Flashcards For NEET Biology - Principles of Inheritance and Variation

Flashcards for NEET Biology are designed to boost your NEET preparation. Find below flashcards for Principles of Inheritance and Variation. These flashcards on Principles of Inheritance and Variation are prepared as per the NEET syllabus. This is helpful for aspirants of NEET and other exams during last-minute revision. Flashcards For NEET Biology – Principles of Inheritance and Variation, covers all the important points that are frequently asked in the exam. Check BYJU’S for the full set of Flashcards and Study material for NEET Biology. Solve NEET Biology MCQs to check your understanding and outperform in the exam.

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Name of the NEET sub-section

Topic

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Biology

Principles of Inheritance and Variation

NEET exams

 

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Principles of Inheritance and Variation

Seven contrasting traits in Mendel’s experiments

-Seed shape, round and wrinkled

-Seed colour, yellow and green

-Flower colour, violet and white

-Pod shape, full and constricted

-Pod colour, green and yellow

-Flower position, axial and terminal

-Stem height, tall and dwarf

Genes

Unit of inheritance

Responsible for expression of any trait

Alleles

Variants of a gene present at the same locus on homologous chromosomes

Genotype

Genetic constituent of organisms

Homozygote- identical pair of alleles

Heterozygote- dissimilar pair of alleles

Phenotype

External and morphological appearance of a trait

Dominant trait- which is expressed in both homozygotes and heterozygotes

Recessive trait- which is only expressed in homozygotes

Monohybrid cross

Inheritance study of only one character

Phenotypic ratio- 3:1

Genotypic ratio- 1:2:1

Dihybrid cross

Inheritance study of two characters

Phenotypic ratio- 9:3:3:1

Genotypic ratio- 1:2:1:2:4:2:1:2:1

Back cross

Cross of filial1 or F1 progeny with any parent

Test cross

Cross of F1 progeny with the recessive homozygous parent

Used to determine genotype of F1 individual showing dominant phenotype

Reciprocal cross

The male and female parents are changed

Incomplete dominance

Dominant trait does not completely mask the recessive trait

F1 phenotype does not resemble any parent, instead, shows a blending of alleles

E.g. Antirrhinum (snapdragon), Mirabilis jalapa

Multiple alleles

More than one alleles for a gene or character

E.g. ABO blood group, gene I exist in three forms

Chromosomal theory of inheritance

Sutton and Boveri

Linkage

T H Morgan coined the term

Association of genes in close proximity on the same chromosomes

Closely linked genes show low recombination and mostly inherited together

Polygenic inheritance

Inheritance of a trait controlled by many genes

E.g. skin colour, height in humans

Pleiotropic genes

A gene, which controls more than one characters

E.g. A defective gene causing phenylketonuria

Epistasis

When a gene suppresses the effect of non-allelic gene

E.g. hair colour and baldness, wheat kernel colour, coat colour in horses

Male heterogamety

Different types of gametes produced by males

E.g. XO in insects, XY in humans and Drosophila

Female heterogamety

Different types of gametes produced by females

E.g. ZW in birds

Parthenogenesis

Development of an individual from an unfertilised egg

E.g. male drones of honey bees contain haploid chromosomes

Mutation

Change in the DNA sequence due to deletion, insertion or substitution

Point mutation- change in single base pair in DNA, e.g. sickle cell anaemia

Frame-shift mutation- due to deletion or insertion of base pairs

Colour blindness

X-linked recessive

Haemophilia

X-linked recessive

Sickle-cell anaemia

Autosomal recessive

Glu (GAG) changes to Val (GUG) at the 6th position codon of β-globin chain of haemoglobin

Phenylketonuria

Autosomal recessive

Caused by mutation in the gene coding for enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine

Thalassemia

Autosomal recessive

Defective genes for 𝛼 or β globin chains of haemoglobin

𝛼-Thalassemia- HBA1 and HBA2 gene on chromosome 16

β-Thalassemia- gene HBB on chromosome 11

Aneuploidy

Loss or gain of an extra chromosome

Caused when chromatids fail to segregate during cell division

E.g. Down’s syndrome, Turner’s syndrome, etc.

Polyploidy

Gain of a full set of chromosomes

Caused when cytokinesis does not follow karyokinesis

Common in plants

Down’s syndrome

Trisomy of 21st chromosome

Klinefelter’s syndrome

Additional X chromosome

XXY

Turner’s syndrome

Monosomy, one of the sex chromosomes is missing

XO

True breeding plant

Stable trait inheritance for several generations on self-fertilisation

Homozygous for traits

Produces similar offsprings on self-fertilisation

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