Principles of Inheritance

Question 1

3 steps in conducting an artificial cross:

Answer 1

• Selection
• Emasculation
• Pollitation
• Germination and collection

Question 2

How many contrasting traits did Mendel study?

Answer 2

7

Question 3

Monohybrid phenotypic ratio

Answer 3

3:1
3 tall: 1 dwarf

Question 4

Monohybrid genotypic ratio

Answer 4

1:2:1
1 TT: 2Tt: 1tt

Question 5

Monohybrid test cross ratio:

Answer 5

1:1

If 1:1, then F1 = Heterozygrous
If 100%, then F1 = homozygous

Question 6

Laws of inheritance:

Answer 6

• Law of dominance
• Law of segregation
• Law of independent assortment

Question 7

Law of dominance:

Answer 7

Characters in an individual are controlled by discerete units called factors.
Factors occur in pairs
In a dissimilar factor pair, one memeber is recessive, and the other dominant.

Question 8

Law of Segregation:

Answer 8

During gamete formation, the alleles of the parent separate in such a way that each gamete only receives one allele from each parent.
A homozygous parent produces identical alles
A heterozygous parent produces dissimilar alles

Question 9

Dihybrid phenotypic ratio:

Answer 9

9:3:3:1
9 Round Yellow: 3 Round Green: 3 Wrinkled Yellow: 1 Wrinkled green

Question 10

Dihybrid genotypic ratio

Answer 10

1:2:2:4:1:2:1:2:1

Question 11

Law of independent assortment:

Answer 11

When more than one pair of characters is involved in a cross, the alleles of the factor pairs segregate independently from each toher

Question 12

When the F1 shows an intermediate character, between that of the two parents:

Answer 12

Incomplete dominance
(ex// antrirrhimum and mirabilis jalapa and seed size in pea plants )

Question 13

Incomplete dominance monohybrid phenotypic ratio:

Answer 13

1:2:1
1 Red: 2 Pink: 1 White

Question 14

When the F1 generation resembles both parents:

Answer 14

Co-dominance
(ex/ABO blood grouping)

Question 15

When a gene has more than 2 alternate forms (more than 2 alleles):

Answer 15

Multiple allelism

Question 16

When more than one gene controls a particular trait:

Answer 16

Polygenic inheritance
(ex// skin colour or height in humans)

Question 17

Pleiotropy:

Answer 17

One gene is responsible for more than 1 character trait.
(ex// phenylkeotnuria or sickle cell anaemia or starch synthesis in pea plants)

Question 18

Who rediscovered Mendel’s results:

Answer 18

De Veries, Correns and Von Tschermak

Question 19

Who proposed the Chromosal Theory of Inheritance?

Answer 19

Walter Sutton and Theodore Boveri

Question 20

Chrosomal Theory:

Answer 20

• Chromosomes are the vehicles of heridity
• Similar chromosomes are found in pairs called homologous pairs
• The homologous pair seperates during gamete formation.
• The independent pairs are segregated independently

(Alles are located in the loci of the chromosomes)

Question 21

Scientific name (fruit flies)

Answer 21

Drosophila melanogaster

Question 22

Recombination occurs due to:

Answer 22

• crossing over
• independent assortment

Question 23

Cross 1 performed by Morgan:

Answer 23

Yellow bodied, white eyes, females ( y,y,w,w )
x
Brown bodied, red eyes, males (dominant and wild) ( y+ , y +, w + , w+)

1.3 % recombination and 98.7% linkage

Question 24

Cross 2 performed by Morgan:

Answer 24

White eyed, miniature winged ( wwmm )
Red eyed, large winged ( w+ w+ m+ m+ )

37.2% recombination and 62.8% linkage

Question 25

Alfred Sturtervant:

Answer 25

He used the frequency of recombination b/w genes on the same chromosome to measure the distance between them and map their position.

Question 26

Mechanisms of sex determination:

Answer 26

XX-XO
XX- XY
ZZ-ZW

Question 27

Diploid content in honeybees:

Answer 27

32 chromosomes

Females produce sperm through meiosis

Question 28

Haploid content in honeybees:

Answer 28

16 chromosomes

Males produce sperm through mitosis

Question 29

Sex determination in bees:

Answer 29

Halpodiploid sex determination

Question 30

What causes variation in DNA?

Answer 30

• Recombination
• Mutation

Question 31

Types of mutation:

Answer 31

• Point mutation (change in a single base pair)
• Frame-shirt mutation (addition/deletion of a base pair)

Question 32

Mutagents can be:

Answer 32

• Physical mutagents
• Chemical mutagents

Question 33

Pedigree Analysis:

Answer 33

The analysis and study of the inheritance of a certain trait in several generations of a family, used to trace the inheritance of a certain condition.

Question 34

Genetic disorders can be:

Answer 34

• Sex linked
• Autosomal

Question 35

Genetic disorders can also be classified into:

Answer 35

• Mendelian
• Chromosomal

Question 36

Mendelian Disorders:

Answer 36

• Haemophilia ( sex linked, recessive)
• Colour blindless (sex linked, recessive)
• Sickle Cell anaemia (autosomal, recessive)
• Phenylketonuria (autosomal, recessive)
• Thalassemia (autosomal, recessive)
• Cystic Fibrosis
• Myotonic dystrophy (dominant)

Question 37

Sickle cell anaemia:

Answer 37

• single base substituion (GAG to GUG), and Glutamine int eh 6th position of the Beta globin chain is replaced by Valine.

Question 38

Phenylketonuria:

Answer 38

The gene producing enzyme phenyl alanine hydroxylase (converts amino acid phenylalanine to tryosine) is affected.

Question 39

Thalassemia:

Answer 39

Mutation that causes the reduced synthesis of one of the alpha or beta globin chains of haemoglobin, forming abnormal haemoglobin and causing anaemia.

Alpha thalassemia = chromosome 16 (2 genes: HbA1 and HbA2)
Beta thalassemia = chromosome 11 (1 gene HBB)

Question 40

Chromosomal disorders:

Answer 40

• Aneuploidy
• Polyploidy

Question 41

Aneuploidy:

Answer 41

• Down’s syndrome
• Klinefelter’s syndrome
• Turner’s syndrome

Question 42

Down’s syndrome

Answer 42

Triosomy of chromosome 21

45A + XX or 45A + XY (total of 47 chromosomes)

Features: small, round head, furrowed tongue, short stature, partially open mouth, broad, flat face, broad palm with Simian crease, congenital heart disease, psychomotor, physical and mental disabilities.

Question 43

Klinefelter’s syndrome:

Answer 43

Additional copy of the X chromosome in males

44 + XXY (Karyotype of 47)

Overall masculine development, but feminine development is also seen. (ex// development of breasts (gynaecomastia))
Sterile individuals, may/may not have mental disabilities.

Question 44

Turner’s syndrome:

Answer 44

Absence of one X chromosome in females

44 + XO

Rudimentary ovaries, lack of secondary sexual characteristics, sterile, dwarf, may/may not be mentally disable.