4.) Topic 4 a: Variation

Question 1

What is variation?

Answer 1

The differences between individuals of the same species

Question 2

What are the 2 things variation can be due to?

Answer 2

Genetics

Environmental

Question 3

What are the 2 types of variation?

Answer 3

Continuous

Discontinuous

Question 4

What does it mean by continuous variation?

Give 2 examples

Answer 4

Produces characteristics which do not fall into distinct categories, instead showing a continuous range e.g. weight and height

Question 5

What does it mean by discontinuous variation?

Give 4 examples

Answer 5

Produces characteristics that fall into distinct categories e.g. gender, eye, colour, blood group

Question 6

What is genetic variation?

Answer 6

Variation in the genotypes of organisms of the same species due to the presence of different alleles

Created differences in phenotypes

Question 7

What is environmental variation?

Answer 7

Variations in phenotype that are acquired during the lifespan of an organism e.g. diet, lifestyle, climate, exposure to light

Question 8

What created genetic variation in a species?

Answer 8

sexual reproduction

spontaneous mutations

Question 9

How does sexual reproduction create variation?

Answer 9

Meiosis produces genetically different gametes(haploid)

During fertilization, one gamete from each parent fuses to form a zygote(diploid)

Genetic information from both parents is mixed to form a unique individual

Question 10

Does asexual reproduction create genetic variation and why?

Answer 10

No because it involves mitosis which produces 2 genetically identical daughter cells known as clones

Question 11

What is the definition of mutation?

Answer 11

A random change to the base sequence in DNA which results in genetic variants

Question 12

How may a gene mutation affect an organism’s phenotype (3)

Answer 12

Neutral mutation does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype

Mutation may cause a minor change in an organism’s phenotype e.g. change in eye colour

Mutation may completely change the sequence of amino acids. This may result in a non-functional protein. Severe changes to phenotype.

Question 13

What substance increases the mutation rate of DNA?

Answer 13

Mutagens e.g. ionising radiation

Question 14

How can mutations cause genetic conditions passed on in families
Give an example

Answer 14

Mutations result in a harmful allele
Allele inherited by offspring
E.g. recessive allele is cystic fibrosis

Question 15

What are 2 ways in which inheritance can be illustrated?

Answer 15

Punnett squares

Family tree

Question 16

What is cystic fibrosis? [2]

What is the genotype of this

Answer 16

A recessive condition resulting in the production of a sticky mucus that affects the lungs and digestive system

Homozygous recessive (ff)

Question 17

What is gene therapy?

Answer 17

A number of techniques used to counteract the effects of a defective allele within DNA

Question 18

What are the types of gene therapy

Answer 18

Insertion of a functional allele into DNA which replaces the faulty allele. A healthy dominant allele can counteract the recessive faulty allele

‘Switching off’ the faulty allele

Question 19

Describe the ethical issues surrounding gene therapy?

Answer 19

Expensive - money could be better invested elsewhere

Religious groups do not agree with genetic manipulation

Health implications - new gene may produce an immune response