Science+102+Genetics


 * //In a moment of decision the best thing you can do is the right thing. The worst thing you can do is nothing.//**
 * //- Theodore Roosevelt -//**

LAST UPDATE ON: 29th MAY

The unit assessment (i.e. a test) for Genetics will be on June 3rd, Friday. Make sure you revise thoroughly using the notes, worksheets (listed below), homework and the textbook.





The answers for this worksheet can be found at the bottom of this page.. just keep scrolling down.























DNA (Deoxyribose Nucleic Acid) is the genetic material that is found in the nucleus of living cells. It is the chemical substance that codes for the characteristics of living things – e.g. hair colour The structure of DNA is like a twisted ladder. It is made up of: - sugar units - phosphate units - base units
 * __WHAT IS DNA?__**

The link below is to the youtube videoclip showing the structure of DNA. DNA structure

The link below is your most favourite song - the DNA song. Hip hip hooray for DNA! DNA song

This is a powerpoint presentation on the structure of DNA.

When an organism grows, repairs itself, reproduces or replaces old cells, new cells need to be made. Every new cells needs its own copy of DNA that is the same as the original. Making new copies of DNA is called __DNA replication__
 * __How is DNA Made?__** **__– DNA Replication__**

1. An enzyme called Helicase “unzips” the base pairs by breaking the bonds. 2. Raw materials are needed to “re-build” the two parent strands. 3. Another enzyme called DNA Polymerase is used to arrange nucleotides in a new complimentary strand.
 * __How does DNA replication occur?__**

The following links are the youtube videos clips showing how DNA replication occurs and how DNA mutation can happen when a thing or two goes wrong...

DNA replication DNA mutation

This is a well made powerpoint presentation on DNA replication.

This was the homework about the Treeman - the document includes the link.

This is the worksheet about Punnet Practice. The answers for this will be uploaded within this week (week 3).

__**Mitosis**__ Organisms grow and heal (repair) by producing new cells which are identical to the original cell. This is called Mitosis. Mitosis involves making an exact copy of the original cell’s DNA so two new identical cells called daughter cells can be produced. Mitosis takes place in every part of an organism – to grow and repair itself.

media type="file" key="Mitosis.flv" width="360" height="270"

__**Meiosis**__ The process of producing gametes (sex cells) is called meiosis. Meiosis produces 4 gametes each with only half the number of chromosomes. Occurs as a method of passing chromosomes (DNA, genes) from one generation to another. Happens only in the sex organs (ovaries and testicles).

media type="file" key="Meiosis.flv" width="360" height="270"

__**Crossover**__ media type="file" key="Crossover.flv" width="360" height="270"

__**Can you define these terms?**__

**Chromosome** - thread-like structures bearing genes that are found in the nucleus of a cell. Visible during the prophase of cell division. **DNA** - deoxyribose nucleic acid. A molecule found in the nucleus of cells which codes for an individual's genetic makeup. **Double helix** - a term used to describe the structure of DNA - 'twisted ladder' **Base** - One of four chemicals which make up the 'rungs' of DNA: Adenine, Thymine, Cytosine and Guanine. **Base Pair** - The two bases making up each 'rung' of DNA: either A-T or C-G **Nucleotide** - A molecule containing a sugar-phosphate-base, found in DNA. **Triplet** - A sequence of three nucleotides found on a DNA strand.

**Allele** – one of a number of possible forms of a gene. Each characteristic has two alleles. **Dominant allele** – an allele that controls the phenotype regardless of what the other allele is **Recessive allele** – an allele which is only expressed in the offspring if the dominant allele is absent **Genotype** – The combination of two alleles for a particular gene **Homozygous Genotype** – having two identical alleles for a particular gene; true breeding **Heterozygous Genotype** – having two different alleles for a particular gene; not true breeding **Phenotype** – the characteristic produced by the genotype **Gene** – a length of DNA carrying the code for one feature **Characteristic** – a distinctive inherited feature of an organism <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Inheritance** - The passing on of traits from generation to generation through the genetic code <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Pure Breeding** - Organisms homozygous for a trait. <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Selective Breeding** - A process that is used to breed for specific required traits.

<span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Sexual reproduction** - the form of reproduction involving the fusion of two gametes from two parents. Produces a variation in the offspring. <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Asexual reproduction** - reproduction of identical offspring from a single parent. No gametes are involved. <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Cloning** - a process that produces identical genetic individuals. <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Mutation** - a random change in the genetic code of an individual <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Variation** - the differences between individuals. <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**DNA replication** - The rpocess whereby DNA makes an exact copy of itself

<span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Gamete** - a sex cell <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Fertilisation** - the fusion (joining) of a male and a female gamete to form a zygote <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Zygote** - a fertilised egg.

<span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Cell Division** - The formation of two or more daughter cells from one original cell <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Meiosis** - The type of cell division which produces sex cells (gametes) <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 16px; text-align: start; text-decoration: none; vertical-align: baseline;">**Mitosis** - The type of cell division which produces two identical daughter cells from one parent cell

<span style="display: block; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 1788px; width: 1px;"> <span style="color: #fffbba; display: block; font-family: 'Comic Sans MS'; font-size: 40pt; text-align: center;">**__Mitosis__** Organisms grow and heal (repair) by producing new cells which are identical to the original cell. This is called Mitosis. <span style="color: #fffbba; display: block; font-family: 'Comic Sans MS'; font-size: 34pt; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 1788px; width: 1px;"> Mitosis involves making an exact copy of the original cell’s DNA so two new identical cells called **__daughter cells__** can be produced. <span style="color: #fffbba; display: block; font-family: 'Comic Sans MS'; font-size: 34pt; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 1788px; width: 1px;"> Mitosis takes place in every part of an organism – to grow and repair itself.