topic 6- inheritance , variation and evolution Flashcards
what is DNA
deoxyribonuclei acid
found in the nucleus
the genetic material in the nucleus of a cell is composed of a chemical called DNA
DNAi is a polymer made up of 2 strands forming a double helix
the dna is contained in structures called chromosomes
what is a gene
it is a small section of your DNA on a chromosome
each gene codes for a particular sequence of amino acids to make a specific protein
only 20 amino acids are used to make thousands of different proteins
genes tells cells what order to put the amino acids together and what type of cell to make
what is a genome
the entire genetic material of that organism
why is understanding the genome important
allows scientists to identify the genes in the genome that is linked to different types of diseases
k woing what genes is linked to what inherited diseases to help develop treatments for it
use to treck migration patterns for humans in the past
structure of dna
DNA is a polymer made of t repeating nucleotide units
each nucleotide consists fo sugar , phosphate group and one base
DNA consists of 4 diiferent bases - A,C,G and T
each base llinks to a base on the opposite strand on the helix
complimentary base pairing
A WITH T
G WITH c
the order of bases ina gene decides the order of amino acinds in a protein
a sequence of 3 bases is the code for a particular amino acid
non coding
some parts of the dna dont code for proteins
some of them switch genes on and off
so they control whether a gene is expressed
how are proteins made
proteins are made in the cel, cytoplasm on the tiny structures called ribosomes
to make proteins,ribosomes use the code in the DNA [dna is found in the nucleus and cant move out of it because of its size ] so the cell needs to get the DNA to the ribsome , this is done using a molecule called mRNA [which is made by copying the code from DNA
the mRNA acts as a messanger between the DNA and the ribosome as it carries code betwwen the 2
the correct amino acids are brought to the ribosmones in the correct order by carrier molecules
types of proteins
enzymes - acts as a biological catalysts to speed up chemical reactions in the body
hormones - used to carry messages around the body
structural proteins - are physically strong eg collagen is a structural protein that strengthens connective tissue
what is mutation
a random change in an organisms DNA
can be inherited
mutations occurs continuously
most mutatins dont alter the protein and if altered it doesnt usually affect the function or appereance
does does mutation affect nono-coding DNA
it alters how genes are expressed
types of mutation
insertation
deletions
substitutions
deletions
this is when a random base is deleted from the DNA base sequence
they change the way the base sequence is ‘read’ and have knock on effects further down the sequence
substitution
when random base in the dna base sequence is changed to a different base
insertions
where a new base is inserted into the dna base sequence where it shouldnt be
insertation changes the way the groups are ‘read’ so it changes the amoni acids that they code for
insertion can change more than one amino acid as it has a knock on effect on the bases further down the sequence
what is sexual reproduction
when genetic information from two organisms are combined to produce offspring which are geneticaly different to either patient
the mother and the father produce gametes by meosis
gametes contain 23 chromosomes [half of the normal cell]
fertilisation
the egg cell and sprm cell come together to form a new cell with the full number of chromosomes
offsprings receive a mixture of chromosomes from both parents esplaining why we inherit feturs from both of them
the mixture of genetic informtion produces variation in the offspring
asexual reproduction
there is only one parent so the offspring is genetically identical to the parent
asexual reproduction happens by mitosis
clone - the new cell has exactly the same genetic information as the parent cell
no fusion of gametes .no mixture of chromosomes and no gentic variation
e.g- bacteria,some plants and animals
meiosis
before a cell starts to divide it must duplicate its DNA
[forming exact 2 armed chromosomes ]
after the duplication the chromosomes arrange themselves in pairs
in the first divison -the chromosomes line up at the centre of the cell
the pair is then pulled apart to the new cell has one cpy of each chromosome[from both parents]
in the second divison- the chromosomes line up at the centre again and the arms are pulled apart
you get 4 gamates which are geneticvally different
advantages of sexual reproduction
produces variation in offspring
if the environment changes variation gives a survival advantage by natural selection
natural selection can be sped up by human in selective breeding to increase food production
advantages of asexual
only one parent needed
no mate needed so it is more time and energy efficent
faster than sexual reproduction
many offspring can be produced if conditions are favourable
examples of organisms that do both sexual and asexual
malaria parasites reproduce asexually in the human most but sexually in the mosquito
many fungi reproduce asexually by spores but also sexually to give variation
many plants produce seeds sexually but also reproduce asexually by runners such as strawberry plants or bulb division such as daffodis
What is a chromosome
A long molecule of DNA found in the nucleus
Each chromosome carries many genes
Allele
A alternative version of a gene
Dominant allele
The allele for the characteristic that’s shown by an organism
If two different alleles are present for that characteristic .
Recessive allele
An allele whose characteristic only appear in an organism if there are two copies present
Homozygous
Where an organism has 2 alleles for a particular gene that are the same
Heterozygous
Where an organism has two alleles for a particular gene that are different
Genotype
What allele you have
Phenotype
The characteristic you have
Like brown eyes
Cystic fibrosis
A disorder of cell membrane caused by a recessive allele f
Carries by about 1 in 25 people
For it to be passed on both parents carry it or have the disorder themselves
Polydactyly
Having extra fingers or toes
Dominant Gene D
Can be inherited if one parent is a carrier
50% chance of getting it
For or against embryotic screening
For - help stop people suffering
Treating disorders cost a lot for the government
Against - screening is expensive
Increases prejudice
Everyone would want to pick the most desirable features
Genetic cross to show sex inheritance
50:50 ratio
What is variation
Differences in the characteristics of individuals in a population
What causes variation
Types of variations
The genes they have inherited (genetic causes )
The conditions in which they have developed ( environmental causes )
A combination of both
How does genome and its interactions with environment have an influence on the development of the phenotype
An organisms characteristics are determined by the genes inherited from the parents
These genes are passed on in sex cells from which the offspring develops.
The combining of genes from two parents causes, genetic variation, some characteristics are determined only by genes
for instance, eye Color, blood group, and inherited conditions
Mutation in variation
Mutations are changes to the sequence of bases in a DNA. Usually mutation has little effect on the phenotype, but occasionally it changes the characteristics slightly resulting in a new phenotype being seen in the species.
If the environment changes and the new phenotype makes an individual more suited to the new environment, it can become common throughout the species by natural selection 
What is evolution
a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
Explain the theory of natural selection
The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago
Impact of selective breeding of food plant and domesticated animals
It reduces gene pool (inbreeding )
Health problems
New disease
What is selective breeding
Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals
Characteristics that are looked for
• Disease resistance in food crops.
• Animals which produce more meat or milk.
Domestic dogs with a gentle nature.
• Large or unusual flowers
What is genetic engineering
process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
How have pants been genetically engineered
Plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits.
How have bacteria been genetically engineered
Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes
Benefits and disadvantages of GM
Pro - can increase yield
GM can provide more nutrients for food that lack it
It is already being used without problems
Cons - affect number of wild flowers (reducing farmland diversity)
Not safe / more research needed
Maybe get out in natural environment
Explain Genetic engineering
In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
What are GM crops
Crops that have had their genes modified in this way are called genetically modified (GM) crops. GM crops include ones that are resistant to insect attack or to herbicides. GM crops generally show increased yields
Describe genetic engineering
• enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus
the vector is used to insert the gene into the required cells
genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics
What is tissue culture
using small groups of cells from part of a plant to grow identical new plants. This is important for preserving rare plant species or commercially in nurseries
What is cutting
an older, but simple, method used by gardeners to produce many identical new plants from a parent plant
Embryo transplant
splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers
Adult cell cloning
• The nucleus is removed from an unfertilised egg cell.
• The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell. An electric shock stimulates the egg cell to divide to form an embryo.
• These embryo cells contain the same genetic information as the adult skin cell.
• When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development
Pro and con of cloning
Charles Darwin
Charles Darwin, as a result of observations on a round the world expedition, backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils, proposed the theory of evolution by natural selection.
Individual organisms within a particular species show a wide range of variation for a characteristic. Individuals with characteristics most suited to the environment are more likely to survive to breed successfully. The characteristics that have enabled these individuals to survive are then passed on to the next generation
Mendal
In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged. In the late 19th century behaviour of chromosomes during cell division was observed
In the early 20th century it was observed that chromosomes and
Mendel’s ‘units’ behaved in similar ways. This led to the idea that the
units’, now called genes, were located on chromosomes.
In the mid-20th century the structure of DNA was determined and the
mechanism of gene function worked out
Evidence of Darwin’s theory of evolution
The theory of evolution by natural selection is now widely accepted. Evidence for Darwin’s theory is now available as it has been shown chat characteristics are passed on to offspring in genes. There is further
evidence in the fossil record and the knowledge of how resistance to
antibiotics evolves in bacteria.
Extinction
Extinctions occur when there are no remaining individuals of a species still alive
Environment changing too fast
New predator
New disease
Weak
Catastrophic event
Fossils
Fossils are the ‘remains’ of organisms from millions of years ago, wh are found in rocks.
Fossils may be 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
Antibiotic resistant bacteria
Bacteria can evolve rapidly because they reproduce at a fast rate.
Mutations of bacterial pathogens produce new strains. Some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises. The resistant strain will then spread because people are not immune to it and there is no effective treatment
To reduce the rate of development of anti bacterial resistant strains
doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
the agricultural use of antibiotics should be restricted
Classification of living organism
Developed by Carl Linnaeus
kingdom,
phylum,
class,
order,
family,
genus
Species
New classification system
Carl woese
archaea (primitive bacteria usually living in extreme environment
bacteria (true bacteria)
eukaryota (which includes protists, fungi, plants and animals
