Genetic Variation

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what is a pedigree chart?

A pedigree chart is a chart of the genetic history of family over several generations . It is a record of the family of an individual.

What is a punnett square?

A Punnett square represents the possible(predict) FERTILISATION of gametes that occur between a male and female parent.

During Fertilisation( the fusion of male and female gametes)

it is RANDOM which male gamete will fetilise the female gamete

AND

For every fertilisation that occurs this has no effect on the next fertilisation.

SEXUAL REPRODUCTION

Definition:

Involves sex cells (gametes) and fertilization.

Involves two parents.

Advantages/Disadvantages:

offspring are not genetically identical to one another.

There is variation in the offspring (e.g. the offspring/baby will look like a MIX of both parents).

Examples:

Hibiscus Flower

Rose Flower

Peace lily flower.

Asexual Reproduction

Defintion:

Does not involve sex cells and fertilisation

only one parent plant.

Advantages/Disadvantages:

offspring have no variation

offspring are genetically identical to one another(i.e. the offspring /baby will look EXACTLY like the parent)

Examples:

Tuber e.g. patato, kumara

Bulb e.g daffodil, onion

Runner e.g. strawberry plant, spider plant.

Genetic Variation in a population is important because if there is a change in the enviroment some individuals will survive ( those with the better suited phenotype.

Why is DNA important?

DNA is important because it provides the information for the cells or a living organism to use.

The sequence of bases on each strand of DNA forms the genetic code.

The genetic code is used by the cells to determine the characteristics of an organism.

The Genetic code is made of DNA bases and triplet

Living cells read the genetic code to create the characteristics of a unique organism.

A unique organism made up of cells has unique characteristics.

The replication of DNA begins when the molecule unwinds and the bas pairs seperates . Each strand then acts as a template for a new strand. New matching DNA join to create base pairs to form the new bases moloecule.

What is the relationship between DNA, Alleles,Genes,Chromesome and Characteristics?

Another word for characteristics is trait. The particular characteristics or trait we display is calle ourphenotype.

Each organism has two versions of each chromesome. One comes from each parent. So chromesomes are said to come in pairs.

Humans have 46 chromesomes. We therefore have 23 pairs, one set coming from each parrent.

The main reason that we are slightly different from each other is that there are slightly different versions of every gene. These versions are called alleles. We have two alleles for each characteristics. The allels we inherit from our parents determine our characteristics because different alleles code for slight differences in how characteristics show up.

Our particular combination of alleles is called our phenotype

Meiosis

the process of producing gametes is called meiosis

DNA replication is essential for this process,

How does our genetic code make us look like we do?

The sex chromesomes come from each parent. They determine the sex of an organism . The male human is the one who determines the sex of any child, depending if the sperm is carrying an X or a Y sex chromesome.

XX codes for a female

XY codes for a male

Females can only give X to their children. Males can give and X or Y a 50:50 chance of being one sex of the other.

Our sex is determined by 1 pair of chromesomes- these are called the sex chromosomes and are given the labels X and Y.

What is Variation and How Does it Occur?

Variation are the natural differences that occur between different organisms. Variation occurs even within the same species .

These variation are due to slight differences in the genetic code.

Variation occurs due to two processes sexual and mutation.

some variation is due to sexual reproduction, as offspring always differ slightly from their parents.

Now alleles arise through a process called mutation e.g. baldness is due to mutation in several genes from one or both

Why is Variation

Important?

some combinations of alleles create phenotypes that provide a survival advantage for the individual.

A group of one species living in one area is called population. There can be variation of phenotype both within and between population.

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