Biology 1 Marks Question

Sutton and Boveri proposed the chromosomal theory of inheritance in 1902.

Test cross.

Anaphase-1 of Meiosis -1/Anaphase -1.

Test cross.

Male Honey bee develops from unfertilized female gamete/unfertilised egg/Parthenogenesis of female gamete (16 chromosomes), female develops by fertilisation/fertilised egg (32 chromosomes).

Round/Wrinkled, Yellow/Green.

Axial, violet flower.

Autosomal dominant–Myotonic dystrophy.
Autosomal recessive–Phenylketonuria/sickle cell anaemia/cystic fibrosis/Thalesemia.

Insertion, deletion of three bases/one codon or multiple of three bases/multiple codon (hence one or more amino acid) (reading frame remains unaltered from that point onwards)

All the physical and chemical factors that induce mutation, UV radiation/X rays.

Male-ZZ, Female-ZW.

Arising due to change in a single base pair of DNA, sickle cell anemia.

Inheritable mutations (in a population), at high frequency.

Segregate/separate.

Gene - contains information that is required to express a particular trait//unit of inheritance//segment of DNA called cistron//
Sequence of DNA coding for tRNA/rRNA/polypeptide/enzyme.
Allele - Genes which code for a pair of contrasting traits/(slightly) different forms of the same gene/individual gene in a particular gene pair (for same character).

Many generations can be obtained (in a short time).
variations can be exhibited/selected faster.

Inflated, green pods.

Failure of segregation of chromatids/non-disjunction/aneuploidy.

Monohybrid cross is a cross made between two individuals of a species, considering the inheritance of the contrasting pair of a single character/ trait.

Mendel could not have framed the law of independent assortment, if the genes for all the characters Mendel chose, were present on the same chromosome and showed the phenomenon of linkage.

1. Humans: colour-blindness, haemophilia.
2. Drosophila: Eye colour, body colour.

It is a sex-linked (X-linked) disorder.

Drosophila melanogaster.

The two characters of pea plant used by Mendel in his hybridisation experiment are:

1. Flower colour: violet and white.
2. Pod colour: Green and yellow.

The strength of linkage increases as the distance between two linked genes decreases. The linkage becomes weaker with the increase in the distance between genes.

Female fowl (with ZW sex chromosomes).

Possible genotypes: Tt and tt.

Cancerous cells.

Skin colour in humans is controlled by three different genes and the phenotype is the cumulative effect of all the dominant alleles; hence, its inheritance is considered as polygenic.

Axial, Violet flower.

The genes which tend to transmit together as a unit, as they are located very close on the same chromosome are called linked genes.

I and I are codominant alleles.

Punnett square can be effectively used to understand the independent segregation of the two pairs of genes during meiosis.

The defective allele (for haemophilia) is present on the X-chromosome, which the son does not get from his father.

Colour blindness.

Johannsen in 1909.

When the genes situated on the same chromosome.

The observable or external morphological characteristics (features) of an organism constitute its phenotype.

1. The individual will be a male.
2. He suffers from Klinefelter's syndrome.

When the genes are linked.

2. In grasshopper males, there exists XO type of sex determination.

Wrinkled seed shape is a recessive trait. It expresses only under homozygous condition of alleles.

Insertion and deletion of three bases or multiples of three bases cause frame–shift mutation because the reading frame remains unaltered from that point onwards.

The presence of a chromosome as a single copy in a diploid cell is termed as monosomic condition.

1. Down’s syndrome.
2. Klinefelter’s syndrome.

Snapdragon (Antirrhinum sp.) shows same genotypic and phenotypic ratios for inheritance of flower colour.

Monosomy of sex chromosome in females (XO condition).

1. Incomplete dominance.
2. Dominance.