Life Science - DNA: Code Of Life

What are the two types of nucleic acids found in a cell?

DNA and RNA

What are nucleic acids made of?

nucleotides

What do ribosomes do?

synthesize proteins

Where is DNA located in a cell?

In the nucleus as part of the chromatin network.
In mitochondria (mitochondrial DNA)
In chloroplast (plants)

Extra-nuclear DNA

DNA found outside of the nucleus: mitochondrial and chloroplastic DNA

Nucleus function

Control center of the cell

Who used X-ray diffraction to study the structure of DNA in 1952?

Rosalind Franklin and her assistant Maurice Wilkins.

Who proposed the double-helix model of DNA in 1953?

James Watson and Francis Crick

When did Watson and Crick receive the Nobel Prize for their discovery of DNA's structure?

In 1962.

What is the structure of DNA?

double helix

A nucleotide consists of

sugar, phosphate group, nitrogenous base

What makes up the sides of the DNA ladder?

deoxyribose sugar and phosphate

What are the four types of nitrogenous bases in DNA?

Adenine, Thymine, Guanine, Cytosine

Which nitrogenous base always pairs with Adenine (A)?

Thymine

Which nitrogenous base always pairs with Guanine (G)?

Cytosine

Pyrimidines

Cytosine and Thymine

Purines

Adenine and Guanine

What type of bonds hold the nitrogenous bases together in DNA?

weak hydrogen bonds

What is meant by one DNA strand being the complement of the other?

The sequence of bases on one strand determines the sequence on the other strand

What are the two primary functions of DNA?

DNA makes up genes that carry hereditary information and contains coded information for protein synthesis.

Exons

coding regions

Introns

non-coding regions

DNA replication

the process during which a DNA molecule makes an exact copy (replica) of itself

When does DNA replication occur?

Interphase

DNA replication steps

1. DNA double helix unwinds
2. Weak Hydrogen bonds between nitrogenous bases break and the 2 strands move apart
3. Each strand now acts as a template
4. Each single strand picks up free nucleotides from the nucleoplasm and becomes double again
5. The two strands are identical to each other and the original
6. Each double strand now becomes twisted and helical in structure

Why is DNA replication important?

It doubles the genetic material so that each cell receives the same amount of DNA during cell division and ensures the formation of identical daughter cells during mitosis.

What is a DNA profile?

a pattern of black bars that represents the DNA fragments of a person.

Uses of DNA profiling

To trace missing persons
To establish paternity
To match organ donors
To identify Genetic disorders

Where is RNA found?

mRNA is formed in the nucleus and functions in the ribosome
tRNA is located in the cytoplasm

mRNA

messenger RNA

tRNA

transfer RNA

What is the structure of RNA

single stranded molecules consisting of nucleotides

Three components of RNA nucleotide

1. phosphate
2. sugar - ribose
3. nitrogenous base

What are the nitrogenous bases in RNA

Adenine, Uracil, Guanine, Cytosine

Codon

group of 3 nucleotide bases in mRNA that specify a particular amino acid to be incorporated into a protein

Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

Function of RNA

plays a role in protein synthesis

Transcription in Protein Synthesis

Double helix DNA unwinds
The double-stranded DNA unzips when weak hydrogen bonds break to form 2 separate strands
One DNA strand acts as a template to form mRNA
Free RNA nucleotides from nucleoplasm attaches to DNA template to form mRNA.
mRNA now has the coded message for protein synthesis
mRNA moves from the nucleus to the cytoplasm and attaches to the ribosome.

Translation in Protein synthesis

Each tRNA carries a specific amino acid
When the anticodon on the tRNA matches the codon on the mRNA, then the tRNA brings along its corresponding amino acid
Amino acids become attached by peptide bonds to form the required protein