What does DNA stand for?

Transcription

1 DNA and RNA

2 What does DNA stand for? DNA = deoxribonucleic acid NOTE: the DNA from one cell would stretch 3 metre DNA are coiled and folded. DNA has two strands.

3 What four bases are used in DNA? The four bases are: 1) Adenine (A) 2) Thymine (T) 3) Guanine (G) 4) Cytosine (C)

4 What bases join together? Adenine joins with thymine A T Guanine joins with Cytosine G C

5 Complete the following DNA strand: G C T A T A G C

6 What shape have DNA? DNA have a double helix shape

7 Chromosomes and Genes Chromosomes contain many base pairs. Example: The longest human chromosome (number 1) contains 300 million base pairs.

8 Chromosomes and Genes A gene is a section of DNA that causes the production of protein.

9 The Genetic code Different genetic codes are used to make different proteins. There are 20 different amino acids that are used in the production of proteins. DNA codes for each amino acid by having a sequence of three consecutive bases.

10 The genetic code A sequence of three bases is called a triplet (codon)

11 Genetic codes DNA triplet CAA is the code for an amino acid valine and the code CGA is the triplet for an amino acid called alanine

12 Genetic code compared to the English language Genetic code English equivalent Base Triplet (codon) Gene Genome Letter Word Paragraph Book

13 Non coding DNA 97% of DNA in human cells do not carry any codes for protein production. Non coding DNA are known as junk DNA as it has no known function.

14 Replication of DNA Before mitosis can occur the DNA in each chromosome must produce an exact copy of itself. Single chromosome strand must become double stranded chromosome.

15 DNA replication Takes place during the interphase of a cell. The double helix unwinds. Enzyme breaks the bond between the base pairs. DNA bases are found in the cytoplasm.

16 DNA replication The incoming bases attach to the exposed bases. Each new strand is identical to original strand and to other partner strand. DNA replication animation by interact Medical - YouTube

17 Video of DNA structure DNA Structure - YouTube

18 DNA Profiling At the end of this lesson you should be able to: 1.Outline the four stages involved in DNA profiling 2.Define the process of DNA profiling 3.Give two applications of DNA profiling 4.Define genetic screening

19 DNA Profiling American researchers discovered non-coding regions of DNA Professor Alec Jeffries developed the process of DNA profiling First conviction based on DNA evidence

20 What is DNA profiling? Also known as genetic fingerprinting. It is a method of making a unique pattern of bands from the DNA of a person. This can be then used to distinguish that DNA from other DNA.

21 DNA Profile

22 Four steps in DNA profiling: 1) DNA is released 2) DNA is cut into fragments 3) The fragments are separated 4) Patterns are compared

23 1) DNA is released Cells are broken down to release their DNA

24 DNA is released

25 The section of DNA bases cut will be of different lengths because of the different distances between the base sequences. 2) DNA is cut into fragments Isolated DNA is cut into fragments using enzymes (restriction enzymes) Example: The restriction enzyme will cut the DNA at the base sequence GAATTC. The enzyme cuts the DNA between the G and the A bases

26 Restriction enzymes

27 3) Fragments are separated Sections of DNA are separated based on their size. They are separated by a process called gel electrophoresis. An electric current is applied along the gel which allows bands of small DNA fragments to be separated from bands of larger DNA fragments,

28 Fragments are separated: A radioactive material is added to combine with DNA fragments to produce a flourescent image.

29 Patterns are compared If two different DNA samples are the same, then the two samples must have come from the same person.

30 Applications of DNA profiles (DNA 1) Crime: fingerprints) Blood, hair, semen or salvia can be used for DNA profiling 2) Medical (Paternity disputes): Can be used to determine who is the parent of a child.

31 Comparing DNA profiles:

32 Comparing DNA profiles

33 Applications of DNA profiles (DNA fingerprints) 3) Genetic screening Adult screening Adults who want to know if they have a defective gene or disorder Foetal screening Cells can be removed from the placenta and can be tested for a genetic disorder

34 Ethics of genetic screening? Genetic screening may cause ethical problems. Example: employers or insurance companies may be wary of this information. Would a foetal screening encourage parent to carry out termination of pregnancy

35 Video on DNA profiling DNA Medical Screening YouTube DNA Matching - YouTube

36 RNA (ribonucleic acid) RNA also consist of four bases RNA contains the base uracil instead of thymine. What are the four bases: 1) Adenine (A) 2) Uracil (U) 3) Guanine (G) 4) Cytosine (C)

37 Facts on RNA RNA is a single stranded molecule. The bases in RNA are complementary to those in a section of DNA. Example: If DNA has sequence GGAATC along one strand, then the RNA will have the sequence CCUUAG

38 Base pairing between DNA and RNA

39 Base pairing between DNA and RNA

40 Differences between DNA and RNA DNA RNA Has the bases AT GC Has the bases AU GC Double stranded Single stranded Found in the nucleus Found in nucleus and cytoplasm

41 Detailed structure of DNA DNA is made up of units called nucleotides. A long chain of nucleotides is called a polynucleotides.

42 Detailed structure of DNA

43 Nucleotides Three parts in a nucleotides: A phosphate group A sugar Nitrogen base (Adenine, Thymine, Cytosine, Guanine)

44 Purines and Pyrimidines Purine bases = adenine (A) and guanine (G) Pyrimidine bases = thymine (T) and cytosine (C)

45 Structure of a Nucleotide Phosphate Sugar Nitrogen Base Sugar = Deoxyribose (D) Phosphate group = (P) Nitrogen base = A or G or T or T

46 What is a polynucleotide? P P P P D A P = Phosphate D = deoxyribose (sugar) D G D T D C

47 Base Pairs Hydrogen bonds

48 Base Pairs Adenine and thymine form two weak hydrogen bonds. Guanine and cytosine form three hydrogen bonds. Each base pair has a purine and pyrimidine.

49 Double Helix Crick and Watson discovered that DNA consists of two spiral chains of polynucleotides. The double helix is made of deoxyribose and a phosphate. The rungs are the base pairs on the inside.

50 Double Helix

51 Protein synthesis Genes are used to produce different proteins. The major steps involved in protein synthesis include: 1) Transcription 2) Translation

52 Types of RNA: Three types of RNA: A. messenger RNA (mrna) B. transfer RNA (trna) C. ribosomal RNA (rrna) Remember: all produced in the nucleus!

53 3) The enzyme RNA polymerase joins the RNA bases together to form mrna (messenger RNA) Steps involved in protein synthesis: 1) Enzymes start to unwind the DNA double helix in the nucleus. 2) Complimentary RNA bases join to the exposed DNA strand (transcribed)

54 Transcription Transcription is the making of mrna from DNA

55 Protein synthesis 4) Each mrna strand carries: i) a start codon ii) a series of codons of different amino acids iii) a stop codon

56 Transcription

57 Translation making a protein using the mrna code 5) mrna moves from the nucleus to the cytoplasm 6) rrna (ribosomal RNA) are found in the ribosome 7) mrna form a weak bond with the rrna in the ribosome. NOTE: ribosome is the site for protein synthesis

58 mrna found in the ribosome

59 Protein synthesis trna (transfer RNA) is found in the cytoplasm. trna contains an anticodon and a particular amino acid.

60 Protein synthesis 9) trna is attracted to the mrna in the ribosome. 10) The anticodon on the trna compliments the codon on the mrna. 11) As the trna attach to the mrna in the ribosome, it also brings with it an amino acid.

61 Translation

62 Protein Synthesis 12) As the trna continue to enter the ribosome, the amino acids detach from the trna and bond together to form a new protein. 13) trna leave the ribosome without any amino acids and pull with it the mrna strand out of the ribosome. 14) The process stops once it has reached the stop codon. A new protein has been produced.