Inheritance,Variation,Evolution

Question 7

How often do mutations occur and does it alter protein

Answer 7

Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.

Question 8

What effects can mutation of dna have

Answer 8

Some can have a serious effect and can change the shape
● The substrate will not fit into the active site so it cannot act as a protein.
● A structural protein may lose its shape

Question 9

What do coding and non-coding dna do

Answer 9

The coding DNA that determines the proteins and their activity
The non-coding DNA that determines which genes are expressed

Question 10

What does gamete mean

Answer 10

An organism’s reproductive cell (egg in female and sperm in males), which has half the number of chromosomes (23)

Question 11

What does chromosome mean

Answer 11

A structure found in the nucleus which is made up of a long strand of DNA.

Question 12

What does gene mean

Answer 12

Gene-A short section of DNA that codes for a protein, and therefore contribute to a characteristic. Some characteristics are controlled by a single gene, such as fur colour in mice and red-green colour blindness in humans. However, most characteristics are the result of many different genes interacting.

Question 13

What does allele mean

Answer 13

The different forms of the gene - humans have two alleles for each gene as they inherit one from each parent.

Question 14

What does dominant allele mean

Answer 14

Only one (out of the two alleles) is needed for it to be expressed and for the corresponding phenotype to be observed.

Question 15

What dos recessive allele mean

Answer 15

Two copies are needed for it to be expressed and for the corresponding the phenotype to be observed

Question 16

What does homozygous mean

Answer 16

When both inherited alleles are the same (i.e. two dominant alleles or two recessive alleles).

Question 17

What does hetrozygous mean

Answer 17

When one of the inherited alleles is dominant and the other is recessive.

Question 18

what does genotpe mean

Answer 18

The combination of alleles an individual has, e.g. Aa

Question 19

What is embryonic screening

Answer 19

Embryonic screening allows scientists to observe whether the child will have a genetic condition or not. ● If the embryo is developed in the lab, cells can be taken from it and analysed ● DNA from embryos in the womb can also be extracted

Question 19

What does phenotype mean

Answer 19

The physical characteristics that are observed in the individual, e.g. eye colour

Question 20

What is Cystic fibrosis

Answer 20

disorder of the cell membranes, resulting in thick mucus in the airways and pancreas
● Caused by a recessive allele
● Both parents need to either be carriers (have one of the recessive alleles) or one must have CF themselves and the other is a carrier

Question 20

What does a single gene cross look at

Answer 20

A single gene cross looks at the probability of the offspring of two parents having certain genotypes and phenotypes.This is done using the alleles the two parents have for a gene and a Punnett square diagram.You should be able to draw and use a Punnett square diagram

Question 21

What is polydactyly

Answer 21

having extra fingers or toes
● Caused by a dominant allele

Question 21

What are genetic disorders caused by

Answer 21

by inheriting certain alleles
Some disorders are inherited. These disorders are caused by the
inheritance of certain alleles.

Question 22

What are the ethical for and against of embryonic screening

Answer 22

For-Reduces the number of people suffering (ethical).

Against- Could encourage people to pick characteristics - creating designer babies (ethical).

Question 23

What are the economic for and against of embryonic screening

Answer 23

For-Treating disorders is very expensive (economic).

Against-It is expensive to carry out screening (economic

Question 24

What are the social for and against of embryonic screening

Answer 24

For-There are many regulations in place to stop it getting out of hand (social).

Against-May promote prejudice as it suggests that those with genetic disorders will not live a full life or are unwanted (social).
Decisions about terminating a pregnancy have to be made (social).
The procedure can lead to a miscarriage (social).

Question 25

How many pairs of chromosomes does an ordinary human have and how many control characteristics and how many determine sex

Answer 25

23 pairs of chromosomes.
22 pairs control characteristics only, but one of the pairs carries the genes that determine sex.

Question 26

What sex chromosomes do males and females have

Answer 26

Females have two X chromosomes, so therefore only pass on X chromosomes in their eggs.
● Males have one X chromosome and one Y chromosome, so therefore can pass on X or Y chromosomes in their sperm.

Question 27

What can punnett squares/genetic cross be used to show

Answer 27

Punnett squares can be used to show sex inheritance

Question 28

What does variation depend on

Answer 28

Genotype: the genes it inherited
● Genes are passed on from the parent in sex cells.
● The combining of genes from the mother and father creates genetic variation.
● Only identical twins have the same genotype.
● There is lots of genetic variation in a population.

2. Environment: the place it lives in ● The conditions the organism grows and develops in also affects its appearance. ● Examples include scars in animals, or smaller and yellow leaves in plants.

3.combination of genetics and the environment, such as weight

Question 29

What effect does genetic variation have on phenotype

Answer 29

Most have no effect on phenotype.
● Some will influence phenotype but it is unlikely that it will bring about a new phenotype.
● If the mutation does determine the phenotype and it is advantageous, natural selection will mean it becomes the common phenotype relatively quickly.

most have no effect on the phenotype; some influence phenotype; very few determine phenotype.

Mutations occur continuously. Very rarely a mutation will lead to a new
phenotype. If the new phenotype is suited to an environmental change it
can lead to a relatively rapid change in the species

Question 30

What is evolution and the theory of evolution

Answer 30

Evolution is 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.

Theory of Evolution: All species have evolved from simple life forms that first developed more than three billion years ago.

Question 31

How does evolution occur

Answer 31

natural selection.
● Mutations occur which provide variation between organisms.
● If a mutation provides a survival advantage the organism is more likely to survive to breeding age.
● The mutation will then be passed onto offspring.
● Over many generations, the frequency of the mutation will increase within the population.

Question 32

What can evolution cause

Answer 32

one population of a species to become so different that they can no longer interbreed to produce fertile offspring. This means they have become a new species. This is called speciation

Question 33

What is selective breeding

Answer 33

Selective breeding is when humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic
This has been happening for many years since animals were domesticated and plants were grown for food.

Question 34

What is the process of selective breeding

Answer 34

Parents with desired characteristics are chosen.
● They are bred together.
● From the offspring those with desired characteristics are bred together.
● The process is repeated many times until all the offspring have the desired characteristic.

Question 35

What are characteristics in selective breeding chosen for

Answer 35

usefulness or appearance:
* Disease resistance in food crops.
* Animals which produce more meat or milk.
* Domestic dogs with a gentle nature.
* Large or unusual flowers.

Question 36

What are the problems with selective breeding

Answer 36

The problem is that it can lead to inbreeding.
● Breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals.
● This results in the reduction of the gene pool, as the number of different alleles reduce (as they mostly have the same alleles).
● This means if the environment changes or there is a new disease, the species could become extinct as they all have the same genetic make-up (so the chance of a few organisms having a survival advantage and not dying is reduced).
● Another problem is that the small gene pool leads to a greater chance of genetic defects being present in offspring, as recessive characteristics are more likely to present.

Question 37

What is genetic engineering

Answer 37

Genetic engineering: Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
● Plant cells have been engineered for disease resistance or to have larger fruits
● Bacterial cells have been engineered to produce substances useful to humans, such as human insulin to treat diabetes.
Sheep have been engineered so that they have drugs in their milk

Question 38

What is the process of genetic engineering

Answer 38

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.

Question 39

How does Genetic modification work in medicine

Answer 39

● It may be possible to use genetic engineering to cure inherited disorders. ● It is called gene therapy and involves transferring normal genes (not faulty) into patients so the correct proteins are produced

Question 40

How do GM crops work

Answer 40

Genetically modified crops ● They are engineered to be resistant to insects and to herbicides. ● This will result in increased yields as less crops will die.

Question 42

How does tissue culture work(cloning in plants)

Answer 42

Tissue culture: Important to preserve rare plant species or commercially in plant nurseries.
● Plant cells are taken
● They are placed in a growth medium with nutrients and hormones
● They grow into new plants, and are clones as they are genetically identical to the parent

Question 43

How does cuttings work (cloning in plants)

Answer 43

2. Cuttings: An older, easier method to produce clones ● Cuttings, such as a section of the stem, are taken from a plant with a desirable feature ● They are planted and produce clones as they are genetically identical to the paren

Question 44

How does embryo transplant work(cloning in animal)

Answer 44

Sperm cells and egg cells from parents with desirable features are obtained.
● In the lab, they are fertilised to form an embryo.
● The embryo divides many times and is then inserted into a host mother.
● The offspring which is eventually born is genetically identical (with the desirable feature) as they have genetic information from the same mother and father

Question 45

How does adult cell cloning work(cloning in animal)

Answer 45

Adult cell cloning
● The nucleus is removed from an unfertilised egg cell. ● The nucleus is removed from an adult body cell and placed in the denucleated egg cell.
● Through the stimulation of an electric shock, the egg cell begins to divide to form an embryo.
● The embryo is implanted into the womb of a female. ● The offspring born is a clone of the adult body cell.

Question 47

who put forward and What was the Theory of Evolution

Answer 47

Charles Darwin, proposed the theory of evolution by natural selection.
● Variation exists within species as a result of mutations in DNA
● Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully – called survival of the fittest.
● The beneficial characteristics are then passed on to the next generation
● Over many generations the frequency of alleles for this advantageous characteristic increase within the population

Question 48

Why was There was lots of controversy surrounding his ideas

Answer 48

There was lots of controversy surrounding his ideas for many reasons: 1. It contradicted the idea that God was the creator of all species on Earth. 2. There was not enough evidence at the time as few studies had been done on how organisms change over time. 3. The mechanism of inheritance and variation were not known at the time.

Question 49

What did Lamrack believe and how was it later prvoen wrong

Answer 49

Changes that occurred during the lifetime of an organism were passed onto offspring
● If an individual continually repeated an action, the characteristic that allowed it to do this would develop further
● For example, if a giraffe stretched to reach leaves on a tree high up, its neck would become longer allowing it to do this more easily. This characteristic would then be passed on to its offspring

Lamarck’s theory was proven wrong when it was understood that changes caused by the environment were not passed on in the sex cells.

Question 50

What is speciation

Answer 50

the process of a new species developing through the selection of different alleles. This increases the genetic variation until the new population cannot breed with those in the old population to produce fertile offspring.

Question 51

Who discovered th theory of speciation and what else did he do

Answer 51

Alfred Russel Wallace
developed the theory of speciation, and therefore evolution by natural selection.
● On his travels, he had the idea that the individuals who did not have characteristics to help them survive a change in the environment would die out.
● He published joint studies with Darwin.
● The publication of ‘On the Origin of Species’ meant Darwin received the credit for the theory.
● He continued to work across the world to collect evidence – one of his most important works was on warning colouration in animals
●Much more evidence over time has resulted in our current understanding

Question 52

What is the process of speciation

Answer 52

1.Variation exists within a population as a result of genetic mutations.
2. Alleles which provide a survival advantage are selected for through natural selection.
3. Populations of a species can become isolated, for example through physical barriers such as a rock fall preventing them from breeding together.
4. Different alleles may be advantageous in the new environment, leading to them being selected for.
5. Over time the selection of different alleles will increase the genetic variation between the two populations.
6. When they are no longer able to breed together to produce fertile offspring, a new species has formed

Question 53

What did Mendel do and what were his conclusions

Answer 53

He carried out breeding experiments on pea plants.
● He used smooth peas, wrinkled peas, green peas and yellow peas and observed the offspring to see which characteristics they had inherited
● Through keeping a record of everything he did and eventually publishing his work in 1866, he came to the conclusions that:
○ Offspring have some characteristics that their parents have because they inherit ‘hereditary units’ from each.
○ One unit is received from each parent.
○ Units can be dominant or recessive, and cannot be mixed together.

Question 54

why was the importance of Mendel’s discovery was not
recognised until after his death.

Answer 54

● In the late 19th century chromosomes as a part of cell division were observed
● In the 20th century, it was understood that chromosomes and units had similar behaviours. It was decided that units (now known as genes) were on the chromosomes.
● The structure of DNA was determined in 1953, which meant we were able to understand how genes worked.

Question 55

Why is the theory of evolution widely accepted

Answer 55

1. Fossils: the remains of organisms from many years ago, which are found in rocks
2. Antibiotic resistance in bacteria: the selection pressure of antibiotics leads to advantageous mutations being selected for in bacteria populations so they are no longer killed when exposed to antibiotics.

Question 56

What are fossils and what are the 3 ways theyre formed

Answer 56

Fossils are the remains of organisms from millions of years ago, which are found in rocks. They are formed from:
1. Parts of organisms that have not decayed because oxygen or moisture were not present, meaning that the microbes that cause decay cannot survive.
2. Parts of the organism such as teeth, shells and bones are replaced by minerals as they decay, forming a rock structure of the original part.
3. Preserved traces such as footprints, burrows and rootlet traces (the plants roots) remain due to the ground hardening around them and forming a cast.

Question 57

why can’t fossils be used to tell us how life started on Earth

Answer 57

because: ● Most early life forms are soft-bodied and therefore decay completely, so there are few fossils of them. ● Any traces left have been destroyed by geological activity.

Question 58

What is extinction and what factors cause it

Answer 58

when an entire species has died out

1. Changes in environment which the species cannot adapt fast enough to.
2. New predators may have evolved or migrated to the area.
3. A new disease arises and there are no resistant alleles to it.
4. They have to compete with a species which has advantageous mutations for the same food source.
5. A catastrophic event can wipe out a species.
6. Destruction of habitat

Question 59

What is bacteria resistance

Answer 59

Bacteria reproduce at a fast rate.
● Mutations during reproduction can result in new genes, such as the gene for antibiotic resistance. This the creation of a new strain.
● Exposure to antibiotics creates a selection pressure, as those with antibiotic resistant genes survive and those without die.
● As a result those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring.
● This population of antibiotic resistant bacteria increases.
● Bacterial diseases spreads rapidly because people are not immune to these new resistant bacteria and there is no treatment for it

Question 60

What is MRSA

Answer 60

Called a ‘superbug’ as it is resistant to many different types of antibiotics ●
Common in hospitals: spreads when doctors and nurses move to different patients

Question 61

How do you slow the development of resistance in bacteria:

Answer 61

1. Antibiotics should not be given for viral or non-serious infections
2. Specific antibiotics should be given for specific bacteria
3. Patients should complete their course of antibiotics – if they do not some bacteria may survive and mutate to become antibiotic resistant.
4. Antibiotics should be used less in agriculture – farmers currently use them to prevent their livestock dying from disease, but this overuse leads to antibiotic resistant bacteria which are then transferred to humans when they consume the meat.

Question 62

How to slow the transmission of the bacteria

Answer 62

1. Maintain high standards of hygiene in hospitals
2. Medical staff and visitors should wash hands regularly
3. Medical staff should wear disposable clothing or clothing that is regularly sterilised

Question 63

What is classification

Answer 63

Classification involves putting organisms into groups depending on their structure and characteristics.

Question 64

Who put forward the linnaean system and what were living things divided into

Answer 64

Carl Linnaeus put this forward in the 1700s ● Living things were divided into
kingdoms,
phylum,
class,
order,
family,
genus,
species

Question 65

What is the binomial system

Answer 65

first part is their genus and the second part is their species. An example is the ladybug, which has the name Harmonia (genus) axyridis (species).

Question 66

What are evolutionary trees

Answer 66

a method used by scientists to show how they
believe organisms are related. They use current classification data for
living organisms and fossil data for extinct organisms.

Question 67

What caused the 3 domain system

Answer 67

Developments in science such as the improvement of the microscope and increased knowledge of biochemistry (for example, RNA sequence analysis) found that some species were more distantly related than first thought

evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed, new models of classification were proposed.

Question 68

Who developed the 3 domain system and what were organisms divided into

Answer 68

Carl Woese added 3 larger groups above kind
organisms are divided into:
* archaea (primitive bacteria usually living in extreme environments)
* bacteria (true bacteria)
* eukaryota (which includes protists, fungi, plants and animals).