2B2 Basic Principles of Genetics

Question 1

What is genetics?

Answer 1

The study of genes and DNA.

Question 2

Who was Gregor Mendel and what was his contribution to genetics?

Answer 2

• He was a 19th-century Austrian monk and scientist.
• His research on the heredity of plants advanced the study of genetics.

He is often known as the ‘father of genetics’.

Question 3

What organism did Mendel study to establish the foundations of genetics?

Answer 3

Pea plants.

Question 4

What were some reasons Mendel chose pea plants for his experiments?

Answer 4

• Ease of growth.
• Controllable mating.
• Easily distinguishable features.

Question 5

What are some examples of traits Mendel studied in pea plants?

Answer 5

• Flower color
• Pod shape
• Seed color

Question 6

What did Mendel observe about the inheritance of traits in pea plants?

Answer 6

One trait often dominated or covered up another, leading to the description of dominant and recessive traits.

Question 7

Who studied the concept of natural selection and its impact on genetic variation?

Answer 7

Charles Darwin

Question 8

What is natural selection?

Answer 8

The process by which organisms better adapted to their environment tend to survive and produce more offspring.

Question 9

What are inherited traits?

Answer 9

Traits passed down through generations due to DNA coding.

Question 10

How do genetics and the environment influence traits like hair color?

Answer 10

Genetics provide the base color, while environmental factors like dyeing can change it temporarily.

Question 11

What are chromosomes?

Answer 11

Linear segments of DNA containing many genes.

Question 12

What are the two main types of chromosomes, and what distinguishes them?

Answer 12

• Sex chromosomes: contain genes for primary and secondary sex characteristics.
• Autosomes: contain genes for all other aspects of physiology.

Question 13

What is a gene?

Answer 13

A section of DNA that codes for a particular protein.

Question 14

What are structural genes and regulatory genes?

Answer 14

• Structural genes: code for proteins contributing to cell structure.
• Regulatory genes: control gene expression.

Question 15

What are alleles?

Answer 15

Different versions of a gene that determine specific traits.

E.g. if the gene is eye colour, the alleles may be brown, blue, green, etc.

Question 16

What is the genotype of an organism?

Answer 16

The combination of alleles an organism inherits for a particular gene.

Question 17

What is the phenotype of an organism?

Answer 17

The observable traits of an organism e.g. fur colour.

Question 18

How does a Punnett square help determine offspring genotypes?

Answer 18

It allows you to see the possible combinations of alleles from the parents, predicting the likelihood of certain traits appearing in the offspring.

Question 19

Define a genome.

Answer 19

The complete set of genetic information in an organism.

Question 20

What is the relationship between genotype and phenotype?

Answer 20

Genotype influences phenotype, but environmental factors can also play a role.

Question 21

How does natural selection influence genetic variation in populations?

Answer 21

Organisms with advantageous traits are more likely to survive and pass on their genes, leading to genetic variation over generations.

Question 22

List some example of inherited traits.

Answer 22

• Skin color
• Height
• Coat or feather color
• Ability to resist disease or pests
• Differences in protein function

Question 23

• What is a locus on a chromosome?
• Why is it important in genetics?

Answer 23

• It is a specific location on a chromosome where a particular gene is located.
• It is important because it helps scientists identify and map genes, contributing to our understanding of inheritance and genetic traits.

Question 24

Explain the concept of diploid and homologous chromosomes.

Answer 24

• Humans have two copies of each chromosome, one inherited from each parent, making them diploid.
• The two corresponding copies of a chromosome, one from each parent, are called homologous chromosomes.

Homologous chromosomes carry similar genetic information but may have different alleles for certain genes.

Question 25

What does **DNA** stand for?

Answer 25

Deoxyribonucleic acid

Question 26

How many genes does an individual typically have, and what do they determine?

Answer 26

An individual typically has 20,000 to 25,000 genes, each responsible for a different characteristic, such as eye color or hair color.

Question 27

What is the significance of gametes in reproduction?

Answer 27

* They are special sex cells produced by reproductive glands (testes and ovaries), contain one copy of each gene. * They combine during reproduction to create offspring with a random mixture of genes.

Question 28

How does the expression of dominant and recessive genes work?

Answer 28

* Dominant genes are expressed even with one copy. * Recessive genes require two copies for expression. ## Footnote Dominant alleles are represented by uppercase letters, they mask the effect of recessive alleles, represented by lowercase letters. For example, P (purple) is dominant over p (white).

Question 29

What does the example (in the diagram) of two brown-eyed parents having a blue-eyed child demonstrate?

Answer 29

How recessive traits can be expressed in offspring even when both parents have dominant traits, due to the combination of genes during reproduction.

Question 30

What incorrect belief about heredity did people have before Mendel's discoveries?

Answer 30

People believed that traits were blended together, such as a child having a medium nose if one parent had a large nose and the other a small nose.

Question 31

Define Mendel's first Law. | (called the **Law of Segregation**)

Answer 31

It states that each allele for a trait will segregate, or separate, from its partner (during meiosis) so each gamete will only have one copy of the genetic material.

Question 32

What is the significance of meiosis in Mendel's Law of Segregation?

Answer 32

Meiosis is the process that halves the genetic information in gametes, ensuring that offspring have the correct amount of genetic material when gametes combine.

Question 33

What are the possible genetic combinations for offspring from two Bb (purple flowered) pea plants (as shown in the diagram)?

Answer 33

* 25% chance of BB (purple) * 50% chance of Bb (purple) * 25% chance of bb (white)

Question 34

What did Mendel's experiments reveal about heredity?

Answer 34

It showed that traits are inherited in discrete units (genes) and can reappear in subsequent generations even if they are not visible in the parents.

Question 35

When drawing punnet squares, how do we denote dominant and recessive alleles?

Answer 35

Dominant alleles are represented by uppercase letters, they mask the effect of recessive alleles, represented by lowercase letters. ## Footnote For example, P (purple) is dominant over p (white).

Question 36

Which process results in the formation of 4 haploid, genetically different gametes?

Answer 36

Meiosis

Question 37

Describe **Mendel's Second Law**?

Answer 37

Also known as The law of independent Assortment, it states that the outcome of one gene is not related to the outcome of another gene.

Question 38

Explain how flipping a coin related to Mendel's Second Law?

Answer 38

Just as the result of flipping a quarter does not affect the result of flipping a penny, the outcome of one gene does not affect the outcome of another gene according to Mendel's Second Law.

Question 39

What are **linked genes**?

Answer 39

Linked genes are genes that tend to be inherited together because they are located close to each other on the same chromosome. ## Footnote Example: Red hair and freckles.

Question 40

How did Mendel discover the law of independent assortment?

Answer 40

Through experiments on pea plants, observing the independent assortment of alleles for pea color (yellow or green) and pea shape (round or wrinkled).

Question 41

What did Mendel observe when crossing pea plants for two traits?

Answer 41

That the ratios of 9 yellow round, 3 yellow wrinkled, 3 green round, and 1 green wrinkled, matching the predicted results from a Punnett square.

Question 42

How can Mendel's Second Law help in medical research?

Answer 42

Understanding independent assortment and gene linkage can help scientists discover the genetic basis of diseases and develop treatments by identifying linked genes.

Question 43

Are all genes independently assorted according to Mendel's second law?

Answer 43

No. ## Footnote Some genes are linked together and do not assort independently, such as red hair and freckles.

Question 44

What does it indicate if actual genetic results do not match the expected Punnett square results?

Answer 44

It indicates that the genes might be linked, meaning they do not assort independently and tend to be inherited together.