BIG QUESTIONS: 1.ARE ALL MUTATIONS BAD? EXPLAIN.. 2.CAN EVOLUTION OCCUR IN ABSENCE OF MUTATIONS?

BIG QUESTIONS:

1.ARE ALL MUTATIONS BAD? EXPLAIN..

2.CAN EVOLUTION OCCUR IN ABSENCEOF MUTATIONS?

Mutations

Mutations

• Errors in the DNA sequence that are inherited.

• Possible negative, positive or unknown side effects.

Types of Mutations

A) Silent Mutation (Point Mutation)• A single substitution of one base.• No change in the amino acid; therefore, no effect.• Occur in introns / non-coding regions of DNA.

Types of Mutations

B) Missense Mutation• A single substitution of one base.• Results in a different amino acid; therefore, different protein

is made.

Types of Mutations

C) Nonsense Mutation• A single substitution of one base.• Forms a premature stop codon; therefore, leading to the

formation of an incomplete polypeptide.• Often lethal.

Types of Mutations

Substitution Replaces a nitrogenous base pair

with another, different one. Silent / Missense / Nonsense

Insertion The addition of one or more extra

nucleotides in the DNA sequence.

Deletion The removal of one or more

nucleotides in the DNA sequence.

Leads to a change/shift in the reading frame (mRNA strand).

Types of Mutations

D) Frameshift Mutation• Causes changes in the reading frame.• Caused by an insertion or a deletion.

FRAMESHIFT MUTATION:

HEY MAN HOW ARE YOU BRO

and

HEY MAN HWA REY OUB RO(remove “O” in original HOW) or

HEY MAN HOQ WAR EYO UBR O(insert “Q” at W position in original HOW)

The resulting nonsense (or malformed protein) is a result of a random insertion

or deletion of information (nucleotides)

and our “frame”, the manner in which we interpret this information.

Types of Mutations

E) Translocation• The transfer of a fragment of

DNA between two nonhomologous chromosomes.

• Large segments of DNA can move from one location on the genome to another.

Types of Mutations

F) Inversion• The reversal of a segment of DNA within a chromosome (i.e.,

copied backwards).• No gain or loss of genetic information.• A gene may be disrupted.

Causes of Genetic Mutations

Spontaneous Mutations• Caused by errors in DNA replication.• DNA polymerase I rereads duplicated DNA for errors,

but it isn’t perfect…point mutations may result (insertion / deletion / silent mutation / missence mutation / nonsense mutation)

Causes of Genetic Mutations

Induced Mutations• Caused by mutagenic agents.• Mutagenic agents include UV radiation, cosmic rays,

X-rays and certain chemicals.

Nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.

Mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival.

BIG QUESTION:

How did “human like” traits such as a smaller jaw (relative to apes) and hairlessness pop up when they don’t appear in the wild in any real frequency?

Our diets changed and our brains got bigger, pressures that caused a smaller jaw.

Another way to look at this – what if our diets changed and our brains got bigger due to proto-human society adapting to mutation of the jaw?