1GENETICS

                                                                       

                                         

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What is Genetics?

• The study of how traits are inherited through the interaction of alleles

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Heredity

• The passing of traits from parent to offspring

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The Father of Genetics:Gregor Mendel

• An Austrian monk who studied mathematics and science

• Studied how traits pass from generation to generation

• He thought it was possible to predict the kinds of flowers and fruit a plant would produce

• Most of his work was done studying peas

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Gregor Mendel

• Mendel was the first to trace one trait through several generations

• He also used mathematics and probability to explain heredity.

• He is famous for his work with pea plants. Why did he choose peas?

• The conclusions he came to was how traits pass from one generation to the next

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1Genetics of Pea Plants

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Mendel’s Experiments• Peas…..• Purebred: parents always produced

the same traits generation after generation– Example: tall pea plants

• Crossing two plants with different expressions of the trait he found the new plants all looked like one of the parents

• He called these HYBRIDS– Example: yellow and green purebreds

produce all green peas

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Principles Of Heredity

1. Traits are controlled by alleles on

chromosomes2. An allele may be dominant or

recessive3. When a pair of chromosomes

separates during meiosis, the different alleles for a trait move into separate sex cells

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Genes

• located on chromosomes, -made up of DNA

• control an organisms form and function

• during meiosis, pairs of genes separate and each sex cell winds up with one form of a gene for each trait

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Alleles• Different forms of a trait that a

gene may have• Every sex cell has one allele for

each trait• Example…. Earlobes

Attached vs. Unattached

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Alleles separate into separate sex cells during meiosis

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Dominant / Recessive Traits

• Dominant factor- trait that dominates or covers up short form (Use Upper case letter)

• Recessive factor- trait that seems to disappear (Use lower case letter)

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Alleles Determine Traits

• Homozygoustwo alleles for a trait that are

exactly the same TT or tt

• Heterozygous

two different alleles for a trait

• Tt

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Genotype

We use letters to represent the trait or alleles.Example: Bb (heterozygous black) tt (homozygous short)

The set of genes an organism has. Sometimes it refers to the entire Genome of an organism and sometimes it refers to the alleles.

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Phenotype

• Physical trait that shows as a result of a particular genotype

• Example: curly ears• straight ears

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Punnett Square

• A tool used to predict results in genetics

• Dominant allele….Capital letter (T)• Recessive allele….small letter (t)• The letters that represent the

genetic make up are called: genotype

• Example: Tt

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Making a Punnett Square• The letters indicating the alleles

donated by each parent are written along the top and side. One letter per box.

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Probability• A science that helps you predict

the chance that something will occur

• Coin toss 50/50 probability• Studying large numbers increased

Mendel’s chances of seeing a pattern

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Sex Determination

• Females produce eggs that have only an X chromosome (XX)

• Males produce both X-containing sperm and Y-containing sperm (XY)

• Sex of an offspring is determined by the male gamete since males have both the X and the Y chromosome

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Boy or Girl?

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• “Blended” or intermediate expression

• Neither allele for a trait is dominant over another..both are expressed

• red and white flowers produced Pink flowers

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CR CW

CRCW

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Codominance

When 2 dominant alleles are expressed at the same time

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Multiple Alleles• Many traits are controlled by more

than two alleles, or multiple alleles.

• Blood types: A, B, AB and O• A and B are Dominant over OHuman BLOOD TYPES

Phenotype Genotype A AA or AO B BB or BO

AB AB O OO

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Polygenic Inheritance• Polygenic inheritance - a group

of gene pairs act together to produce a single trait

• Produces a wide variety of phenotypes– height– weight– body build– shape of eyes, lips and ear

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Mutations• Changes or errors that occur when DNA is

copied inside a cell.– Chemicals, radiation and radioactive substances

can also cause mutations• A mutation results in the change of genes• Mistakes in meiosis can result in an

organism with more or less chromosomes than normal.

• Incorrect chromosome number can cause chromosome disorders– Downs syndrome (an extra chromosome #21)

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Environmental Impact• Gene expression can be influence by

the environment– people at risk for skin cancer should avoid

sun exposure– Himalayan rabbits can only express the

allele for dark fur in low temperatures

                                   

         

                                   

         

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Recessive Genetic Disorders

• Occur when both parents pass on the recessive allele and both recessive allele must be inherited by the offspring

–Cystic Fibrosis–Sickle Cell Anemia

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Sex-linked Disorders

• Color-blindness• inherited allele on the X

chromosome that prevents from seeing certain colors

An allele that is inherited on a sex chromosome

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More Sex-linked Disorders

• Hemophiliablood does not clot properly

• Females are just carriers

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PedigreeA tool for following a trait through generations of a family

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Importance of Pedigrees• Pedigrees are important tools

geneticists use to understand how a trait is inherited

• They can then predict the probability the offspring will be born with a trait

• Extremely important in breeding animals or plants because livestock and plant crops are used as sources of food

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Genetic Engineering

• Scientists are experimenting with methods that allow them to go into cells to change or the arrangement of DNA

• Used to produce large quantities of medicine, such as insulin

• Also used to find new ways to provide people with more nutritious food

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Genetic Engineering

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Gene Therapy• Placing a normal allele in a cell that has

a mutation

• A virus is used

as the vector to

deliver the DNA

SELECTIVE BREEDING

The selection of certain seeds or animals for reproduction in order to influence the traits inherited by the next generation.

SELECTIVE BREEDING

• The Liger is the result of breeding a female Tiger to a male Lion.

• The liger has both stripes and spots. The stripes are inherited from its tiger parent and the spots from the lion parent.

The Zebroid is the result of breeding

a female Horse and a male Zebra.

The Zedonk / Zonkey is the result of

breeding a female Donkey and

male Zebra.

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OKAPI

Not selective breeding

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The Human Genome Project

• identify all the approximately 20,000 - 25,000 genes in human DNA,

• determine the sequences of the 3 billion chemical base pairs that make up human DNA,

• store this information in databases, • improve tools for data analysis, • transfer related technologies to the private

sector, and • address the ethical, legal, and social issues

(ELSI) that may arise from the project. • Work is still on-going