Patterns Of Inheritance

Question 1

What is the difference between continuous and discontinuous variation?

Answer 1

Continuous: no distinct categories e.g height

Inherited characteristics that show continuous variation are usually influenced by many genes (poly genic)

Discontinuous: distinct categories e.g blood group

Usually just one gene

Question 2

How do genes influence variation?

Answer 2

Individuals of the same species may have the same genes but different alleles.

Genes and alleles make up their genotype

Sexual reproduction leads to variation in genotypes within a species:

meiosis makes gametes with a unique assortment of alleles through crossing over and the independent assortment of chromosomes

The random fusion of gametes during fertilisation increase genetic variation

Differences in genotypes within a result in variation in phenotype

Question 3

How does the environment create variation?

Answer 3

Differences in the environment e.g food, climate , lifestyle

Characteristics controlled by environmental factors can change over an organisms life

E.g chlorosis: when plants dont produce enough chlorophyll and turns yellow (caused by lack of magnesium)

Question 4

Explain and give an example of how both genetics and environment can influence variation.

Answer 4

Genetic factors determine genotypes and the characteristics an organism is born with but environmental factors can influence how some characteristics develop.

E.g
Body mass in animals
Partially genetic but also strong influence by diet and lifestyle

Question 5

What is a monogenic cross?

Answer 5

A genetic cross that studies the inheritance of one characteristic, controlled by one gene

E.g genes with two alleles
The dominant allele is represented with a dominant letter and restive is represent with lowercase. 2 alleles for gene found at same gene locus on homologous chromosone

Answer 7

A genetic cross that studies the inheritance of one characteristic, controlled by one gene

E.g genes with two alleles
The dominant allele is represented with a dominant letter and restive is represent with lowercase. 2 alleles for gene found at same gene locus on homologous chromosome

Question 8

What is a Mendelian ratio?

Answer 8

A pattern of inheritance in which the ratio of phenotypes from a genetic cross can be [predicted using Mendelssohn principles.

E.g
- a genetic cross of a homozygous dominant organism with a homozygous recessive organism produces all heterozygous
- a genetic cross of two heterozygous produces a ratio of 3 offspring w dominant and 1 w respective characteristic

Question 10

What’s is codominance

Answer 10

When both alleles are expressed in the heterozygous neither is dominant or recessive