Unit 2 - DNA

Taken from chapter 9 of the textbook

What does DNA stand for

Deoxyribonucleic acid

What is DNA

A molecule found in almost all cells that carries genetic information for cell structure and function.

Where is DNA located?

In the nucleus where it holds nuclear DNA, and in the mitochondria where it holds mitochondrial DNA.

What is the structure of DNA

It is made up of a chain of repeating units called nucleotides, and has a double helix structure. It consists of rungs made up of nucleotides paired together.

What are nucleotides

Consist of 3 parts, phosphate group, a sugar molecule, and one of four nitrogenous bases such as adenine, thymine, cytosine and guanine.

What is the length of DNA in cells

2-3 metres long

Why is the length of DNA so long

It is wrapped around 8 proteins called histones to form nucleosomes that are then stacked on top of each other and then tightly coiled into chromatin.

What is mitochondrial DNA

A circular molecule not bound to histones.

What is the purpose of mitochondrial DNA

It plays an important role in coding for transfer RNA and enzymes needed for cellular respiration.

Structure/Build Up of Mitochondrial DNA

Has 37 genes essential for mitochondrial function, some code for tRNA others code for enzymes involved in cellular respiration.

What is the purpose of tRNA

It is used in protein synthesis

What enzymes carry out DNA replication

Helicase and polymerase

What occurs in the Helicase phase

Helicase unwinds the double helix and separates the two strands by breaking the hydrogen bonds that exist between the complementary base pairs. The two separated strands act as templates for the synthesis of new complementary strands.

What occurs in the Polymerase phase

Polymerase synthesises new strands from the two parental strands by aligning free nucleotides opposite their complementary base partner.

What is a protein

A large complex molecule made up of one or more long chains of amino acids.

What is the function of a protein

They have many functions such as forming transport structures, enzymes for specific tasks, protecting the body and more.

How many purposes does proteins have

3

What is the 1st purpose of a protein

Essential for building and repairing tissues, catalysing biochemical reactions as enzymes, and supporting immune functions as antibodies.

What is the 2nd purpose of a protein

Play crucial roles in transporting molecules, regulating hormones and enabling muscle movement.

What is the 3rd purpose of proteins

Help maintain fluid balance and can serve as a nutrient source when needed

How are proteins created from DNA

Protein synthesis

What is protein synthesis

The process by which cells build proteins.

What are the two main stages of protein synthesis

Transcription and translation

What are the stages of transcription

Unwinding DNA, making mRNA, processing mRNA and mRNA to ribosomes

What occurs in the first phase of transcription called unwinding DNA

The DNA in the cells nucleus unwinds and unzips in the area of the gene that needs to be copied.

What occurs in the second stage of transcription called making mRNA

An enzyme called RNA polymerase reads the DNA strand and creates a matching mRNA strand. mRNA is like a photocopy of the gene’s instructions.

What occurs in the third stage of transcription called processing mRNA

Before mRNA leaves the nucleus it gets a ca[p and a tail added for protection removing any unnecessary parts like introns

What occurs in the fourth stage of transcription called mRNA to ribosome

mRNA moves from the nucleus to the ribosome in the cytoplasm. The ribosome is like a factory that makes proteins

What are the stages of translation

Reading mRNA, bringing amino acids, building the protein, and finishing up

What occurs in the first stage of translation called reading mRNA

The ribosome reads the mRNA in groups of three bases called condons. Each codon codes for a specific amino acid.

What occurs in the second stage of translation called brining amino acids

Transfer RNA molecules bring the correct amino acids to the ribosome. Each tRNA has an anticodon that matches the mRNA codon.

What occurs in the third stage of translation called building the protein

The ribosome links the amino acids together in the correct order to form a protein chain.

What occurs the fourth stage of translation called finishing up

When the ribosome reaches a stop codon on the mRNA, the new protein is released and folds into tissue final shape to become functional