Intro to Genetics (2003)

7/31/2019 Intro to Genetics (2003)

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What is genetics?

The scientific

study ofheredity


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Gregor Mendel

Born in 1822 inCzechoslovakia.

Became a monk at amonastery in 1843.

Taught biology andhad interests in

statistics.Also studied at theUniversity of Vienna


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Mendel continued

After returning to the

monastery he

continued to teachand worked in the

garden.

Between 1856 and

1863 he grew andtested over 28,000

pea plants


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Mendels Peas

Easy to grow.

Easily identifiable traits

Can work with large numbers of

samples


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Mendels experiments

The first thing Mendel did was create apure generation or true-breeding

generation.He made sure that certain pea plantswere only able to self pollinate,eliminating unwanted traits.

He did this by cutting away the stamen,or male part of each flower


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Genes and dominance

Trait: a characteristic

Mendel studied seven of these traits

After Mendel ensured that his true-breeding generation was pure, he thencrossed plants showing contrasting

traits.He called the offspring the F1generation or first filial.


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What will happen when pure

yellow peas are crossed with

pure green peas?All of the

offspring were

yellow.Hybrids= the

offspring of

crosses betweenparents with

contrasting traits


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What did Mendel

conclude?Inheritance is determined by factors

passed on from one generation to

another.Mendel knew nothing about

chromosomes, genes, or DNA. Why?

These terms hadnt yet been defined.


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What were Mendels

factorsThe factors that Mendel mentioned

were the genes.

Each gene has different forms calledalleles

Mendels second principle stated that

some alleles are dominant and someare recessive.


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Mendels second cross

He allowed the F1 generation to self-

pollinate thus producing the F2

generation.Did the recessive allele completely

disappear?

What happened when he crossed twoyellow pea hybrid (F1) plants?


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Results:

of the peas were yellow, of

the peas were green.During the formation of the sex cells orgametes, the alleles separated or

segregated to different gametes. (pollen

and egg)


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Probability

The likelihood of a

particular event

occurring. ChanceCan be expressed

as a fraction or a

percent.

Example: coin flip.


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Punnett Square

Developed by

Reginald Punnett.

A diagram used toshow the probability

or chances of a

certain trait being

passed from onegeneration to

another.


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Reading Punnett

squaresGametes are placed above and to the

left of the square

Offspring are placed in the square.

Capital letters (Y) represent dominant

alleles.

Lower case letters (y) represent

recessive alleles.


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Punnett square example


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Homozygous= when an organism

possesses two identical alleles. ex.

YY or yy

Heterozygous= when an organism

possesses different alleles. ex.

Yy


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Phenotype vs genotype

Genotype

The genetic makeup

Symbolized withletters

Tt or TT

Phenotype

Physical

appearance of theorganism

Expression of the

trait

Short, tall, yellow,

smooth, etc.


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Probability and

statisticsNo one event has a greater chance of

occurring than another.

You cannot predict the precise outcomeof an individual event.

The more trials performed, the closer

the actual results to the expectedoutcomes.


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Punnett square review:


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Mendels death

Mendel published his paper on heredity

in 1866.

The scientific community saw little if anyimportance in his work.

Mendel died in 1884 with no recognition

for his contributions to genetics.


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Assignment:

worksheet

Pages 283-284

1-10, 13, 14, 17, 18, 24


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THE END

THANK YOU

ANDGOD BLESS US ALL ! ! !

GLENN CAGAS JAMODIONG

BSEBIOLOGY

Intro to Genetics (2003)

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