DNA, mRNA, and Protein Synthesis

TAKS Review

DNA stands for Deoxyribonucleic acid

Functions:◦ Store and transmit genetic info◦ Contains the blueprint for making proteins

What is DNA?

Location and Structure of DNA

Location:◦ Nucleus

Structure:◦ Double stranded, often called

double helix◦ Composed of three part

nucleotides: Deoxyribose (sugar) Phosphate (PO4) Nitrogen base (1 of 4):

Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Base Pairing Rule

During cell reproduction an exact copy of the parent cell is made

DNA unzips to make two new strands of DNA

Location: Nucleus

DNA Replication

DNA Replication

DNA contains the instructions for building proteins

Proteins are made at the ribosomes

DNA cannot leave the nucleus

How does DNA’s information get to the ribosome?

Making Proteins

Messenger RNA (mRNA)

What is mRNA?◦ Ribonucleic acid:

Single stranded Nucleotides composed of:

Ribose (sugar) Phosphate Nitrogen bases:

Adenine (A) Guanine (G) Cytosine (C) Uracil (U)

Transcription: RNA is made from a strand of DNA

Location:◦ nucleus

mRNA leaves the nucleus and takes the information to the RIBOSOME where a protein will be made

How does mRNA take DNA’s information to the ribosome?

Transcription

What happens to mRNA at the ribosome? mRNA will bind to

the ribosome

tRNA will read mRNA in three part sections (codon)

tRNA carries amino acids to the ribosome

Amino acids will bond to form a protein

Translation

Translation

Translation (continued)

Remember: mRNA is read in 3 part sequences called a codon (there are 64 total)

Every 3 part sequence codes for an amino acid

Proteins are determined by the order in which amino acids are joined together

There are 20 different amino acids which can combine to form many different proteins

Genetic Code-language of mRNA

Mutations – are changes in the genetic material.

2 Kinds:◦ Gene mutations◦ Chromosomal mutations

Mutations

Produce changes in a single cell. Types:

◦ Point mutations – involves changes in one or a few nucleotides and occur at a single point in the DNA sequence. Substitutions – one base is changed to another; only affects a

single amino acid. Insertions & Deletions– a base is inserted or removed from the

DNA sequence; much more dramatic because the genetic code is read in 3-base codons.

◦ Frameshift mutations – the shifting of codons & the “reading frame” which may change every amino acid that follows the point of the mutation. It can alter a protein so much that it is unable to perform its normal functions.

Gene MutationsSee pg. 307, Fig. 12-20

Substitution InsertionDeletion

Gene Mutations: Substitution, Insertion, and Deletion