Transmission Genetics

Question 1

Who is known as the Father of modern genetics?

Answer 1

Gregor Mendel

Question 2

What is the difference between the blending hypothesis and the particulate hypothesis?

Answer 2

The blending hypothesis suggests genetic material blends together, while the particulate hypothesis states parents pass on discrete heritable units (genes).

Question 3

What is the term used for true-breeding parents in Mendel’s genetic crosses?

Answer 3

P1 or parental generation

Question 4

What generation do the offspring of the F1 generation produce?

Answer 4

F2 generation

Question 5

Fill in the blank: A heritable feature that varies among individuals is called a ______.

Answer 5

[character]

Question 6

What is an allele?

Answer 6

An alternative form of a single gene.

Question 7

What does the law of segregation state?

Answer 7

During gamete production, each egg or sperm cell receives just one of the two gene copies present in the organism, and the copy allocated to each gamete is random.

Question 8

What does phenotype refer to?

Answer 8

The physical expression of a trait.

Question 9

What is the ratio observed in the F2 generation of Mendel’s monohybrid crosses?

Answer 9

3:1 ratio

Question 10

What is the significance of a Punnett square?

Answer 10

It is a method for analysing genotypes and phenotypes resulting from the recombination of gametes during fertilisation.

Question 11

What is the genetic makeup of a homozygous individual?

Answer 11

Two like alleles for a gene.

Question 12

What is a heterozygous individual?

Answer 12

An individual with two different alleles for a gene.

Question 13

True or False: Mendel’s experiments were conducted without knowledge of chromosomes, genes, or gametes.

Answer 13

True

Question 14

What is the process called when two true-breeding varieties are mated?

Answer 14

Hybridization

Question 15

What does the term ‘true-breeding’ refer to?

Answer 15

Plants that produce offspring of the same variety when they self-pollinate.

Question 16

Fill in the blank: Mendel’s law of independent assortment states that genes for different traits are inherited ______.

Answer 16

[independently of one another]

Question 17

What is the educational method used to determine the possible combinations of traits in offspring?

Answer 17

Punnett squares

Question 18

What are the two types of alleles based on their dominance?

Answer 18

• Dominant allele
• Recessive allele

Question 19

What is the result of a monohybrid cross between two true-breeding parents with contrasting traits?

Answer 19

All F1 offspring display the dominant trait.

Question 20

What is the significance of Mendel’s postulates?

Answer 20

They explain the inheritance patterns observed in F2 offspring.

Question 21

What does ‘genotype’ refer to?

Answer 21

The genetic makeup of an individual.

Question 22

What is the expected phenotype ratio in the F2 generation from a monohybrid cross?

Answer 22

3:1 ratio

Question 23

What are gametes?

Answer 23

Reproductive cells that unite during sexual reproduction to form a new organism

Gametes include sperm and eggs

Question 24

What is the phenotype ratio of purple to white flowers in a typical Mendelian cross?

Answer 24

3:1

This ratio occurs when crossing heterozygous (Pp) plants

Question 25

What are the genotypes of purple flowers in pea plants?

Answer 25

* PP (homozygous) * Pp (heterozygous) ## Footnote Both genotypes produce purple flowers

Question 26

What is a test cross?

Answer 26

A method to determine the genotype of a plant with a dominant phenotype by crossing it with a homozygous recessive plant ## Footnote If any offspring display the recessive phenotype, the mystery parent must be heterozygous

Question 27

What is the potential result of a test cross if the unknown genotype is homozygous (SS)?

Answer 27

All offspring will be smooth heterozygotes (Ss) ## Footnote This indicates that the unknown parent was homozygous dominant

Question 28

What is the potential result of a test cross if the unknown genotype is heterozygous (Ss)?

Answer 28

Half of the offspring should be wrinkled homozygous recessives (ss) ## Footnote This indicates that the unknown parent was heterozygous

Question 29

What are some examples of single gene disorders?

Answer 29

* Sickle cell anaemia * Huntington disease * Cystic fibrosis * Tay-Sachs disease * Haemophilia * Thalassaemias * Phenylketonuria * Muscular dystrophies ## Footnote These disorders can be inherited recessively or dominantly

Question 30

What does Mendel's law of independent assortment state?

Answer 30

Each pair of alleles segregates independently of any other pair of alleles during gamete formation ## Footnote This principle was established through dihybrid crosses

Question 31

What is the phenotypic ratio expected from a dihybrid cross?

Answer 31

9:3:3:1 ## Footnote This ratio occurs when crossing two heterozygous parents for two traits

Question 32

What is epistasis?

Answer 32

When the alleles of one gene can mask the effects of the alleles of another gene ## Footnote This interaction affects the expression of traits

Question 33

What is incomplete dominance?

Answer 33

A genetic situation where the phenotype of the dominant allele doesn’t completely mask that of the recessive allele ## Footnote Results in a blending of parental traits

Question 34

What is codominance?

Answer 34

A genetic situation where both alleles are fully expressed in the phenotype ## Footnote This results in offspring displaying characteristics of both parental traits

Question 35

How many different gametes are produced in a dihybrid cross?

Answer 35

4 ## Footnote Calculated as 2 x 2 for two traits

Question 36

How many different gametes are produced in a trihybrid cross?

Answer 36

8 ## Footnote Calculated as 2 x 2 x 2 for three traits

Question 37

What is the genotype ratio from a monohybrid cross?

Answer 37

1:2:1 ## Footnote This ratio reflects the possible combinations of alleles in the offspring

Question 38

What is the phenotypic ratio from a monohybrid cross?

Answer 38

3:1 ## Footnote This ratio indicates the dominant to recessive phenotype ratio among offspring