Principles of inheritance and variation

Question 1

Gene

Answer 1

it is the basic unit of inheritance. contains the information on a particular trait

Question 2

allelles

Answer 2

allelles are genes with 2 contrasting characteristics

Question 3

homozygous

Answer 3

both allelles are identical

Question 4

heterozygous

Answer 4

both allelles are non identical

Question 5

dominant allelle

Answer 5

it is the allelle that expresses itself in homozygous as well as heterozygous.

Question 6

recessive allelle

Answer 6

The factor which fails to express itself in the presence of its contrasting allele. A recessive factor expresses itself only in homozygous condition

Question 7

Hybrid:-
Monohybrid cross:-
Dihybrid cross:-

Answer 7

The offspring produced by a cross between two individuals differing in one or more characters. Eg. Tt
Cross between two parents differing in one pair of contrasting characters. Eg. Tall * Dwarf
Cross between two parents differing in two pairs of contrasting characters. Eg. Tall Red * Dwarf White

Question 8

true breeding line

Answer 8

having undergone continuous self pollination
ii. shows stable trait inheritance and expression for several
generations

Question 9

LAW OF DOMINANCE

Answer 9

Characters are controlled by discrete units called factors.
Factors occur in pairs.
In a dissimilar pair of factors,one member of the pair dominates (dominant) the other (recessive)

Question 10

LAW OF SEGREGATION

Answer 10

Two alleles of a pair representing a character, will segregate or separate from each other during gamete formation , so that a gamete receives only one of the two factors (never both).
The paired condition is restored during gamete fusion.

Question 11

Mendel’s Law of Independent Assortment

Answer 11

When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of other pair of characters”.

Question 12

INCOMPLETE DOMINANCE

Answer 12

Type of inheritance in which one allele is not completely dominant over the other.

Question 13

MULTIPLE ALLELISM

Answer 13

Presence of more than two alleles for a gene

Question 14

PLEIOTROPY

Answer 14

Phenomenon in which single gene exhibits multiple phenotypic expression.
Such a gene is called a pleiotropic gene.

Question 15

Morgan worked with the tiny fruit flies Drosophila melanogaster.

Answer 15

. They could be grown in simple synthetic medium in the lab.
2. They complete their life cycle in about two weeks.
3. Single mating produces large number of progeny flies.
4. There is clear differentiation between the sexes.
5. It has many types of hereditary variations that
can be seen with low power microscope.

Question 16

linkage

recombination

Answer 16

physical association of two genes

generation of non parental gene recombination’s

Question 17

genetic maps

Answer 17

alfred sturtevant

frequency of recombination between gene pairs on the same chromosome as a measure of distance between genes and mapped.

Question 18

polygenic traits

example

Answer 18

some traits are controlled by three or more genes and are thus called polygenic traits

Question 19

pleiotropy

example

Answer 19

it is when a single gene exhibits multiple phenotypic expression

Question 20

mutation

point mutation

Answer 20

alteration of DNA and consequently results on changes in the genotype and phenotype of an organism
a change in a a single base pair of DNA

Question 21

pedigree analysis

Answer 21

analysis of traits in several generations of a family

Question 22

mendelian disorders

chromosomal disorders

Answer 22

alteration or mutation in a single gene

caused due to absence of excess or abnormal arrangement of one or more chromosomes

Question 23

color blindness
haemophilia
sickle cell anaemia
phenylketonuria
thalassemia

Answer 23

defect in recognizing red-green. x linked
x linked. clotting of blood is affected
autosome related shape of rbc to sickle shape
autosomal. mental retardation loss of hair and skin pigmentation
autosome. hemoglobin production is affected

Question 24

aneuploidy

polyploidy

Answer 24

failure of segregation of chromatids during cell division results in the gain or loss of chromosomes.
failure of cytokinesis after telophase stage of cell division resulting in gain of extra set of chromosomes

Question 25

down syndrome
Klinefelter’s syndrome
turners syndrome

Answer 25

presence of an additional copy of the chromosome no 21 trisomy 21
presence of an additional copy of x chromosome
absence of one of the x chromosomes