levo

Genetics

Causes of variation: genes and environment

  • 3 things to know
  • Paper 1

Overview

Characteristics controlled by many genes such as height and their continuous range, genetic variation from mutation and sexual reproduction, acquired characteristics and environmental variation, identical twins, and presenting variation with frequency tables, histograms, bar charts and the modal class.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Give an example of a human characteristic that is controlled by many genes.

Key term

Explain why a simple genetic cross diagram cannot predict a person's height.

Key term

Explain why brothers and sisters vary so widely in characteristics such as skin colour.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Are most features of an organism's phenotype controlled by a single gene?

    Model answer

    No, most phenotypic features are the result of several genes acting together.

  2. 2

    Give an example of a human characteristic that is controlled by many genes.

    Model answer

    Height is controlled by many genes.

  3. 3

    Explain why a simple genetic cross diagram cannot predict a person's height.

    Model answer

    Height is controlled by many genes rather than one, so a single pair of alleles does not decide it.

  4. 4

    Describe the range of values seen for a characteristic controlled by many genes.

    Model answer

    It shows a continuous range of values between two extremes rather than a few separate categories.

  5. 5

    Explain why brothers and sisters vary so widely in characteristics such as skin colour.

    Model answer

    Many genes contribute, and each child inherits a different combination of alleles from those genes.

  6. 6

    Name the two causes of variation that influence phenotype.

    Model answer

    Genetic variation and environmental variation.

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.

Key Concepts in Biology
Cells and Control
Genetics
Natural Selection and Genetic Modification

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.

Type 2 .
diabetescancercholera

Blank Blitz makes facts automatic

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

ANitrates cause an algal bloom that blocks the light.
BWater plants die and decay.
CThe decomposers use up the dissolved oxygen.

Build It gets the exam shape right

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

A millimetre is 10⁻³ of a metre.
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 Genetics, 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.

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