Inheritance

Question 1

What is a chromosome?

Answer 1

Chromosomes are thread-like structures in the nucleus of a cell that contain genetic information

Each chromosome includes a long molecule of DNA and contains multiple genes.

Question 2

What is the structure of DNA?

Answer 2

A DNA molecule consists of two long strands twisted in a double helix, made of nucleotides

Each nucleotide contains a sugar, a base, and a phosphate group.

Question 3

What are the four types of bases in DNA?

Answer 3

• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)

Question 4

What is a gene?

Answer 4

A gene is the basic unit of inheritance, a short length of DNA that codes for a specific protein.

Question 5

What determines the protein formed by a gene?

Answer 5

The sequence of bases in the gene determines the sequence of amino acids in the protein.

Question 6

What is inheritance?

Answer 6

Inheritance is the transmission of genetic information from generation to generation.

Question 7

Define allele.

Answer 7

An allele is an alternative form of a gene responsible for determining contrasting characteristics for a trait.

Question 8

What is a homozygous condition?

Answer 8

A condition where an organism possesses 2 identical alleles for a characteristic (e.g., RR or rr).

Question 9

What does pure breed refer to?

Answer 9

An organism that is homozygous for one or more traits.

Question 10

Define heterozygous.

Answer 10

An organism that contains 2 different alleles for one character/trait (e.g., Rr).

Question 11

What is genotype?

Answer 11

The genetic constitution of an organism with respect to the alleles under consideration (e.g., RR, Rr, rr).

Question 12

What is phenotype?

Answer 12

The observable characteristic of an organism resulting from both genes and environmental effects.

Question 13

What is a dominant allele?

Answer 13

An allele that can express itself in the phenotype in both homozygous and heterozygous conditions.

Question 14

What is a recessive allele?

Answer 14

An allele that can express itself in the phenotype only in the homozygous condition.

Question 15

What are homologous chromosomes?

Answer 15

Chromosomes that have the same length, shape, and carry alleles for the same characteristics.

Question 16

What is the role of gametes in inheritance?

Answer 16

Gametes transfer genes from parent to offspring.

Question 17

Why are garden peas used in genetics experiments?

Answer 17

They have contrasting characteristics, are bisexual, easy to grow, and have a short generation time.

Question 18

What is monohybrid inheritance?

Answer 18

The inheritance of one character that has 2 contrasting forms.

Question 19

What is the F2 ratio in monohybrid inheritance?

Answer 19

The F2 generation consists of plants with round and wrinkled seeds in a ratio of 3:1.

Question 20

What is a test cross?

Answer 20

A cross between an organism showing the dominant phenotype and one showing the recessive phenotype to determine the unknown genotype.

Question 21

What is co-dominance?

Answer 21

A condition where alleles express themselves equally in the heterozygous condition, resulting in an intermediate phenotype.

Question 22

Define multiple alleles.

Answer 22

A condition where a gene exists in more than 2 alternative forms for determining a character.

Question 23

What are the sex chromosomes in humans?

Answer 23

The sex chromosomes are X and Y, with XX for females and XY for males.

Question 24

What is a mutation?

Answer 24

A sudden drastic change in the structure or amount of DNA in a cell that may have phenotypic effects.

Question 25

What causes mutations?

Answer 25

Exposure to mutagens such as X-rays, chemicals, and radiation.

Question 26

What is albinism?

Answer 26

A genetic condition caused by a mutation that results in the absence of pigment in skin and hair.

Question 27

What is albinism an example of?

Answer 27

Gene mutation ## Footnote Albinism results from a mutation where the normal allele (A) causes normal pigment, and the mutant allele (a) causes absence of pigment.

Question 28

What genotypes have pigment in skin, hair, choroid, and iris?

Answer 28

AA and Aa ## Footnote Individuals with these genotypes exhibit normal pigmentation.

Question 29

What genotype do albino individuals have?

Answer 29

aa ## Footnote Individuals with this genotype lack pigment in skin, hair, choroid, and iris.

Question 30

What is the phenotypic ratio of a cross between two Aa parents regarding albinism?

Answer 30

3:1 ## Footnote This ratio indicates three normal offspring for every albino offspring.

Question 31

What is sickle cell anaemia an example of?

Answer 31

Gene mutation ## Footnote Sickle cell anaemia results from a mutation affecting hemoglobin production.

Question 32

What genotype represents individuals with normal hemoglobin?

Answer 32

SS ## Footnote These individuals have normal biconcave red blood cells.

Question 33

Which genotype results in acute anaemia due to sickle-shaped red blood cells?

Answer 33

ss ## Footnote Individuals with this genotype have abnormal hemoglobin and often die early.

Question 34

What is chromosomal mutation?

Answer 34

A change in the structure or number of chromosomes in a cell ## Footnote An example is Down's syndrome.

Question 35

What chromosome number is characteristic of Down's syndrome?

Answer 35

47 ## Footnote Individuals with Down's syndrome have an extra copy of the 21st chromosome.

Question 36

What is the significance of mutations?

Answer 36

They lead to variation in a species ## Footnote Mutations, meiosis, random mating, and random fertilization contribute to genetic variation.

Question 37

What are the two types of variation?

Answer 37

* Continuous variation * Discontinuous variation ## Footnote These types refer to how characteristics differ among individuals in a species.

Question 38

Define continuous variation.

Answer 38

Variation where differences are not clear cut and show a gradual transition ## Footnote Examples include height and skin color.

Question 39

What causes continuous variation?

Answer 39

* Controlled by many genes * Influenced by environmental factors ## Footnote Characteristics like height and skin color are examples.

Question 40

Define discontinuous variation.

Answer 40

Variation where characteristics show clear-cut differences ## Footnote Examples include blood type and eye color.

Question 41

What causes discontinuous variation?

Answer 41

Controlled by few genes, usually one, and not influenced by environmental factors ## Footnote Blood groups serve as an example.

Question 42

What is selection in biological terms?

Answer 42

A process allowing certain forms of a species to survive and reproduce ## Footnote This can be natural or artificial selection.

Question 43

What is natural selection?

Answer 43

Nature allows the best-adapted forms to survive and reproduce ## Footnote It ensures the survival of species over time.

Question 44

What are the principles of natural selection?

Answer 44

* Overproduction of offspring * Struggle for survival * Variation within populations * Survival of the fittest ## Footnote These principles explain how natural selection operates.

Question 45

What is industrial melanism?

Answer 45

The phenomenon where darker forms of species become more prevalent due to environmental changes ## Footnote Example: The peppered moth in industrialized areas.

Question 46

What is artificial selection?

Answer 46

Man allows forms with beneficial characteristics to survive and reproduce ## Footnote This is also known as selective breeding.

Question 47

What are examples of artificial selection?

Answer 47

* High-yield dairy cows * Disease-resistant wheat * Rice varieties tolerant to low oxygen ## Footnote These examples illustrate human intervention in breeding.

Question 48

What is evolution?

Answer 48

Gradual changes over millions of years that lead to new species ## Footnote Charles Darwin proposed the theory of evolution by natural selection.

Question 49

How does evolution occur?

Answer 49

Through reproduction, mutations, and selection of favorable characteristics ## Footnote Over generations, these traits accumulate, leading to new species.