Additional Biology Smart Teach 1: DNA

Key terms used in exam questions Haploid – Half the chromosome number. Diploid – Full chromosome number. Gamete – Sperm and egg. Fertilisation– The fusion of a sperm and an egg to produce a zygote. Zygote – Cell with DNA from sperm and egg cell.

DNA What is the structure of DNA? Double helix With base pairs Held together by hydrogen bonds What is the function of DNA? To give instruction To make proteins Where is DNA found in an animal/plant cell? In the nucleus

DNA Base pairs match up: Guanine -- Cytosine Adenine – Thymine A good way to remember... Apple-Tart and Chocolate-Gateau Hydrogen bond between the base pairs

Scientists involved in structure of DNA Rosalind Franklin – Used X ray crystallography to study the structure, how the strands were arranged and the base pairs. Watson and Crick – Used Franklin’s work and were awarded the Nobel Prize for making a model of DNA. This has appeared as a long answer (6 mark) question.

Now lets have a look at an exam questions about this

*(b) Describe the structure of DNA, including the roles of the scientists involved in its discovery. (6) Using the information you have written down from the previous slides, answer this exam question.

Did you get these points into your answer? A description including some of the following points in a logical sequence Points relating to DNA structural features: ·two strands ·double helix ·(contains) bases ·A, T, C, G ·adenine / A paired with thymine / T ·guanine / G paired with cytosine / C ·hydrogen / H bonds joining basesContributions from Scientists: ·X-ray (crystallography) being used ·to show helical structure ·to show diameter of molecule ·how base pairs are arranged was shown ·how strands are arranged was shown ·modelling ·reference to using other people's ideas

1 – 2 marks  a limited description that includes either: at least three DNA features OR one contribution  the answer communicates ideas using simple language and uses limited scientific terminology  spelling, punctuation and grammar are used with limited accuracy 3 – 4 marks  a simple description that includes at least three features of DNA and at least one contribution OR two features of DNA and two contributions.  the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately  spelling, punctuation and grammar are used with some accuracy 5 – 6 marks  a detailed description of the structure of DNA that includes at least three features and two contributions.  the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately  spelling, punctuation and grammar are used with few errors

So what is the point of DNA? To make proteins. There are two main stages you need to know about – Transcription – Translation You are not usually asked for detail about each stage, but you could be asked to compare and contrast the stages, and you may be asked questions about the molecules involved so you must know about mRNA and tRNA.

Transcription and translation f8AfEvsCQ f8AfEvsCQ

Now lets have a look at an exam questions about this