Genetics: Study of Heredity - PowerPoint PPT Presentation

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Genetics: Study of Heredity. Aim: What is Genetics?. Sexual Reproduction:. Two parents Half of the genetic information is received from one parent, half from the other. Variation  Evolution. Asexual Reproduction:. One parent

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Genetics: Study of Heredity

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Genetics study of heredity l.jpg

Genetics: Study of Heredity

Aim what is genetics l.jpg

Aim: What is Genetics?

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Sexual Reproduction:

  • Two parents

  • Half of the genetic information is received from one parent, half from the other.

  • Variation Evolution

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Asexual Reproduction:

  • One parent

  • Offspring is identical to parent.

  • Clones- identical genetic copies.

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  • Gregor Mendel- 1800’s

  • “Father of Genetics”

  • Pea plants: easy to grow

  • Contrasting traits

  • Easily self and cross pollinate.

  • From his studies, Mendel arrived at conclusions that are the basis for genetics today!

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Additional Vocabulary

  • Genetics: Study of heredity

  • Heredity: Passing of genetic information from an organism to it’s offspring.

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  • Genes: units of heredity

    • Determines traits/ characteristics an offspring will have.

    • Located on chromosomes.

    • For each trait-> minimum of 2 genes. One from mom, one from dad.

  • There are many genes located on a Chromosome.

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Hereditary Information:

  • DNA- deoxyribonucleic acid

  • Organic (C, H, O, N, P).

  • Double stranded

  • Organized in the form of genes located on the chromosomes.

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Hereditary Information:cont.

  • Homologous chromosomes- are same size and shape (one from each parent)

    • This allows for crossing over and variation to occur.

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Genotype vs. Phenotype:

  • Genotype- genes

  • Ex: B,b,S,s

  • Phenotype-Physical appearance

  • Ex: Fur Color, Fur Length

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Genetic Recombination:

  • Sperm and egg combine to form a new cell.

  • New cell (offspring) has a complete set of genetic information (DNA). Each offspring is unique.

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Structure of DNA was discovered by 2 scientists:

1953 James Watson and Francis Crick

Created a model known as the Double Helixa twisted ladder.

The Genetic Code:

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What is the structure of DNA?

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Structure of DNA

  • Long chain of repeating units ( polymer) called nucleotides.

  • A nucleotide unit contains:1. phosphate group O2. deoxyribose (sugar)3. nitrogenous base:

    • A- adenine

    • T- thymine

    • C- cytosine

    • G- guanine

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Structure of DNA

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One Strand of DNA


  • The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts.

  • The teeth are nitrogenousbases.



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Two Stranded DNA

  • Remember, DNA has two strands that fit together something like a zipper.

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A= adenine

G= guanine

C= cytosine

T= thymine

Types of nitrogen bases

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Structure of a Double Helix

  • Sides of the “ladder” are alternating phosphate group and deoxyribose sugar.

  • “rungs” of the ladder are made of 2 nitrogenous bases.

  • Specific pairings:

    • There is a weak Hydrogen bondBetween the base pairs.

    • Structure as a double helix

    • When a cell goes through mitosis(cell division) the DNA must also make a copy of itself.

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The earth is 150 billion m

or 93 million miles from

the sun.

DNA by the numbers

  • Each cell has about 2 m of DNA.

  • The average human has 75 trillion cells.

  • The average human has enough DNA to go from the earth to the sun more than 400 times.

  • DNA has a diameter of only 0.000000002 m.

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Aim: How does DNA replicate?

Do Now: Please answer the questions on the handout found on the front desk, omit questions 5-7.

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Genetics Can Tell All





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Base Pairing

  • Which bases always match up?

  • A-T

  • G-C

  • Adenine always binds with Thymine

  • Cytosine always binds with Guanine

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1.DNA unwinds

2. DNA unzips

3. Old strands become templates for new strands

4. Result- 2 identical DNA molecules

Steps of Replication:

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Characteristics of a Double Helix

  • Proteins and Cell Functioning:

    • Proteins- long chains formed from 20 kinds of amino acids.

    • Sequence(order) of the amino acids influences the shape of the molecule.

    • Proteins include: enzymes, insulin, eye color, and skin color.

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DNA- Protein Connection:

  • Genes contain coded information.

  • This information is used to make proteins that are required for it’s function and structure.

  • Ribosomes construct proteins based on the cell’s DNA code (combo of A, C, T, G’s).

  • Parent and offspring produce similar traits that is why there is resemblance between them. They produce similar proteins.

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Aim: How does protein synthesis Work?

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Protein Synthesis:

  • The building of protein molecules.

  • Synthesizing protein from DNA.

  • Proteins are chains of amino acids.

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  • Begins in the nucleus with DNA.

  • DNA code is read by a “ messenger molecule” messenger RNA; ;

  • mRNA.

  • “messenger molecule: travels into the cytoplasm of the cell to the ribosome.

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Steps cont.:

  • With the help of “transfer molecules” tRNA amino acids move to the ribosomes to make proteins.

  • The ribosomes “reads” the code and a chain of amino acids is produced forming a protein.

  • ***Protein structure is determined by DNA***

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  • Ribonucleic Acid

  • Single stranded

  • Nitrogenous bases

    • A- adenine

    • U- uracil

    • C- cystosine

    • G- guanine

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Types of RNA

  • Messenger RNA (mRNA)Copies code from DNABrings to ribosome

  • Transfer RNA (tRNA)Brings amino acids to ribosome for protein assembly

  • Mutations:Alteration of DNA sequence.Causes a change in code carried for by the gene.Random, but can be increased because of chemicals, radiation.

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Aim: What are different genetic mutations?

  • Do Now: Please complete the handout on the front desk.

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Different Types of Mutations:

  • Original DNA Template C A A T G C T A C

    • 1. Substitution: one base pair for another.C A A C G C T A C

    • 2. Deletion: missing a base.C A A T O C T A C

    • 3. Addition: adding an extra baseC A A T A G C T A C

    • 4. Inversion: bases are rearranged.C A G A T C T A C

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Causes of Mutations

  • Environmental Conditions can affect how genes are expressed.

    • Ex. Himalayan rabbit

    • Warmer body temperature white fur

    • Colder body temperature black fur

  • ** Identical twins- separated- different personalities

  • Chemicals, hormones can activate a gene, causing certain proteins to be produced.

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Genetic Engineering

  • Used to alter instructions in organisms.

  • Produce more desirable traits.

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Selective Breeding:

  • Produces animals and plants with desirable traits.

  • Horse & donkey= mule. (outbreeding)

  • Ex. Larger, juicier fruits…

  • Pure dog, pure cat. (inbreeding)

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Inbreeding/ Outbreeding

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Breeding continued:

  • ** In sexually reproducing organisms only mutations found on sex cells can be inherited by the offspring.

  • Mutations occurring in body cells will only affect that organism.

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DNA and Individuality:

  • The order of the nitrogenous base pairs, A,T,C,G’s are what makes each person an individual and unique. This is because the order allows for certain proteins to be produced.

  • In an organism every cell contains the same genetic code.

  • However, each cell is different: hair cells, skin cells, liver cells, stomach cells.

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Gene Expression.

  • Each cell only uses some of the genetic information from the chromosomes.

  • Certain parts of the chromosomes get “turned on” or “turned off.”

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Gene Manipulation:

  • Altering genes using enzymes

  • By manipulating the DNA in plant cells or animal cells; favorable offspring can be produced

  • Produce bacteria that can be beneficial.

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  • Cut DNA segment with enzymes

  • This segment can be spliced (moved) and attached to DNA of a new organism.

  • New organism will make the protein coded for by DNA code.

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Gene Manipulation

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Apply technology to biology.

Applications of Biotechnology:

By using gene therapy and applying it to modern medicine scientists may:

Produce hormones, enzymes and other body chemicals.

Provide at a low cost.

Provide a purer form.


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