History of Genetics

Question 1

What is genetics?

Answer 1

The study of heredity—how traits are passed from parents to offspring.

Question 2

How was early genetics shaped?

Answer 2

By observations of trait inheritance patterns, long before DNA was discovered.

Question 3

What does the Law of Segregation state?

Answer 3

Each organism has two alleles for each trait—one from each parent, which segregate so only one is passed to each gamete randomly.

Question 4

What is the Law of Independent Assortment?

Answer 4

Genes for different traits are inherited independently, provided they are on different chromosomes.

Question 5

What does the Law of Dominance explain?

Answer 5

Some alleles are dominant (expressed), while others are recessive (masked unless both alleles are recessive).

Question 6

What is the purpose of mitosis?

Answer 6

To enable growth, repair, and replacement by producing identical diploid cells.

Question 7

What occurs during Interphase in mitosis?

Answer 7

Cell grows (G1), replicates DNA (S), prepares for division (G2).

Question 8

What happens during Prophase in mitosis?

Answer 8

DNA condenses into chromosomes; spindle forms.

Question 9

What occurs in Metaphase of mitosis?

Answer 9

Chromosomes align on the metaphase plate.

Question 10

What happens during Anaphase in mitosis?

Answer 10

Sister chromatids are pulled apart to opposite poles.

Question 11

What is the outcome of Telophase in mitosis?

Answer 11

Nuclear envelope reforms; DNA decondenses.

Question 12

What is cytokinesis?

Answer 12

The division of the cytoplasm into two diploid daughter cells.

Question 13

What is the main difference between mitosis and meiosis?

Answer 13

Meiosis occurs only in germ cells (sperm/egg) and produces four genetically unique haploid cells.

Question 14

What role do Sutton and Boveri play in genetics?

Answer 14

Sutton: Chromosome behavior during meiosis matches Mendel’s principles; Boveri: Egg and sperm each contribute half of the chromosome set to the zygote.

Question 15

What occurs during Prophase I of meiosis?

Answer 15

Homologous chromosomes pair; crossing over occurs.

Question 16

What happens in Metaphase I of meiosis?

Answer 16

Pairs align at the equator.

Question 17

What is the outcome of Anaphase I in meiosis?

Answer 17

Homologous chromosomes separate (not sister chromatids).

Question 18

What occurs during Telophase I of meiosis?

Answer 18

Cell prepares for the second division.

Question 19

What is the purpose of Meiosis II?

Answer 19

To separate sister chromatids.

Question 20

What happens during Prophase II of meiosis?

Answer 20

Nuclear envelope dissolves again.

Question 21

What occurs in Metaphase II of meiosis?

Answer 21

Chromosomes align.

Question 22

What happens during Anaphase II of meiosis?

Answer 22

Sister chromatids separate.

Question 23

What is the outcome of Telophase II in meiosis?

Answer 23

Four haploid gametes are formed.

Question 24

What is a dominant allele?

Answer 24

Masks the effect of a recessive allele

Dominant alleles express their traits even when only one copy is present.

Question 25

What is a recessive allele?

Answer 25

Only shows its effect when two copies are present ## Footnote Recessive alleles require both copies to express their traits.

Question 26

What was the classic example used by Mendel to demonstrate dominance?

Answer 26

Pea plants: Round (dominant) × Wrinkled (recessive) ## Footnote Mendel's experiments showcased the inheritance patterns of traits in pea plants.

Question 27

What is the phenotypic ratio in the second generation (F2) of Mendel's pea plant experiment?

Answer 27

3:1 (Round : Wrinkled) ## Footnote This ratio indicates the observable traits in the offspring.

Question 28

What is the genotypic ratio in the second generation (F2) of Mendel's pea plant experiment?

Answer 28

1:2:1 (RR : Rr : rr) ## Footnote This ratio reflects the genetic makeup of the offspring.

Question 29

What is alkaptonuria?

Answer 29

A recessive condition caused by a homozygous recessive mutation ## Footnote It leads to a complete block in a biochemical pathway.

Question 30

What are the characteristics of alkaptonuria?

Answer 30

Metabolite accumulation and deposition in joints, eyes, etc. ## Footnote This condition results from the inability to properly process certain metabolites.

Question 31

What is required to cause the disease of alkaptonuria?

Answer 31

Need two loss-of-function alleles ## Footnote Presence of only one functional allele can maintain a normal phenotype.

Question 32

What is the typical functional interpretation of dominant alleles?

Answer 32

Typically functional or gain-of-function ## Footnote Dominant alleles often enhance or create a trait.

Question 33

What are recessive alleles usually characterized as?

Answer 33

Usually loss-of-function – a broken or non-working copy ## Footnote Recessive alleles fail to produce a functional product.

Question 34

What does dosage sensitivity refer to in genetics?

Answer 34

If a trait is not dosage-sensitive, one working copy is enough → dominant ## Footnote Dosage sensitivity affects how alleles express traits.

Question 35

What is the consequence of losing function when both copies are mutated?

Answer 35

Recessive phenotype ## Footnote This occurs when the trait requires both alleles to function properly.

Question 36

What is the cancer risk associated with having one mutated BRCA1 copy?

Answer 36

50–65% risk of breast cancer by age 70 ## Footnote This illustrates the significance of genetic mutations in cancer predisposition.

Question 37

What typically happens with two mutated BRCA1 copies?

Answer 37

Embryonic lethal outcome ## Footnote Two copies of the mutated allele often lead to non-viability.

Question 38

What is a key point regarding the effects of the same allele?

Answer 38

Same allele can have different effects depending on the phenotype measured ## Footnote Dominant effects may include cancer risk, while recessive effects can lead to non-viability.