Definition and Significance of Test Cross

Q.

Define and design a test-cross.

Q. Give a genetic explanation for the following cross. When a tall pea plant with round seeds was crossed with a dwarf pea plant with wrinkled seeds then all the individual of F1-populations were tall with round seeds. However selfing among $F_1$-population led to a 9 : 3 : 3 :1 phenotypic ratio. [5]

Q.

A child has blood group O. If the father has blood group A and mother has blood group B, what would be the possible genotypes of other offspring?

Q. Ratio of progeny, when a red coloured heterozygote is crossed with a white coloured plant in which red colour is dominant to white colour

1. 3:1
2. 1:1
3. 1:2:1
4. 9:3:3:1

Q. Progeny with blood group O cannot be obtained when

1. a male with A blood group mates with a female having A blood group
2. a male with B blood group mates with a female having B blood group
3. a male with O blood group mates with a female having AB blood group
4. a male with A blood group mates with a female having B blood group

Q. $F_2$ generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1. It represents a case of:

1. Dihybrid cross
2. Monohybrid cross with complete dominance
3. Monohybrid cross with incomplete dominance
4. Co-dominance

Q. Test cross is performed to know the genotype of a dominant phenotype. It is a cross between

1. none of the above
2. $F_1$ hybrid with dominant parent
3. two $F_1$ hybrids
4. $F_1$ hybrid with recessive parent

Q. A cross between two homozygous individuals differing in two characters is called

1. reciprocal cross
2. monohybrid cross
3. dihybrid cross
4. test cross

Q. A father with type B blood and mother with type A blood have a child. Their child has discovered that her blood group is type O, during biology experiment at her school. Does she have any concerns about her parentage?

1. Yes, because she should have type AB blood if they are her true biological parents
2. No, because type O blood is possible if her parents both had genotye AB.
3. No, because both of her parents could be heterozygous
4. Yes, because both of her parents might be heterozygous
5. No, because blood types A and B are codominant

Q. Very short answer type.
Distinguish between back cross and test cross.

Q. In pigs, white coat (W) is dominant to black (w). Two white pigs are bred to produce nine white and two black pigs. What are the genotypes of the parents?

1. $WW\times Ww$
2. $WW\times WW$
3. $Ww\times Ww$
4. $ww\times ww$

Q. Differentiate between.
Back cross and test cross

Q. A child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.

Q. A common test to find the genotype of a hybrid is by :

1. Crossing of one $F_2$ progeny with female parent
2. Studying the sexual behaviour of $F_1$ progenies
3. Crossing of one $F_2$ progeny with male parent
4. Crossing of one $F_1$ progeny with male parent

Q. What is the ratio of progeny, when a red-flowered heterozygous plant is crossed with a white-flowered plant, in which red flower is dominant to white flower?

1. 3 : 1
2. 1 : 1
3. 1 : 2 : 1
4. 9 : 3 : 3 : 1

Q.

A cross between a true tall and pure dwarf pea plant results in production of all tall plant because tallness is the dominant trait.

1. True
2. False

Q. Test cross involves :

1. Crossing the $F_1$ hybrid with a double recessive genotype
2. Crossing between two genotypes with dominant trait
3. Crossing between two $F_1$ hybrids
4. Crossing between two genotypes with recessive trait

Q.

Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called:

1. Reciprocal cross

2. Test cross

3. Dihybrid cross

4. Back cross

Q. Choose the correct answer from the alternatives given.

1. 6
2. 2
3. 3
4. 4

Q. If one parent has blood group A and the other parent has blood group B, the offsprings have which blood group?

1. AB only
2. O only
3. B only
4. A, B, AB and O

Q. What is the ratio of progeny, when a red-flowered heterozygous plant is crossed with a white-flowered plant, in which red flower is dominant to white flower?

1. 3 : 1
2. 1 : 1
3. 1 : 2 : 1
4. 9 : 3 : 3 : 1

Q. ABO blood groups in humans is controlled by the gene I. It has three alleles: I${}^A$, I${}^B$ and i. Since, there are three different alleles, six different genotypes are possible. How many phenotypes can occur?

1. Two
2. Four
3. Three
4. One

Q. In a family, father has a blood group A and mother has a blood group B. Their children show 50% probability for a blood group AB indicating that

1. Mother is homozygous
2. Father is heterozygous
3. Mother is heterozygous
4. Either of parent is heterozygous

Q.

Paragraph for below question

नीचे दिये गये प्रश्न के लिए अनुच्छेद

Three genes A, B and C control skin colour in human with the dominant forms A, B and C responsible for dark skin colour and the recessive forms a, b and c for light skin colour. The genotype with all the dominant alleles will have the darkest skin colour and that with all the recessive alleles will have the lightest skin colour.

On the basis of above paragraph, answer the given question.

तीन जीन A, B तथा C मानव में त्वचा रंग को नियंत्रित करते हैं जिसमें प्रभावी रूप A, B तथा C गहरे त्वचा रंग के लिए उत्तरदायी होते हैं तथा अप्रभावी रूप a, b तथा c गोरे त्वचा रंग के लिए उत्तरदायी होते हैं। सभी प्रभावी अलीलों वाले जीनप्ररूप (जीनोटाइप) में सबसे गहरा त्वचा रंग होगा तथा सभी अप्रभावी अलीलों वाले जीनप्ररूप (जीनोटाइप) में सबसे गोरा त्वचा रंग होगा।

उपरोक्त अनुच्छेद के आधार पर दिए गए प्रश्न का उत्तर दीजिए।

Q. How many phenotypes are possible in F₂ generation w.r.t. inheritance of skin colour in human when it is controlled by 3 pairs of polygenes?

प्रश्न - मानव में त्वचा रंग की वंशागति के संदर्भ में F₂ पीढ़ी में कितने लक्षणप्ररूप (फीनोटाइप) संभावित होते हैं जब यह बहुजीनों के तीन युग्मों द्वारा नियंत्रित होती है?

1. 64
2. 27
3. 7
4. 9

Q. How many types of gametes are found in F₁ progeny of cross AA BB CC and aa bb cc

1. 3
2. 8
3. 27
4. 64

Q. What would be blood groups of the progeny of father A and mother homozygous B

1. A and B
2. AB and A
3. O
4. AB and B

Q. A child's blood group is 'O'. Which of the following blood group his parents cannot have?

1. B and O
2. AB
3. A and B
4. A and O

Q. If the blood group of father is 'A' and that of mother is 'B', the blood group of their child could be

1. AB only
2. A or B or AB or O
3. A or B only
4. A or B or AB

Q. In order to find out the different types of gametes produced by pea plant having the genotype AaBb, it should be crossed to a plant with the genotype

1. AaBb
2. aabb
3. AABB
4. aaBB

Q. Choose the correct answer from the alternatives given.
Consider a cross in which a trait is inherited by complete dominance. What percentage of the F2 from the mating of homozygous dominant and homozygous recessive individuals will possess the heterozygous genotype?

1. 75 per cent
2. 50 percent
3. 25 percent
4. 0 percent