Chapter 20 Patterns Of Inheritance And Variation

Question 1

What is a genotype?

Answer 1

The combination of alleles an organism inherits for a characteristic

Question 2

What is a phenotype?

Answer 2

The physical appearance of an organism which can be affected by the environment

Question 3

What factors can affect variation?

Answer 3

Genetics
Environment

Question 4

Describe what factors can affect Chlorosis in plants

Answer 4

Environmental factors
-Lack of light
-Mineral deficiencies (lacking Fe or Mg which are involved in chlorophyll production)
-Viral infections (interfere with the metabolism of cells)
Genetics
-Genes control the production of Chlorophyll

Question 5

Describe the factors that can affect animal body mass

Answer 5

Environmental
-Quantity and quality of food eaten
-Amount of exercise
-Presence of disease

Genetics
-Mutations can result in alterations in fat deposition

Question 6

What is an allele?

Answer 6

Different forms of the same gene

Question 7

What are Phenotypical modifications?

Answer 7

Any changes that the environment makes to an individuals physical appearance are known as modifications.

Question 8

What is a dominant allele?

Answer 8

Version of a gene that will always be expressed if present in an organism.

Question 9

What is a recessive allele?

Answer 9

Version of the gene that is only expressed if two copies of this allele are present in an organism.

Question 10

What is a Homozygous allele?

Answer 10

Two identical alleles for a characteristic
-Dominant or Recessive

Question 11

What is a Heterozygous allele?

Answer 11

Two different alleles for a characteristic

Question 12

What is Continuous variation?

Answer 12

A characteristic that can take any value within a range of
Eg, skin colour, height

Question 13

What is Discontinuous variation?

Answer 13

A characteristic that can only appear in specific (discrete) values
Eg, blood group, eye colour

Question 14

What is the cause of continuous variation?

Answer 14

Genes and the environment

Question 15

What is the cause of discontinuous variation?

Answer 15

Genetic

Question 16

How is continuous variation controlled?

Answer 16

Controlled by a number of genes

Question 17

How is discontinuous variation controlled?

Answer 17

Controlled by one or two genes

Question 18

What is Monogenic inheritance?

Answer 18

A characteristic inherited on a single gene

Question 19

Describe the steps required when interpreting genetic crosses

Answer 19

1- State the genotype of both parents
2- State the gametes of each parent
3- Use a punnet square to show the results of the random fusion of gametes during fertilisation
4-State the proportion of each genotype produced using a percentage or ratio
5- State the corresponding phenotype of each possible phenotypes

Question 20

What is Codominance?

Answer 20

When different alleles of a gene are equally dominant and both are expressed in the phenotype.

Question 21

How are codominance alleles represented?

Answer 21

A letter is chosen to represent the gene.
Eg, ‘C’ for colour of flowers
The different alleles are represented using a second letter which is shown as a superscript.
Eg, C^R = allele codes for red flowers
C^W = allele codes for white flowers

Question 22

What are Multiple alleles?

Answer 22

A gene with more than two possible alleles

Question 23

What is an autosomal gene?

Answer 23

A specific gene not on a sex chromosome