Principles of Inheritance & Variation€¦ · Principles of Inheritance & Variation - Part III...

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Principles of Inheritance & Variation - Part I Sugar-phosphate double helix Base pair RNA RIBONUCLEIC ACID DNA DEOXYRIBONUCLEIC ACID Single-stranded genetic material Found in some viruses types depending on function: mRNA (messenger RNA) tRNA (transfer RNA) rRNA (ribosomal RNA) Sugar-phosphate helix Nucleobases Nucleobases GUANINE G ADENINE A CYTOSINE C NH2 N H O N THYMINE T H3C NH N H O O NH NH2 N H O N N H2N N H N N N GUANINE G ADENINE A CYTOSINE C NH2 N H O N URACIL U NH N H O O NH NH2 N H O N N H2N N H N N N G G G C C G G T T A A C C G C C G C G C G A U C Two Identical Chromatids One is exact copy of the other and each contains one DNA molecule Short arm structure Long arm structure Long string like DNA molecule formed into compact structures by proteins called histones. Constricted point of the chromosome p arm q arm DNA molecule Centromere Gregor Johann Mendel Proposed Laws of Inheritance Father of Modern Genetics Genetic Material Genetic Inheritance Most common genetic material, except in some viruses Double stranded genetic material Nucleotides create chain via phosphodiester bonds & nitrogen bases form hydrogen bonds DNA replicates by forming RNA intermediates

Transcript of Principles of Inheritance & Variation€¦ · Principles of Inheritance & Variation - Part III...

Page 1: Principles of Inheritance & Variation€¦ · Principles of Inheritance & Variation - Part III Linkage & recombination are the phenomena which describe the inheritance of genes €

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Principles of Inheritance & Variation - Part I

Sugar-phosphate double helix

Base pair

RNARIBONUCLEIC ACIDDNA

DEOXYRIBONUCLEIC ACID

  �Single-stranded genetic material

  �Found in some viruses

  ��� � � � � types depending on function:

mRNA (messenger RNA)tRNA (transfer RNA)rRNA (ribosomal RNA)

Sugar-phosphate helix

NucleobasesNucleobases

GUANINE G

ADENINE A

CYTOSINE CNH2

NH

O

N

THYMINE T

H3CNH

NH

O

O

NH

NH2

NH

O

N

N

H2N

NH

N

N

N

GUANINE G

ADENINE A

CYTOSINE CNH2

NH

O

N

URACIL U

NH

NH

O

O

NH

NH2

NH

O

N

N

H2N

NH

N

N

N

G

G

G

C

C

G

G

T

T

A

A

C

C

G

C

C

G

C

G

C

G

A

U

C

Two Identical ChromatidsOne is exact copy of the otherand each contains one DNA molecule

Short arm structure

Long arm structure

Long string like DNA molecule formed into compact structures by proteins called histones.

Constricted point of the chromosome

p arm

q arm

DNA molecule

Centromere

Gregor Johann Mendel

� ­ �� � � �� � � � �� � � � �

� ­ �� � � �� �� � � � � � � � � � � �� � � � � � � � � �

Proposed

Law

s of

Inhe

rita

nce

� ­ �� � � �� �� � � � � � � � � � �Father of Modern Genetics

� � � � � � � � � �� � � � �� �� � � � � � �� � � � � � � �� � � � � �� � � � � � � �� �� � � � � � � � �

Genetic Material

Genetic Inheritance

� � �� � � � � �� �� � � � � �� � � � � � � � � � �

Gregor Johann Mendel

� � � � � � � � � � � �� ���� � � �� � � � � � � � �

  �Most common genetic material, except

in some viruses

  �Double stranded genetic material

  �Nucleotides create chain via

phosphodiester bonds & nitrogen bases form

hydrogen bonds

  �DNA replicates by forming RNA intermediates

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F1 generation F2 generation

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In heterozygous condition, thedominant allele gets expressed. F1 generation express dominant alleles.

Two alleles do not mix when they come together in hybrid pair & are independent of each other.

During gamete formation, two genes segregate independently of each other as well as of the other trait

  �A monk who went to University of

Vienna to study science & Mathematics

  �1856 – 1863: Conducted experiments

on pea plant (Pisum sativum)

  �Studied the pattern of inheritance

  �Proposed laws of inheritance

  �Plants are easy to grow & maintain

  �Several visibly distinct & contrasting

characters

  �Annual plant

  �Naturally self-pollinating but can be

cross-pollinated

  �Genes exist as alleles that pass from parents to o�spring

  �Homozygous: 2 same alleles

  �Heterozygous: Di�erent alleles

  �Dominant gene: TT (capital alphabet); Recessive gene: tt (small alphabet)

  �Phenotype: Physical appearance

  �Genotype: Genetic makeup

  �50% chance of either allele to fuse with other parent to form zygote

  �Cross-pollinated 2 pure lines for contrasting characteristics to obtain F1 generation  �Self-pollinated F1 generation that gave rise to the F2 generation

Gregor Johann Mendel (1822 - 1884)

A monk who went to University of Plants are easy to grow & maintain

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Seven Contrasting Characters of Pea Plant Studied by Mendel

Results Conclusion

Laws of Inheritance

Mendel’s Experiment

FlowerColour

SeedColour

PodColour

FlowerPosition

SeedShape

PodShape

PlantHeight

DominantTraits

RecessiveTraits

Purple

Green TerminalWrinkledShortWhite

Pea plant(Pisum sativum)

All tall plantsTall Short Short

1 3

Yellow

Yellow Constricted(�at)

Round Green AxialIn�ated(full)

Tall

TT

Tt

Xtt

Parents

F1 generation

TT

Tt

Xtt

TT Tt Tt tt

Parents

F1 generation

Parental (P)generation

F1 generation

Gametes

RrYy

x

rryyRRYY

ryrYRyRY

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Principles of Inheritance & Variation - Part II� � � � � � � � � � � � �� �� � � � � �

Gregor Johann Mendel

Page 3: Principles of Inheritance & Variation€¦ · Principles of Inheritance & Variation - Part III Linkage & recombination are the phenomena which describe the inheritance of genes €

Morgan’s Experiment

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Crossing over

Principles of Inheritance & Variation - Part III

Linkage & recombination are the phenomena which describe the inheritance of genes

  �Two or more linked genes are always inherited together in the same combination for over two generations

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Homologous chromosomes

aligned

ABC

ABC

ABC

ABC

ABC

abc

abc

abc

abc

abc

Chromosomescrossover

Recombinantchromosomes

Non-recombinantchromosomes

Parental phenotypes

Total ParentalPhenotypes: 1,541

Total recombinantPhenotypes: 900

Total progeny: 1,541 + 900 = 2,441Percent recombinants: 900/ 2,441X 100 = 36.9

white eyesminature wings

white eyeswild type wings

wild type eyesminature wings

white eyesminature wings, o+

F1 phenotypes

o+ wild type

wild type

F2 phenotypes

wild type �

white eyesminature wings, �

Total: 750

o+ 359 391�

Total: 791

439 352o+ �

Total: 455

218 237o+ �

Total: 455

235 210o+ �

w mw m( ) w+ m+

( )

whitewhite

Sex Determination: System that decides the sexual characteristics of an organism

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Male: XXFemale: XY

Female: ZW Male: ZZ

Mutation & Chromosomal Disorders: Major drawbacks of genetic inheritance

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