Inheritance

Question 1

Define a gene

Answer 1

A gene is a unit of inheritance with a specific sequence of nucleotides as part of a DNA molecule containing information to synthesise a polypeptide

Question 2

Define an allele

Answer 2

An allele is an alternative form of a gene

Question 2

What is a dominant allele

Answer 2

An allele that can always be expressed in the phenotype

Question 3

What is homozygous dominant

Answer 3

Having 2 identical dominant alleles

Question 3

What is heterozygous

Answer 3

Having 2 different alleles

Question 3

What is a recessive allele

Answer 3

An allele that can be expressed in the phenotype when it is homozygous

Question 4

What is homozygous recessive

Answer 4

Having 2 identical recessive alleles

Question 5

Define genotype

Answer 5

Genotype is the genetic makeup of an organism

Question 6

Define phenotype

Answer 6

Phenotype is an observable trait of an organism

Question 7

Define codominance

Answer 7

Codominance is when both alleles have equal effect on the offspring, so both alleles are expressed in the phenotype

Question 7

Define monohybrid inheritance

Answer 7

Monohybrid inheritance is the inheritance of a single characteristic

Question 7

How is genotype linked to phenotype

Answer 7

Phenotype is the expression of the genotype in a tangible form

Question 8

What is Mendel’s Law of Segregation

Answer 8

Mendel’s Law of Segregation states that genes occur in pairs and that each gamete only receives 1 allele of each pair, so the 2 alleles of the organism are separated into different gametes to ensure variation

Question 9

What are male sex chromosomes

Answer 9

XY

Question 10

What are female sex chromosomes

Answer 10

XX

Question 11

Define sex linkage

Answer 11

Sex linkage is the carrying of genes on sex chromosomes

Question 12

In a pedigree, what are males and females represented by

Answer 12

Male - square
Female - circle

Question 13

What are autosomes

Answer 13

Homologous chromosomes except sex chromosomes

Question 14

Define variation

Answer 14

Variation is the differences in traits between individuals of the same species

Question 15

What types are variation are there

Answer 15

• Continuous variation
• Discontinuous variation

Question 16

What are some causes of variation

Answer 16

Genetic factors
- Chromosome and gene mutation
- Random fertilisation of gametes

Environmental factors

Question 17

Describe continuous variation

Answer 17

• Range of phenotypes
• Greatly affected by environmental conditions
• Controlled by many genes

Question 18

Describe discontinuous variation

Answer 18

• A few clear-cut phenotypes
• Relatively unaffected by environmental conditions
• Controlled by just 1 or a few genes

Question 18

Define evolution

Answer 18

Evolution is the change in heritable characteristics of biological populations over successive generations

Question 18

What is Darmin’s theory of evolution

Answer 18

Darwin’s theory of evolution states that all organisms arise and develop through natural selection

Question 19

What are the principles of natural selection

Answer 19

• Variation
• Heredity
• Overproduction
• Limited resources
• Fitness
• Genetic composition

Question 20

Describe how natural selection works

Answer 20

• Variation within population caused by spontaneous mutation
• Only fittest will survive
• Those with genetic variation best adapted to environment more likely to survive till maturity
• Higher chance of reproducing and passing down desirable genes to offspring

Question 21

What are some environmental factors that act as forces of natural selection

Answer 21

• Amount of water and food
• Living space