Chapter 5: Principles of Inheritance & Variation (Part 1)

Inheritance: Process by which character are passed from parents to progeny. Basis of heredity
            Term Genetics: Bateson

Heredity: Transmission of Characters

Variation: Degree by which progeny differs from parents. Cause: Sexual rep

Exploited by humans for developing high yielding var of plants & animals. E.g. Sahiwal cows from wild cows by artificial selection & domestication.

Mendel: On basis of hybridization exp on garden peas (Pisum sativum -14 chr) for 7 yrs Work rediscovered 34 yrs later by DeVries, Correns & Tschermak Unique features of Mendel’s research: ·       Applied math & statistics to study biology ·       Large sample size ·       Continuous experiments on successive generations

•     Studied visible traits with contrasting characters

Father of Genetics: Mendel Checkpoint: At this point it is very important to review few terms: ·        Gene vs Allele ·        Homozygous vs Heterozygous ·        Dominant vs Recessive ·        Genotype Vs Phenotype Make sure that you know them all clearly & confidently before proceeding ahead.

Mendel's Procedure: Artificial/cross pollination using true breeding plants

Selected 14 true breeding plants similar in all respects except 1 contrasting character
Inheritance of one Gene: Monohybrid Cross; Only one allelic pair considered

Dihybrid Cross: Two allelic pairs considered.

Laws of Inheritance: 3  Law of Dominance: In a hybrid where both contrasting alleles present, only 1 factor/allele expresses itself, this is known as dominant allele. The other – recessive               In F2: dominant : recessive:: 3:1  Principle of segregation: When a pair of contrasting characters present in an organisms, the characters do not mix together, simply stay together. They are separated at the time of gamete formation, so that each gamete will have allele for only 1 contrasting trait.              Also k/a Law of Purity of Gametes

• Principle of Independent Assortment: Genes of different characters present together in a plant are not inherited together. They are inherited independent of each other.

A father produces two types of gametes, while a mother produces only 1 type. Which of Mendel’s law is justified by this? State if there are any situations which under normal circumstances show exception to this law.

Cause of Dominance: When one of the alleles in a heterozygous individual is non-functional, i.e. either is not transcribed, or does not produces a functional protein. That allele is recessive. The other functional allele is dominant.

Dominance is relative

Reciprocal Cross: two crosses with same characters taken in to consideration but with reversing the sexes.

Back Cross: Cross of F1 progeny with either of the parent

Test Cross: Crossing of F1 progeny with homozygous recessive parent. Used to determine whether an individual with dominant trait is homozygous or heterozygous. During Test Cross:

All Tall: Homozygous                                                   Tall: Dwarf=1:1 Heterozygous

When Aa is crossed with aa, what is the genotype and ratio of various genotypes in progeny? Can you give a name for this type of cross?

Reasons for Mendel’s Success:        Self-Fertilizing, easy to grow plant        Diploid plant        7 visible features Focused on few contrasting characters, 1 or 2 at time Kept accurate quantitative records

Post Mendel studies revealed interactions between genes.

Post Mendelism: Mendel stated ‘factors’ (genes) to be discrete units inherited independently of each other.

Gene Interactions of 2 types: Intragenic (Interallelic): between two alleles, present on same gene locus on two homologous chromosomes. E.g. Incomplete Dominance, Codominance, Multiple Alleles.

Intergenic (Non-Allelic): two or more independent genes present on same or different chromosomes. E.g. epistasis, duplicate genes, complementary genes.

Incomplete Dominance: Dominant gene does not completely express itself in heterozygotes. E.g. Mirabilis jalapa, P: Dom-Red, Rec- White F1: Pink

F1 genotypic ratio & Phenotypic ratio: 1:2:1

Codominance: Alleles expressed equally in F1.  E.g. Coat colour in Cattle. P: Black Coat & White Coat F1: Neither black/white, but fur with both white & black in patches (roan coat colour)

Genotypic & Phenotypic 1:2:1

Multiple Alleles: More than 2 alleles for a gene. Located at same locus, in different organisms in a population. At a time one organism has only 2 forms of these alleles, & a gamete has only one form (??)

e.g. Blood Groups in humans

Blood Groups: ABO type – discovery: Dr. Karl Landsteiner) Gene I; 3 alleles IA, IB, IO Any 2 forms present in a person; so the genotype combinations can be:__________, _________, _________, _________, _________, ___________ (Total 6) IA& IB Are codominant, while  IO is recessive to  IA& IB On this basis work out the phenotypes from the genotypes you’ve listed above

Thus ABO blood gp is an example of Codominance & Multiple Allelism Cause of Blood Gps: The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene I.

Pleiotropism: when one gene controls more than 1 phenotype.  E.g ·       Sickle Cells anaemia: Gene controls shape of RBC, & O2 carrying efficiency ·       B gene in Pea seeds: 2 forms B, b Phenotype 1 ü  BB: large starch grains, more efficient starch synthesis ü  Bb: intermediate size starch grains ü  bb: small starch grains, less efficient starch synthesis             Phenotype 2 ü  BB: round seeds ü  Bb: round seeds ü  Bb: wrinkled seeds

Can you tell the difference in expression pattern of the two phenotypes ??

Polygenic Inheritance: Poly ______; Genic: _______ Character expression controlled by many genes 3 or more genes have a cumulative effect on a particular character. Each dominant allele expresses a part of the trait. Full trait expression when all dominant alleles present. e.g. Kernel colour in wheat (2 pairs of genes) Height in humans (10 or more pairs of genes)

(interestingly shortness is dominant; so more the number of dominant alleles; shorter the person will be). Further height is also influenced by many environmental factors.

LIFE PROCESSES: INTRODUCTION

MOVEMENT & LIFE

–Visible movements are indicative of life

–Visible Movements can be:

üGrowth related

üNon growth related

–Some movements invisible to naked eye:

vVery small scale / molecular level movements

Molecular movements are defining criteria of life

            CYTOPLASMIC STREAMING: MOVEMENTS AT CELLULAR LEVEL

Required for repair & maintenance of organized structure

*Virus: show molecular structure only when in host cell

LIFE PROCESSES: Maintenance Processes in living organisms

–Processes essential for life

–Performed even when body seems to be doing nothing

–Require energy

They include:

qNutrition: to obtain food from outside. Food is source of energy. Common element in food C

qRespiration: For breakdown & burning of food, to obtain energy in a common form ATP. Requires O2. Involves oxidizing reducing reactions.

qTransportation: to carry food &  O2 to all parts of body

qExcretion: removal of by products / waste

Unicellular vs Multicellular:

vIn unicellular organisms Diffusion is sufficient to provide for exchange.

vIn multicellular diffusion not so because:

1.Large size, more needs

2.Not all cells are exposed to outer environment

LIFE PROCESSES (Introduction & Nutrition) PRETEST ANSWERS

So assuming that the reading pre test has been sincerely 😇 attempted, I'm today sharing the answers.
If you have not found time/interest to attempt the pre test before, make sure you do that before going through these answers.

1. Molecular movements are needed for life.

2.Energy for life processes is obtained through a process known as Nutrition.

3.Life on Earth depends on Carbon based molecules. (name of element)

4.The most common energy producing reactions in living organisms are oxidation - reduction reactions.

5.The maintenance processes such as nutrition, respiration & excretion are known as Life processes.

6.Besides plants, Bacteria are also capable of  autotrophic nutrition.

7.Breakdown of complex substances in to simple substances is done with help of bio-catalysts known as Enzymes.

8.Whittaker’s 2 groups that are essentially heterotrophs are Fungi & Animals.

9.Food reserve in plants is Starch, while in animals is Glycogen.

10. Leaves with 2 or more coloured patterns are known as Variegated leaves.

11.Opening and closing of stomata is controlled by Guard Cells cells.

12. N is taken in form of nitrates or nitrites from soil; or as organic N compounds prepared by Bacteria.

13. In Amoeba food is taken with the help of Pseudopodia_ while in Paramecium it is taken at a specific spot with the help of Cillia.

14. Watering of mouth is due to production of saliva which contains the enzyme Amylase.

15.  Contraction of muscles in inner lining of alimentary canal leads to movements known as Peristalsis.

16.  Small Intestine is the site of complete digestion in humans.

Self Assessment:

If you have managed ≥12 of 16, you are a good reader, and can easily proceed to next segment.

If you're between the range of 7-11, I suggest you read the pages from your NCERT once again before proceeding to the next segment.

If you're <7, make sure you work on your concentration skills.

LIFE PROCESSES: Reading & Pretest

PRE TEST NCERT pgs 94-100

1.____________ movements are needed for life.

2.Energy for life processes is obtained through a process known as __________.

3.Life on Earth depends on ____________ based molecules. (name of element)

4.The most common energy producing reactions in living organisms are __________________ reactions.

5.The maintenance processes such as nutrition, respiration & excretion are known as __________ processes.

6.Besides plants, ________ are also capable of  autotrophic nutrition.

7.Breakdown of complex substances in to simple substances is done with help of bio-catalysts known as ______________.

8.Whittaker’s 2 groups that are essentially heterotrophs are _________ & _________.

9.Food reserve in plants is _____________, while in animals is ____________.

10. Leaves with 2 or more coloured patterns are known as ____________ leaves.

11.Opening and closing of stomata is controlled by __________ cells.

12. N is take in form of nitrates or nitrites from_________; or as organic N compounds prepared by _____________.

13. In Amoeba food is taken with the help of _____________ while in Paramecium it is taken at a specific spot with the help of _____________.

14. Watering of mouth is due to production of _____________ which contains the enzyme ______________.

15.  Contraction of muscles in inner lining of alimentary canal leads to movements known as ______________.

16.  ________________ is the site of complete digestion in humans.

CLASS X

Welcome to the new session of 2019-20.

with compulsory Board for class X started in 2017-18, students appearing in 2019-20 Class X board examination have 2 years of experience and material available to them. The fear of unknown may have lessened a bit, but anxiety is completely justified. This would be the first time you would be appearing for an external examination. 

Preparation, thorough preparation is the only guarantee to success & the only strategy that can lessen your fears.

Though Biology would be a small part of your syllabus, approximately 1/3rd of science; but on an average 28-30 marks out of 80 of your science exam are from Bio portion.

Interestingly it is comparatively easier to score compared to Physics & Chemistry. It has been my experience that my students find it easier to comprehend & practice. Or may be I'm a good teacher 😉😇 

It would be my attempt in this year to cover the following lessons from class X Biology portion systematically & sequentially:

Chapter 6 Life Processes 

Chapter 7 Control & Coordination

Chapter 8 How do Organisms Reproduce

Chapter 9  Heredity & Evolution

Chapter 10 Our Environment

The strategy in each of the lessons would be:

• Divide the lesson in to specific 3-4 topics based on NCERT book. (we'll strictly keep NCERT as the base)
• A pre test would be uploaded on each topic on  weekly basis. The pretest would be a small objective type test of 15-20 questions.
• Prior to attempting pretest, you must read the pages on which the pretest is based. (the page numbers would be specified at the beginning of pretest).
• Reading of NCERT books thoroughly, line by line, is absolutely must. The pretest is to ensure that. Hence I insist on reading. 
• By class X, each one of you have sufficiently developed reading skills. the role of teachers should only be to :

Guide your learning

Clear Doubts if any

Provide Practice problems

• Next, I shall be uploading study material on the Topic. It'll have diagrams form NCERT, which you should draw & label.
• The study material would also have some retrieval questions which will help you to check your understanding.
• It is suggested that you can make Flash Cards, the flash cards can be assigned in to 3 groups:
• Gp 1 Material that you've become completely comfortable with.
• Gp 2 Material  you would need to rewise again
• Gp 3material you have doubts about or are totally unfamiliar with
• the gp 1 flash cards need to be revised after 4 days, gp 2 flash cards after 2 days, and gp 3 flash cards the next day.
• you can change the card gp based on your retention during revisions.
• Finally at the end of week an assignment would be given with value points based on CBSE pattern. You can solve the assignments and assess the same based on value points provided a day later.
• Finally to ensure proper benefit, a time schedule is essential. a half hour of undistracted & focused follow up should be sufficient. however some may need more or less time. I'll let you be the judge of that.

So we start with Chapter 6: Life Processes.

The chapter would comprise of the following sub parts:

• Introduction
• Nutrition
• Respiration
• Transport
• Excretion

Get set 👍👍 wish you all the very Best