Genetics

Chapter 20

Genetics

Study of HEREDITY Traits that are passed from parent offspring Sexual Repro. 2 parents, offspring is a

combo. This VARIATION leads to EVOLUTION

Asexual Repro. 1 parent, offspring is identical

Genetics Gregor Mendel“Father of

Genetics” 1800’s Worked with

pea plants Easy traits to

study

Vocab:Genetics: Study of heredity Heredity: Passing of genetic

info. from parent to offspring

Genes: Located on

homologous chromosomes

2 genes for each trait (1from mom, 1 from dad)

Units of heredity Determines

traits/characteristics

Hereditary Information DNA- DeoxyriboNucleic Acid… Organic (C, H, O, N) Double Stranded Organized in the form of genes on the

chromosomes found in the nucleus Genetic Recombination:Sperm & egg combine to form a zygoteThat organism has a complete set of

genetic info.

DNA

The DNA Molecule and Chromosomes

The Genetic Code

Structure was discovered by James Watson & Francis Crick

Model of DNA The Double Helix

A twisted ladder

Structure of DNA POLYMER –

long chain of repeating units called NUCLEOTIDES

A nucleotide contains: Phosphate Group Deoxyribose (sugar) Nitrogenous Bases

(Adenine, Thymine, Cytosine &Guanine)

Nucleotide

1. Phosphate group

2. Bond

3. Deoxyribose sugar

4. Bond

5. Weak hydrogen bond

6. Bond

7. A – adenine (base pair)

8. T – thymine (base pair)

9. G – guanine (base pair)

10. C – cytosine (base pair)

• Sides are made of Phosphate & Sugar that alternate

• “Steps” are made of NITROGENOUS BASES• SPECIFIC PAIRING:• A – T• C – G

– Hint: At GC or A Tall Cover Girl

• Weak Hydrogen bonds holds the bases together

Answer the Question:

• What would the sequence of the complimentary

strand be?

DNA Replication

• When a cell goes through MITOSIS • DNA of the cell makes a copy of itself

• 1. DNA UNRAVELS - unwinds• 2. DNA UNZIPS• 3. New nucleotides attach to template

strand• 4. Result: 2 identical DNA molecules

DNA Replication

DNA Replication:

DNA Replication

Mutations:

• Causes a change in the DNA code• Random• Can be increased b/c of radiation,

chemicals • If a mutation happens in a body cell

person is affected • If a mutation happens in a sex cell

offspring is affected

Mutation:

Types of Mutations:Original DNA Template:

CACCGTATTA1. Substitution: one base for another

CACCTTATTA2. Deletion: missing a base

CACCG ATTA 3. Addition: adding a base

CACCGTAATTA4. Inversion: bases are rearranged

CACCTAGTTA

Types of Genetic Mutations

What types of Mutations are these?

Answers:

1. Addition 2. Inversion3. Addition

Proteins & Cell Functioning

• Proteins Long chains of amino acids• Order of amino acids influences

the shape of the protein

• Proteins include: enzymes, insulin, eye color and hair

color

DNA-PROTEIN CONNECTION

• Genes contain genetic code

• This info. is used to make proteins that are required for its structure & function

• RIBOSOMES: make PROTEINS based on the

GENETIC CODE order of A, T, C, & G’s

RNA

• Ribonucleic Acid• Single stranded• Nitrogenous Bases:• A- Adenine• U- Uracil• C- Cytosine• G- Guanine

Types of RNA

1. Messenger RNA:• mRNA• Copies genetic

code from DNA • Brings code to

ribosome

2. Transfer RNA:• tRNA• Brings amino

acids to the ribosome so proteins can be assembled

Protein Synthesis• DNA is the code for proteins• Proteins are chains of amino acids

Steps of Protein Synthesis:

1. Begins in the nucleus with DNA2. DNA code is copied by mRNA3. mRNA brings code to ribosome4. tRNA brings AMINO ACIDS to

ribosome 5. amino acids are put together

making a protein

How did researchers make the connection between DNA and Protein?

Protein Synthesis and Sickle Cell

Karyotype- Picture of chromosomes

Needed to diagnose genetic disorders

Ex) Down’s Syndrome – Trisomy 21

DNA and Individuality Every cell in an organism has the SAME

DNA Each cell is different because it uses

different parts of the DNA The ENVIRONMENT influences gene

expression

Ex) Himalayan Rabbit

cold temp black fur

warm temp white fur

Ex) Freckles:

UV radiation from sun increases melanin in skin

Genetic Engineering

Genetic Engineering- Used to alter DNA in an organism.

1. Gene Splicing- Process that uses enzymes to cut and combine DNA from 2 organisms

Steps of Gene Splicing:Bacteria producing human insulin

1. Use enzyme to cut DNA from bacterial cell

2. Human DNA + Bacterial DNA are combined

3. Insert combined DNA into bacterial cell

4. Bacterial cell now produces human insulin

Gene Splicing Examples:

• Uses of gene splicing:1.Bacteria producing human insulin2.Plants with genes for insecticide (to kill

pests, prevent crop destruction)

Selective Breeding

1. Selective Breeding- Breed for the best traitsEx) Lean cowsEx) Large FruitsEx) Breeds of dogs