TOPIC 6 - INHERITANCE, VARIATION, EVOLUTION

What is a dominant allele?

An allele that is always expressed even if the other/ recessive allele is present

For CF, only 1 allelle in every 50 is the cystic fibrosis allele - explain why only 1 person in 2500 in the population has cystic fibrosis

CF is recessive so must have 2 CF allele; chance of 1 allele is 1/50 so chance of two 1/50 × 1/50 = 1/2500

Explain why the lack of FSH in the woman’s blood caused underdeveloped breasts

lack of FSH causes lack of oestrogen; breast development is dependent on oestrogen from follicles

Explain why the change in the no. chromosomes is important in meiosis

meiosis forms gametes; whichc fuse; so keeps the chromosome number constant/ prevents doubling in each generation/ gives correct chromosome numer

Describe how meiosis produces cells that are genetically different

random chromosomes from each pair/ move to one end of the cell/ goes into each new gamete

Give one piece of evidence which shows that MSUD is a recessive condition

Both parents without MSUD had a child with MSUD

Explain why the blood of a person with MSUD will have a high conc of toxic substance P

no enzyme 2 so can’t break down toxic substance; sub still made; diffuses move cells into blood

Explain why the blood of a person with MSUD will have a high conc of P in their urine

toxic sub passes through filter in kidney; some/all not reabsorbed back into blood

Explain why the person with MSUD has to have a low protein diet

proteins contain amino acids; so must keep amino acids in low count; so P does not build up in the body and cause damage to cells

Which part of the virus is put into the yeast cell?

gene

Which part of the virus is made by the yeast cell?

antigen

Give three factors that the weeds and crop plants compete for

• (sun)light

• water

• ions/minerals/salt

• oxygen in the soil

• space

Suggest one advantage of using glyphosate on fields where GM maize is growing

crop plants grow better/ have higher yield

Suggest one problem of using glyphosate on fields where GM maize is growing

• may kill/ harm/ poison other plants

• may pollute streams/ rivers/ soil

• may kill/ harm/ poison humans/ animals

Give possible reasons for extinction

• drought

• ice age

• global warming

• volcanic activity

• asteroid collision

• (new) predators

• (new) disease/ pathogen

• competition for food

• competition for mates

• lack of habitat or habitat change

Describe how selective breeding of wolves could produce a domestic animal that is less aggressive than the wolf

breed the least aggressive wolves; breed the least aggressive offspring

What is the name given to all of the organisms living in the same habitat?

Community

Ecosystem

The interaction between a community of living organisms (biotic factors) and their non-living (abiotic) environment in a specific area

Who invented the classification system?

Linnaeus

How are fossils formed?

The dead animal falls to the sea bed; it is buried in sediments; the soft parts of the animal decay; the remains that don’t decay are replaced by minerals

Explain how our understanding of evolution has developed due to fossil evidence + increased understanding of the mechanisms of genetics

Fossils:

• fossil show evidence of life in the past

• fossil show change over time

• fossil record shows development of species over time

• fossils show evidence of extinction

• fossil record shows how organisms from the past are related to species alive today

• gaps in fossil records are being filled in with new evidence

• ref to evolutionary trees

• description of how fossils are formed

Genetics:

• ref to Mendel’s breeding experiments with plants

• Mendel’s description/ idea of factors of inheritance

• dominant and recessive units/ alleles/ genes

• observation of chromosome behaviour during cell division

• chromosome behaviour and Mendel’s units work in similar ways

• structure of DNA worked out

• gene mechanism in determining protein synthesis work out

• genetic variation in species

• variation due to mutation or change in gene structure

• individuals with advantageous characteristics more likely to survive + reproduce

• survivors pass in advantageous alleles/ genes

• eg: of evolution (antibiotic resistance in bacteria)

• new species arise when sufficient changes occur to prevent successful reproduction

Biodiversity

The variety of species of organism in a place

Explain why through asexual reproduction, the offspring will inherit the same characteristic as the parent

no fusion of gamete/ mitosis; so offspring is genetically identical/ clone to parent plant

Give a reason why a mutation in the gene coding for haemoglobin could be harmful

could mean less oxygen for aerobic respiration

‘It is an advantage for people to have the HS allele in countries where malaria occurs.’ Evaluate the scientist’s statement

• HAH2 do no get malaria

• HAH2 survive sickle cell anaemia

BUT

• HAHA may die from malaria

• HSHS may severely become ill with sickle cell anaemia

• if parents HAHS then some offspring survive both malaria and sickcle cell or some offspring may become ill with malaria or sickle cell

What is an allele?

Different forms of a gamete

Suggest 1 way embryo screening can help people with a family history of a genetic disorder

• to help them prepare

• to inform whether to consider abortion

• to find out whether passed on disorder

shape of DNA

double; helix; long/thin

What part of DNA forms the code for a particular amino acid

Bases

Suggest 1 advantage of having DNA analysis

• to determine if the cancer is genetic

• to inform/ help treatment

• to allow embryo screening to ensure allele is not passed on

• to inform relative if they have inherited allele

• to detect cancer early before symptoms show

• to understand cause of the cancer

Why is DNA described as a polymer?

many joined nucleotides/ monomers

Describes the structure of a nucleotide

• phosphate

• attached to a sugar

• which has 1 of 4 bases attached

• based are A C G T

Describe how the non-coding parts of DNA can affect the expression of genes

non-coding parts can switch genes on/off

Give benefits of understanding the human genome

• diagnosis of inherited/ genetic disorder

• gene therapy or treatment of inherited disorders

• understanding human evolution or understanding ethnics origins or understanding ancestry

• tracing human migration patterns

Give a reason why several groups are scraped off the leaf with cloning plants

why nutrients are added to the agar jelly

why hormones are added to the agar jelly

why the plants are kept in sterile conditions

why the plant cells are kept at 20 degrees celsisus

• so many plants can be produced

• for making protein/ amino acids/ chlorophyll or for providing energy/ for respiration

• so differentiation occurs or so roots/shoots develop

• to prevent growth/ entry of microorganisms/ or to prevent decay

• so optimum/ good growth

Explain how a change in one amino acid in an enzyme molecule could stop the enzyme working

different protein made

active site changed

so substrate doesn’t not fit/ bind'

Explain why IVF was used for the cows instead of mating them naturally

takes less time; more offspring at the same time

The scientists will selectively breed some of the animls to make large volumes of low-fat milk - describe how

find female with the lowest fat in milk AND highest milk yielf; find male whose female offspring have highest milk yield AND lowest fat; cross the best for both features female with best male; select best offspring from each generation and repeat for several generations

Who wrote ‘On the origin of species’

Charles Darwin

Who worked on warning colouration in animals

Alfred Russel Wallace

Explain how the mutation could cause the enzyme not to work

there is a change in the three bases/ triplet

mutation changes the amino acid

this could change the protein

so it form a different shape with changed active sit

so enzyme no longer fits the substrate

What are stem cells?

• unspecialised/ undifferentiated cell that can divide and

• that can differentiate into other types of cells

why could it be useless to treat a genetic disease with their own tissue?

stem cells have same faulty gene/ allele

The range of beak depth on the islands differ - explain what might have caused this difference

• colonisers of Isabela have range of beak depths

• due to diff combo of alleles of several genes/ due to diff alleles of a gene/ due to mutations

• large range of seeds/ food on the island

• more competition for seeds/ food

• birds with larger beaks get enough food to survive and reproduce on Isabel

• survivors pass on beenficial alleles to offspring

Who develooped the 3-domain system of calssificaiton

Carl Woese

How can scientist swork out when an organism was alive

• comapre to other fossils of known age

• carbon dating

• by the age of the rock where fossil was found

Suggest how ancestors reached the islands across the ocean

carried by currents on masses of vegetation

Describe process of speciation

• isolation of different populations

• habitat variation between populations

• genetic variation or mutations

• better adapted sruvive and pass on favourable alleles to offspring

• eventually can’t produce fertile offspring with other populations

What is a fossil

remains of an organism

from a long time ago

Give reasons why the fossil record is not clear for older species

• fossils buried deeper so harder to find

• fossils smaller so harder to find

• more likely to be destoryed by geological activity/ erosion/ earthquakes

• oldest orgs were soft-bodies so most decayed

• dating older fossils is harder

• older eras less reserached by scientists because less to find

• unclear when one species evolves into another species because not enough fossils found

‘The data in Figure 2 shows that humans caused mass extinctions.’ Evaluate the student’s statement.

SUPPORT:

• decrease in mammals is larger in some area

• decrease occurs when humans enter those areas

• decrease occurs at different imes in the areas so doesn’t suggest a worldwide climate change

• decrease is not always immediate, suggesting human population grew and then impacted

NOT SUPPORT:

• only shows large mammals not other species

• correlation doesn’t mean causation

• there were always some left so wasn’t ‘mass extinction’

• decrease could have been caused by other factors

• no informationa about abiotic factors/ climate change/ predators/ pathogens/ food sources

• decrease in Africa is much smallers

• decrease in Madagascar was gradual

• only show data for four areas of world not other areas

Advantage + Disadvantage of mass extinction

A: allows evolution of new species

D: loss of potential, future biodiversity, reduction in range of alleles

How could cutting trees down in a mixed way help biodiversity?

• displaced animals can move to adjacent areas

• to find food/ shelter where trees haven’t been cut

• seeds return to deforest area from other forested area

• so the plants being to grow back to provide food and shelter for naimals again

• animals can return to re-growing area

• sufficient time for regenration

• old growth area is a source of recolonising organisms

Describe how fish fossils are formed

fish dies buried in sediments/ sand/ mud

only soft aprts decays or hart parts not decay/ eaten

mineralisation occurs

Describe the process of natural selection

• variation

• better adapted survive

• reproduce and pass on favourable alleles

How to prove breeds are part of the same species

• interbreeding successful produces fertile offspring

Explain why they became different breeds not diff. species

• continued to mate with one another

• few beneficial mutation

• similar condition on each island so similar adaptations/ feature fit

Give the reason why the gene for a hormone released in the brain doesn’t have to taken from cells in the brain

white blood cells have the same DNA/ same gene

WHy can enzyme 1 cut the gene for A but not the gene for B

the enzyme’s structure has a specifically shaped active site

and the B genes have different sequence of bases

so only A gene fits the active of enzyme 1/ is complementary

Suggest reasons why people might selectively breed cats

• so don’t cause allergies in people

• so that they don’t have genetic defect

• to be docile cat

• for aesthetic reasons

what’s the problem with interbreeding

more likely to pass on recessive disorder

more likely to be susceptible to diseases

What is the advantage of modern day horses feet to the past

large surface area in contact with the ground

so less pressure on the ground

so could run fast

less likely to sink into mud