Unit A 3.0: DNA

1. Unit A 3.0: DNA

3. I. Organization of DNA A. DNA (deoxyribonucleic acid) • A set of “blueprints” for the organism • Every cell in the body has the exact same DNA copies (except gametes – ½ the amount) *Is inherited from parents ( ½ mom + ½ dad) and creates variation*

5. Organization of DNA A. DNA • Double helix shape (spiral ladder) which was found by Watson and Crick • Each ladder rung is made from 4 bases: • Adenine (A) • Guanine (G) • Thiamine (T) • Cytosine (C • The order that the bases are arranged is called our genetic code

6. A always binds with T G always binds with C

7. Organization of DNA B. Genes • A small section of the DNA spiral • Each gene creates a protein which produces our traits Ex. Eye color Pigment gene – have pigment (green or brown) or not (blue eyes) • Genes are arranged in pairs; each gene is on a different chromosome • There are two genes for eye color

10. Organization of DNA B. Genes • One gene is given by the mother; the other given by the father • Alleles are variations of the gene • Ex. Alleles of eye color are brown, blue, green • Draw!

13. Organization of DNA C. Chromosomes • The packages of compressed DNA • There are 2 copies of each chromosome in a body cell. • Human body cells = 46 chromosomes (2 copies) • Human gametes = 23 chromosomes (1 copy)

14. I. Organization of DNA • Predict how many chromosomes a dog has: • How many a cat has? • Is it linked to how dominant the species is?

16. I. Organization of DNA • Males have 1 X and 1 Y chromosome • Females have 2 X chromosomes

18. Ex. How are the terms genes, chromosomes and DNA related? Draw a picture to illustrate.

19. II. Cell Division • Two reasons cells divide are to: • Grow • Create cells for reproduction Two types of cell division are: • Mitosis • Meiosis

20. II. Cell Division A. Mitosis(hyper) -is when a cell creates 2 copies of its DNA so it can equally split into two identical cells Ex. Binary fission – a bacteria makes double its DNA then splits to create 2 bacteria, each with a full set of DNA • Used when species grow and during asexual reproduction

21. II. Cell Division B. Meiosis • Is when a cell divides to create new cells with ½ the DNA of the original cell • Used to create gametes (sperm/egg) in sexual reproduction • Four cells are created in total

23. Patterns of Inheritance • Purebred (true breeding) – those organisms with the exact same traits as their ancestors Ex. Offspring of 2 labs • Hybrids – offspring made by mating organisms with different traits Ex. Offspring of a pug with a beagle

24. Purebred Hybrid

25. Patterns of Inheritance • Allele • Genotype: the letters representing the gene of an organism • Ex. TT or tt or Tt • Phenotype – the appearance of an organism because of its genes • Ex. TT – black fur • tt – white fur

26. Patterns of Inheritance A. Dominance • Dominant Trait- the variation of a trait which requires only 1 copy to appear • Represented by capital letters • Recessive Trait – the variation of a trait which requires 2 copies to appear • Represented by lowercase letters *Remember : A combination of 2 genes creates a trait*

27. Patterns of Inheritance • Punnett Squares • A tool used to study the outcome of crossing two sets of genes • One parent’s genes go along top; one along left side See handout worksheet

28. Ex. 1: Purebred black cat x Purebred white cat • Genotypes of the black parent: White parent: • What are the phenotypes of the offspring? • What are the genotypes of the offspring? • How many offspring are: • A) Black b) White • c) Purebred d) Hybrids

29. Ex. 2: Black hybrid x White purebred cat

30. Patterns of Inheritance B. Incomplete Dominance • When neither allele is dominant; they trait is a mixture of each allele Ex. White snapdragon x Red snapdragon

31. Patterns of Inheritance • Some traits are controlled by more than 1 gene • Ex. Eye color, hair color, skin color • Some traits are effected by the environment • Thalidomide babies