Patterns of inheritance

Question 2

Homologous chromosomes

Answer 2

1. Same length
2. Same position of centromere
3. Carries the same sequence of genes in the same locus (position)

Question 3

Genotype

Answer 3

The genetic constitution of an organism. The combination of alleles found at the same gene locus of homologous chromosomes.

Question 4

Genotype examples

Answer 4

TT and tt

Question 5

Phenotype

Answer 5

The physical & chemical characteristics that make up the appearance of an organism is known as its phenotype.
It is determined by an interaction between genes & the environment

Question 6

Phenotype examples:

Answer 6

Color of flower
Shape of nose
Size of olive

Question 7

Phenotype example: gene and environment

Answer 7

Genes, soil nutrients and sunlight

Question 8

Gene

Answer 8

A sequence of bases on DNA that codes for a single polypeptide chain.

Question 9

Gene locus

Answer 9

The gene locus is the location of a gene on the chromosome

Question 10

Allele

Answer 10

These are alternate forms of a gene found at a particular gene locus. They differ from each other in the sequence of bases

Question 11

Allele examples:

Answer 11

Eye color
Hair color

Question 12

The alleles are written:

Answer 12

A = Dominant allele for normal leaves
a = recessive allele for disease-like lesions
AA (normal) Aa (normal) aa (lesion)

Question 13

Dominant allele

Answer 13

The allele which expresses itself in the phenotype, both in homozygous & heterozygous genotype

Question 14

Recessive allele

Answer 14

Recessive allele is an alternative form of a gene that is only expressed in individual homozygous for the allele

Question 15

Recessive allele example:

Answer 15

aa

Question 16

Homozygote

Answer 16

If both alleles that code for characteristics are identical, then the individual is homozygous for that characteristic & is called a homozygote (‘homo’ means ‘the same’)

Question 17

Homozygote examples

Answer 17

aa and AA

Answer 18

Homozygote are also referred to as true breeding
Because if two individuals that are homozygous for the same characteristics are crossed, all the offsprings of all the generations that follow will show the same characteristics in their phenotype (unless a mutation occurs)

Question 19

Heterozygote

Answer 19

If the two Allie’s coding for a characteristics are different, the individual is heterozygous for that characteristic & is called heterozygote ( ‘hetero’ means different), & they are not true breeding

Question 20

Heterozygote example

Answer 20

Aa

Question 21

Monohybrid cross

Answer 21

It is a cross between two organisms involving on trait

Question 22

Test cross

Answer 22

Test crosses are used to test an individuals genotype by crossing it with an individual of a known genotype

Question 23

Test cross: why is it done

Answer 23

To find if an organism is homozygous dominant or heterozygous

Question 24

Test cross: how is it done

Answer 24

Organism of unknown genotype is mated with a homogeneous recessive one

Question 25

Codominance

Answer 25

Codominance is a condition in which both alleles of a gene are expressed in heterozygous offspring

Question 28

Genetic experiments

Answer 28

It is unethical to use humans as experimental organisms. So for these experiments they use certain organism. Such as drosophila, pea plant, e-coli and aspergillus These organisms are relatively easy & cheap to grow to chances of successful breeding & minimise experimental costs Have a short life cycle so that the results of crosses &/or mutations can be seen quickly a Produce large numbers of offspring so that the results of any crosses are statistically relevant