MUTATIONS

“THE TRUTH IS OUTTHERE.”

“What’s in a gamete?”

A gamete is a cell that fuses with another cell in SEXUAL REPRODUCTION.

This means that the SPERM and EGG cells are both gametes.

GAMETES CONTAIN CHROMOSOMES

• A chromosome is an organized structure that contains DNA and Protein.

Chromosomes…

In each gamete there are 23 chromosomes.

This means that during sexual reproduction, when the gametes come together there should be a total of 46 chromosomes. But what if something goes… wrong?

What is a mutation?

“A mutation is a change to the base pair sequence of an organism.”

- www.wikipedia.com

Mutations

• While a mutation may be passed on to every cell that develops from the mutated cell, only mutations in sex cells may be passed on to the offspring.

• This shows that it is possible for mutations to be hereditary.

You get it…

Mutations continued…

• The effects of these “chromosomal alterations” are most likely to be visible in the phenotype. This is because there are a lot of genes involved.

• When a mutation occurs in body cells it will not continue on through/during sexual reproduction.

• Most mutations are harmful and recessive.• Most gene mutations are noticeable in the phenotype

but other might not be as noticeable.

Types of mutations…

1. In genetics, there is such a thing as deletion, and it is indeed a mutation. Deletion occurs when a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material. Causes could be breaking without rejoining, unequal crossing over, or losses from translocation.

continued…

• This is translocation, there are two types: reciprocal or robertsonian. Also, translocations can be “balanced or unbalanced (where the exchange of chromosome material is unequal resulting in extra or missing genes).”

- www.wikipedia.com

Gene Duplication

• any duplication of a region of DNA that contains a gene.

• it may occur as an error in homologous recombination

• Also a duplication of an entire chromosome

• Leads to multiple copies of chromosomal regions.

Non Disjunction

• Non disjunction is the failure of chromosome pairs to separate properly during meiosis or mitosis. Either a failure of homologous chromosomes to separate during meiosis I, or failure of sister chromatids to separate during meiosis II or mitosis.

Polyploidy is caused by nondisjunction

Disjunction

Disjunction is the seperation of homologous chromosomes during meiosis.

But, if disjunction fails to occur [non disjunction, remember?] then gametes with an additional or missing chromosome will be produced.

Hence mutation.

Polyploidy

The presence of one or more entire additional sets of chromosomes in an organism

Effects of Mutations

• Loss of function: Which is the result of a gene product have close to or no function at all.

• Gain of function: changes the gene product so that it gains a new abnormal function.

• Lethal Mutations: An organism carrying this will result in death.

Yikes.

Now Michael, what are the causes of mutations?• Well, the causes of mutations could be Radiation: x-

rays, ultraviolet, microwaves, cosmic waves.• Chemicals such as formaldehyde, benzene, asbestos

fibers, THC, nicotine [as found in ciggarettes]• The environment interacts with genes in the

development and expression of inherited traits.• The adaptive value of a gene mutation is dependent

upon the nature of the mutation and the type of environment with which the organism interacts.

Bibleography

•www.wikipedia.com• Images have either been taken

from www.wikipedia.com or www.images.search.yahoo.com

•There are direct quotes taken from Mrs. Ashkenazy’s “introduction to genetics notes.”

THE END