Unraveling the DNA Mysteries: Structure, Genes & Chromosomes

1. All about your DNA

2. Structure of DNA • Every DNA molecule is made in a twisted ladder shape called a “double helix”. • The sides of the ladder are called the backbone of the DNA molecule. • The backbone is made up of alternating sugar (ribose) and phosphate molecules.

3. The rungs or steps of the DNA ladder are made up of “nitrogen base pairs” • Each rung is actually 2 individual molecules connected in the middle. • There are 4 possible nitrogen base molecules that make the rungs of the ladder: • Thymine • Adenine • Cytosine • Guanine

4. Thymine ALWAYS and ONLY bonds with Adenine. • Cytosine ALWAYS and ONLY bonds with Guanine.

5. Nucleotides • Nucleotides link together and form DNA. • Nucleotide = One ribose (sugar), one Phosphate, and one nitrogen base.

6. The DNA Hand Trick • Palm = Sugar (Ribose) • Thumb = (Phosphate) • Fingers = Nitrogen Bases (A,T,C,G)

7. Genes • 90% of your DNA is never used for anything that we know of. • “Genes” are sections of the DNA code that are actually used by the cell to create proteins. • Genes can be anywhere from 100’s to 1000’s of base pairs long.

8. Chromosomes • “Chromo” = DNA • “Some” = Body • Chromosomes are coils of DNA that are wound super tight and are X-shaped. • Every human has 23 pairs of chromosomes- 46 in total. 23 from mom, 23 from dad.

10. Boys vs. Girls • The only genetic difference between males and females occurs on the 23rd chromosome pair. • In boys, the 23rd pair do not match. One chromosome- the “Y” chromosome- is much shorter than the other. This “XY” combination makes the person male. • Females do not have the “Y”- they have two “regular” shaped chromosomes (XX). Girl Boy

11. Making Boys and Girls • Women have XX, so they can only give an X to their offspring. • Men have XY. They have an equal chance of giving either an X or Y to their child. • If a male gives an X, that would create XX (girl) when combined with the mother’s X. If the male donates Y, that means XY (boy).

14. Chromosome’s Jobs • Chromosomes are giant clumps of DNA, so they carry the critical instructions for life. • Genes are located on chromosomes. • Chromosomes are the way information is passed from one generation to the next. • Chromosomes are found in pairs- one from mom, one from dad.

15. Other Organism Chromosome Totals Fruit Fly: 8 Chromosomes

16. Pea Plant: 14 Chromosomes Kangaroo: 12 Chromosomes

17. Algae: 148 Chromosomes Dog: 78 Chromosomes

18. 1260 Chromosomes (Highest for Plants)

19. Wooly Mammoth (extinct): 58 Chromosomes • Retrieved from frozen remains

20. Protein Synthesis • Protein Synthesis = creating a protein by reading DNA code • This is how DNA code comes to life.

21. Unzipping?! • The bonds in the middle of the “steps” of the double helix can come apart. • This is called “unzipping” and must happen for the DNA code to be read.

22. Step 1 • The DNA never leaves the nucleus. Why? • The DNA is very safe in the nucleus. Even very small changes in the DNA molecule can be catastrophic. • Step 1: DNA “unwinds” and “unzips” itself at a specific gene.

23. Step 2 • A molecule called “RNA Polymerase” attaches to the unzipped DNA and reads the A, T, G, C code.

24. Step 3 • “Transcription- mRNA is created- a copy of the DNA code that replaces Thymine with Uracilto and can leave the nucleus.

25. RNA is a single strand that looks like a single twisted ribbon (a single; helix). • RNA, for some reason, does not use Thymine. • Every place Thymine would be used, RNA uses a similar molecule called “Uracil” instead.

26. Step 4 • mRNA Travels out of the nucleus and hooks onto a ribosome.

27. Step 5 • Translation- The Ribosome reads the RNA and creates the protein.

28. Step 6 • Amino acids are added to the Protein and is used by the cell for a body process or to create a new structure.

29. Protein Synthesis Flow Chart p. 28 On your paper, write the title and explain how the cell reads the DNA to make protein. DNA “unwinds” and “unzips” itself at a specific gene RNA attaches to the “unzipped” DNA mRNA makes a transcription of the DNA code replacing Thymine with Uracil mRNA travels out of the nucleus and hooks onto a Ribosome tRNA takes the mRNA to the ribosome. The Ribosome reads the RNA code through translation and creates a protein Amino Acids are added to the protein. The protein is used by the cell for a body process

30. Protein Synthesis p. 28

32. Determining Sex • The gender of a person is determined by the passing down of the “sex chromosomes” from parents to offspring. • Since females have two X’s, they can ONLY pass down an X to their offspring. • Males have an X and Y chromosome, so they can pass either X or Y to their offspring.

33. Sex-Linked Traits • The X and Y chromosomes have genes on them, just like all the other chromosomes. • The traits controlled by genes on these X or Y sex chromosomes are called sex-linked. • Some diseases are sex linked, such as hemophilia. • Ex: All the physical and chemical differences that make someone a male are sex-linked traits because they are passed down on the Y chromosome. . • hemophilacs

34. Mutations • Any abnormal change in an organisms’ DNA. Examples • If the nitrogen bases aren’t kept exactly the same, large problems or changes occur. • If a letter simply disappears, this mutation is called a “deletion”. This is very bad. • If one letter accidentally switches to a different letter, it is called “substitution”. • If extra letters are added to the code, it is called an “addition” mutation. • All mutations on active genes can cause changes/problems in the organism. i.e.. Blue eye mutation, 6 fingers, 3 nipples, etc.