Genetics

Question 1

Define genetics

Answer 1

The study of how genetic characteristics are passed down from parents to the child

Question 2

Define genus locus

Answer 2

The exact position of a gene on a chromosome

Question 3

Define allele

Answer 3

Different forms of a gene which occur in the same locus on homologous chromosomes

Question 4

Mendel’s Law of Dominance

Answer 4

When two homozygous organisms with contrasting characteristics are crossed, all the individuals of the F1 generation will display the dominant trait
An individual that is heterozygous for a particular characteristic will have the dominant trait as the phenotype

Question 5

Define genotype

Answer 5

The genetic composition of an individual

Question 6

Define phenotype

Answer 6

The physical appearance of an organism based on the genotype and the environment; how the genes are expressed in that individual

Question 7

Define homozygous

Answer 7

Two alleles for a characteristic are the same

Question 8

Define heterozygous

Answer 8

Two alleles for a characteristic are different

Question 9

What is the dominant allele?

Answer 9

An allele that is expressed in the phenotype when found in both heterozygous (Tt) and homozygous (TT) conditions

Question 10

What is the recessive allele?

Answer 10

An allele that is masked in the phenotype when found in heterozygous (Tt) conditions and only expressed in homozygous (tt) conditions

Question 11

Mendel’s Principle of Segregation

Answer 11

An organism possesses two factors (alleles) which separate/segregate so that each gamete contains only one of these factors (alleles)
Half the gametes carry one allele and the other half carry the other allele

Question 12

Mendel’s Principle of Independent Assortment

Answer 12

The various ‘factors’ controlling different characteristics are separate entities, not influencing each other in any way, and sorting themselves out independently during gamete formation
(The allele a gamete receives for one gene does not influence the allele received for another gene)

Question 13

Complete dominance

Answer 13

The dominant allele completely masks expression of the recessive allele in heterozygous conditions

Question 14

Incomplete dominance

Answer 14

Neither one of the two alleles of a gene is dominant over the other, resulting in an intermediate phenotype in heterozygous conditions

Question 15

Co-dominance

Answer 15

Both alleles are expressed equally in the phenotype (patchy cow example)

Question 16

Multiple alleles

Answer 16

Genes which have more than two alternatives at the same locus

Question 17

What type of dominance is seen in inheritance of blood groups

Answer 17

Partly co-dominance and partly complete dominance

Question 18

Define polygenic characteristics

Answer 18

Characteristics which are the result of multiple genes

Question 19

What are gonosomes?

Answer 19

X and Y sex chromosomes

Question 20

What are sex-linked genes?

Answer 20

Genes carried by the gonosomes

Question 21

Is the allele for colour-blindness dominant or recessive?

Answer 21

Recessive

Question 22

On which sex chromosome, X or Y, is colour-blindness carried?

Answer 22

X chromosome

Question 23

Is the allele for haemophilia dominant or recessive?

Answer 23

Recessive

Question 24

On which sex chromosome, X or Y, is haemophilia carried?

Answer 24

X chromosome

Question 25

What is a mutation?

Answer 25

A permanent change to the DNA of a cell

Question 26

The two types of mutations

Answer 26

Gene mutations and chromosomal mutations

Question 27

What is the function of a pedigree diagram?

Answer 27

Used to study/trace the inheritance of a characteristic over many generations