Patterns of inheritance

Question 1

What’s a gene?

Answer 1

A sequence of bases on a DNA molecule that codes for a protein that results in a characteristic

Question 2

What’s a base?

Answer 2

A nitrogen- containing molecule that forms part of a DNA nucleotide

Question 3

What are alleles?

Answer 3

One or more versions of the same gene

e.g., B = brown eyes, b = blue eyes

Question 4

How many alleles of each gene do plants and animals tend to have?

Answer 4

2 alleles of each gene (one from each parent)

Question 5

What’s a locus?

Answer 5

The fixed position of an allele on each chromosome in a pair

Question 6

What’s the genotype?

Answer 6

The alleles an organism has

Question 7

What’s the phenotype?

Answer 7

The characteristics the alleles produce in an organism

(can’t always be seen e.g., metabolic rate)

Question 8

What are codominant alleles?

Answer 8

When both alleles are expressed in a phenotype because neither one is recessive

Question 9

How many alleles are there for each gene?

Answer 9

2

Question 10

How many alleles for each gene do gametes (sex cells) have?

Answer 10

1

Question 11

What’s monogenic inheritance?

Answer 11

Inheritance of a characteristic controlled by a single gene

Question 12

What’s the phenotypic ratio?

Answer 12

The ratio of different phenotypes in the offspring

Question 13

What’s the definition of a population?

Answer 13

A group of organisms of the same species living in a particular area

Question 14

What’s a selection pressure?

Answer 14

Anything that affects an organisms chance of survival

Question 15

What’s a gene pool?

Answer 15

The complete range of alleles present in a population

Question 16

What’s the allele frequency?

Answer 16

How often an allele occurs in a population

Question 17

What’s stabalising selection?

Answer 17

Environment is stable and individuals with alleles towards middle range more likely to survive

Question 18

What’s directional selection?

Answer 18

Environment is changing and individuals with alleles of an extreme type are more likely to survive

Question 19

What’s the difference between natural selection and genetic drift?

Answer 19

• Natural selection - characteristics become more common if they increase organism’s chance of survival
• Genetic drift - characteristics become more common by chance

Question 20

What’s a genetic bottleneck?

Answer 20

An event that causes a big reduction in population size, leading to reduction in gene pool

e.e.g, disease/ habitat destruction

Question 21

What’s the founder effect?

Answer 21

When a few organisms from a population start a new population