Lecture 1

Question 1

What did Gregor Mendel’s work lead to?

Answer 1

Discovery of dominant and recessive traits.
Concept of the Gene.
Formulation of laws of inheritance.

Question 2

What is a character in genetics?

Answer 2

Heritable feature of an individual.

Question 3

What is a trait?

Answer 3

Variant form of the character (phenotype).

Question 4

What is the definition for the law of segregation?

How did he come about with this Law?

Answer 4

The two forms of a gene (alleles) present in each parent segregate independently.
Studied results of monohybrid crosses.

Question 5

What is a monohybrid cross?

Answer 5

A cross between 2 true breeding individuals differing in only one character.

Question 6

What were Mendel’s observations when crossing green and yellow pea pods?

Answer 6

All F1 progeny resembled one of their parents.
But both original parental traits appeared in F2 generation.
Ratio in F2 = 3:1.
Same pattern of inheritance seen for all 7 characters studied.

Question 7

Which pods were dominant and recessive in Mendel’s experiments?

Answer 7

Green = dominant.
Yellow = recessive.

Question 8

Had the heritable factor for the recessive trait been lost in the F1 pea pod progeny?

Answer 8

No, just masked by presence of the factor for the dominant trait.

Question 9

Do alleles blend in Mendel’s model?

Answer 9

No, remain discrete.

Question 10

What happens in gamete formation according to Mendel’s model?

Answer 10

Two alleles segregate, ending up in different gametes.

Question 11

What is a method for determining the genotype of an individual with the dominant phenotype of a trait?

Answer 11

Testcross.

Question 12

Define Mendel’s law of independent assortment.

Answer 12

Each pair of alleles assorts independently of each other pair of alleles during gamete formation.

Question 13

What does Mendel’s law of independent assortment relate to?

Answer 13

Situation where the inheritance of two or more different pairs of alleles is being studied.

Question 14

How did Mendel formulate law of independent assortment?

Answer 14

By following inheritance of two characters at the same time.

Question 15

What is a dihybrid cross?

Answer 15

A cross involving parents differing in 2 characters.

Question 16

What results were seen in F2 generation when Mendel crossed yellow-round seeds, and green wrinkled seeds (dihybrid cross)?

Answer 16

Two new phenotypes in addition to 2 parental phenotypes - recombinants.
9:3:3:1.

Question 17

What would happen if independent assortment did not occur in dihybrid crosses?

Answer 17

No recombinant phenotypes in F2, with pairs of alleles inherited together.
Would still be 3:1.

Question 18

How would you calculate probabilities of 3 independent allele pairs occurring on the same object?

Answer 18

Multiply 3 probabilities together.

Question 19

What did Sutton write in his 1902 paper?

Answer 19

The association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division, may constitute the physical basis of the Mendelian law of heredity.

Question 20

How many haploid or diploid cells does mitosis produce?

Answer 20

2- Diploid.

Question 21

How many haploid or diploid cells does meiosis produce?

Answer 21

4 - Haploid.

Question 22

What type of cells does mitosis and meiosis occur in?

Answer 22

Mitosis - somatic cells.

Meiosis - germ line.

Question 23

Does synapsis occur in mitosis or meiosis?

Answer 23

Meiosis.

Question 24

What are the roles of mitosis and meiosis?

Answer 24

Mitosis - drive growth and tissue repair.

Meiosis - produce haploid gametes and introduce genetic invariability.

Question 25

What is a homologous pair?

Answer 25

2 structurally similar chromosomes coding for the same genes with some different alleles from two different parents.

Question 26

What is a chromatid?

Answer 26

One of 2 identical strands of a newly replicated chromosome.

Question 27

What are sister chromatids?

Answer 27

2 identical chromatids held together by a common centromere following replication.

Question 28

What happens in Meiosis 1?

Answer 28

Chromosome replication and recombination.
Homologous chromosomes separate.
Produces two haploid cells.

Question 29

What happens in Meiosis 2?

Answer 29

Chromatids separate.

Produces 4 haploid gametes.

Question 30

What happens in interphase before meiosis?

Answer 30

Chromosomes replicate forming pairs of chromatids.

Chromosomes not yet condensed.

Question 31

Did the behaviour of chromosomes during meiosis influence Mendelian Inheritance?

Answer 31

Yes.

Question 32

What did Sutton observe?

Answer 32

Chromosomes occur in pairs in somatic cells.
Chromosome pairs segregate equally into gametes.
Different chromosome pairs assort independently.

Question 33

What does the chromosome theory of inheritance state?

Answer 33

Mendel’s heritable factors located at specific loci on chromosomes.
The chromosomes undergo segregation and independent assortment.

Question 34

How does chromosome behaviour in meiosis explain Mendel’s Law of Segregation?

Answer 34

Each allele is on a different member of a homologous pair of chromosomes, moving to opposite poles in anaphase I.

Question 35

How does chromosome behaviour in meiosis explain Mendel’s Law of Independent Assortment?

Answer 35

The random way in which the homologous pairs of chromosomes lineup on the metaphase plate during meiosis I.