Multicellular (made of many cells)
Heterotrophic (can’t make their own food, so no chlorophyll)
Cells do not have cell walls
Cells have complex structure
Cells have a nucleus
Plantae kingdom
Multicellular (made of many cells)
Autotrophic (make their own food using chlorophyll)
Cells have cell walls made of cellulose
Cells have complex structure
Cells have a nucleus
Fungi kingdom
Multicellular (made of many cells)
Saprophytic (leech food from other things, so no chlorophyll)
Cells have cell walls, but are not made of cellulose
Cells have complex structure
Cells have a nucleus
Protoctista kingdom
Mostly Unicellular (made of single cells)
Cells have complex structure
Cells have a nucleus
Eg Algae, Amoebas,
Prokaryotae kingdom
Unicellular (made of single cells)
Cells have simple structure
Cells have no nucleus
Eg bacteria, salmonella
How does the structure of a prokaryotic cell differ from a eukaryotic cell?
Prokaryote
No nucleus
Loop of DNA – no chromosomes
No membrane-bound organelles
Eukaryote
Has a nucleus
Nucleus contain chromosomes
Has membrane-bound organelles
what are the 3 domains called?
archaea
bacteria
eukaryota
archaea domain:
organisms in this domain are primitive bacteria. they are often found in extreme places such as hot springs and salt lakes
bacteria domain:
true bacteria like E. coli and Staphylococcus.
eukaryota domain:
broad range of organisms including fungi, plants, animals and protists
