DNA that carries the instructions for the order of amino acids in a protein.

How can a variant in coding DNA change a protein?

It can change an amino acid in the chain, which changes the way the protein folds and so alters its structure.

Explain how a mutation in coding DNA can stop an enzyme from working.

It changes the shape of the active site, so the substrate no longer fits and the reaction is not catalysed.

How can a variant in non-coding DNA affect the phenotype without changing the amino acids in any protein?

It alters how strongly a gene is expressed, so more or less of an otherwise normal protein is made.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Protein synthesis and the triplet code Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

Community Level Systems

Topic overview Cycling materials, and the role of microorganisms The carbon and water cycles, and decomposition Levels of organisation, and abiotic and biotic factors Interdependence, competition and trophic levels Pyramids of biomass and the efficiency of transfer

Genes, Inheritance and Selection

Topic overview Genetic terms, and the genome Genome, environment and mutations How genetic variants influence phenotype Asexual and sexual reproduction compared Haploid, diploid and meiosis Single gene inheritance and Punnett squares Sex determination, multiple genes and Mendel's work Variation within a population, and classification Natural selection and evolution Evidence for evolution, and the work of Darwin and Wallace

Global Challenges

Topic overview Field investigations, and human impact on ecosystems Maintaining biodiversity, and evidence for environmental change Food security, agricultural and biotechnological solutions Selective breeding and genetic engineering Health, disease, and types of disease Interactions between diseases, and how they spread Reducing the spread of disease, and named examples Physical and chemical plant defences Detecting plant disease; white blood cells and platelets Non-specific defences and the immune system Monoclonal antibodies and their uses Vaccines, medicines and aseptic technique Developing new medicines, and non-communicable disease Treating cardiovascular disease, and lifestyle factors Cancer, and the use of stem cells in medicine Gene technology in medicine, and the human genome

Organism Level Systems

Topic overview The nervous system and coordinated responses The reflex arc The eye and its common defects The structure and function of the brain Investigating and treating the brain Hormonal coordination, thyroxine and adrenaline Hormones in reproduction and the menstrual cycle Contraception and treating infertility Plant hormones and their commercial uses Homeostasis, and the skin in temperature control Insulin and glucagon in blood sugar control Type 1 and type 2 diabetes Osmotic changes in body fluids, and the kidneys The kidney tubule and the effect of ADH Responding to temperature and osmotic challenges

Scaling Up

Topic overview Diffusion, osmosis and active transport Mitosis, the cell cycle and cell differentiation Stem cells in animals and meristems in plants Surface area to volume ratio and exchange surfaces The circulatory system, the heart and blood vessels Red blood cells and plasma Root hair cells, transpiration and translocation Xylem and phloem Factors affecting water uptake, and the potometer

Genes, Inheritance and Selection

How genetic variants influence phenotype

3 things to know
Paper 4

Overview

The two ways a variant can change the phenotype, how a change in coding DNA alters a protein or an enzyme, and how a variant in non-coding DNA changes how much protein is made.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What are the two broad ways in which a genetic variant can influence the phenotype?

Key term

What is coding DNA?

Key term

What is non-coding DNA?

Questions from this subtopic

Each one with the model answer underneath.

1
What are the two broad ways in which a genetic variant can influence the phenotype?
Model answer
By altering the activity of a protein when the variant is in coding DNA, and by altering how genes are expressed when it is in non-coding DNA.
2
What is coding DNA?
Model answer
DNA that carries the instructions for the order of amino acids in a protein.
3
How can a variant in coding DNA change a protein?
Model answer
It can change an amino acid in the chain, which changes the way the protein folds and so alters its structure.
4
Explain how a mutation in coding DNA can stop an enzyme from working.
Model answer
It changes the shape of the active site, so the substrate no longer fits and the reaction is not catalysed.
5
What is non-coding DNA?
Model answer
DNA that does not code for a protein but can control whether nearby genes are switched on.
6
How can a variant in non-coding DNA affect the phenotype without changing the amino acids in any protein?
Model answer
It alters how strongly a gene is expressed, so more or less of an otherwise normal protein is made.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Algae and .

phytoplanktonfungianimals

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe blood becomes too dilute.

BLess ADH is released.

CThe collecting ducts become less permeable.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Egestion means passing out of undigested food as faeces.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Genes, Inheritance and Selection, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.