genes and dna

Genes And DNA

What is DNA?

Chromosomes and their genes are made of a molecule called DNA.

DNA molecules carry the code that controls what your cells are made of and what they do.

DNA stands for deoxyribonucleic

acid.

Each chromosome is a very long molecule

of tightly coiled DNA.

Which part of a DNA molecule holds this information?

What is DNA?

Structure of DNAStructure of DNA

DNA and base pairs

The rungs of the DNA ladder are made from pairs of bases.There are four types of bases.

These bases always pair together in the

same way.

How do you think the four bases pair up?

Adenine

Cytosine

Guanine

Thyamine

DNA and base pairs

DNA and base pairs

Base pairs hold the two strands of the DNA helix together.The rules for base pairing are…

There are millions of base pairs in a DNA molecule that always follow these rules.

A always pairs with T

C always pairs with G

Amazingly, it is the sequence of bases along a DNA molecule that forms the genetic code – it’s that simple!

DNA and base pairs

Known as Chargaff’s Rules

Build your own DNA moleculePracticeBuild your own DNA molecule

DNA – true or false?PracticeDNA – true or false?

DNA and cell division

What happens to the chromosomes when a cell divides during mitosis?

What must happen to DNA during this same process?

cell division

chromosomesare copied

Why must chromosomes be copied before a cell divides?

Making copies of DNA

DNA and cell division

A DNA molecule is able to make a copy of itself.

This is how chromosomes are copied before cell division.

DNA’s ability to copy itself means that all the genetic information is passed on to new cells.

How does a DNA helix make a copy of itself?


How does DNA copy itself?Making copies of DNA

The DNA molecule “unzips” as the rungs of the ladder separate and the molecule splits into two single strands.

How DNA copies itself

DNA can make copies of itself because it is double stranded.



Each single strand builds up into a new double strand. What do you notice about the new DNA molecules?

New bases from the cell move in and, following the pairing rules, match themselves to the bases on the single strands.

new DNA molecules



What is the copying of DNA also called?

The new DNA molecules are identical to each other and the original DNA molecule.

new DNA moleculesoriginal DNA molecule

replication


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PracticeBuild your own DNA molecule

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DNA multiple choicePractice!

What are proteins made of?How DNA works

Amino Acids• Organic compounds that combine to form proteins. • Are small, relatively simple chemicals made of

hydrogen, carbon, nitrogen, oxygen and sulfur. • There are 20 common amino acids:


Amino Acids and Proteins• Amino Acids (AA) can be attached to each other forming

an endless variety of larger molecules called proteins. • Each protein has a unique

sequence of AA. The number and order of AA is different for each type of protein.

• The different shapes and sequences give the proteins different functions, eg keratin is a fibrous protein found in hair and nails. Enzymes are also proteins.


Proteins and DNA• Each gene acts as a code, or set of instructions, for

making a particular protein. They tell the AA how to align in order to form the right protein shape.

• Proteins need to have the exact shape, be build in the exact moment and the right place in order to function properly.


A strand of DNA is extremely long and it is found coiled up in the nucleus of the cell. However AA needed to create proteins are placed in the cytoplasm.

RNA (Ribonucleic Acid) make partial copies of specific areas of the DNA.

RNA looks like DNA but is shorter and is missing one side. Since they are small, they can fit into tiny pores of the membrane of the nucleus out to the cytoplasm

In the cytoplasm, RNA goes to the ribosomes (proteins building machines) that read the code, 3 letters at a time, take AA from the surroundings, stick them together to form the protein according to the RNA code

How do genes make proteins?

Genes are made of DNA. Proteins are made of amino acids.

Each amino acid is coded for by its own special sequence of three bases called a triplet:

triplet amino acid

How DNA works


The amino acids join together to form a protein molecule.

Each gene contains the sequence of bases for one protein.

The order of triplets in a gene determines the sequence of amino acids.

Why is the sequence of bases in DNA called the genetic code?

How DNA works


The genetic code is the order of DNA bases which determines the sequence of amino acids in a protein.

How many triplets code for a protein of 20 amino acids? 1 amino acid = 1 triplet

20 amino acids = 20 tripletsHow many bases code for a protein of 20 amino acids?

How DNA works

Build your own protein moleculeHow DNA works

Build your own protein moleculeDNA vs RNA

• Deoxyribonucleic Acid • Double Helix

• Double Stranded• Deoxyribose Sugar

• Instructions for making proteins

• Nucleus

• Ribonucleic Acid • Single Helix

• Single Stranded • Ribose Sugar

• Copy the Instructions & make the proteins

• Nucleus, Cytoplasm, & Ribosomes

• Nucleic Acids• Helix

• Nucleotides • Sugar

• Phosphate • Bases

• Genetic Information

DNA RNA

DNA mutations and proteinsMutations

A mutation is a change in the nucleotide-base sequence of a gene or DNA molecule.

What cause a mutation?

MUTATIONS

Mutations are random

Types

• Sunlight

• Radiation

• Chemicals (smoking)

Mutagen

• Errors during DNA replication.

Can cause disease, developmental delays, structural abnormalities.

Advantageous can lead to an evolutionary advantage

Substitution Insertion Deletion

Repaired Become part of the genetic message

If the mutation occurs in the sex cells, the changed gene can pass from one generation to the next.


SUBSTITUTION INSERTION DELETION


SUBSTITUTION INSERTION DELETION When one or more bases in the sequence is replaced by the same number of bases (for example, a cytosine substituted for an adenine).

When a base is added to the sequence.

When a base is deleted from the sequence.

Can be really harmful because you modify all consequent reading (groups of three)

Genetic code quizPractice!

genes and dna

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