1. Chapter 13: Genes & Chromosomes

2. 13.1 DNA: The Molecule of Heredity
DNA is a nucleic acid
made up of nucleotides
each nucleotide made of sugar, phosphate & base
4 possible bases
adenine, thymine
cytosine, guanine

3. Chains of Nucleotides nucleotides form 2 long chains
joined by hydrogen bonds
DNA looks like a twisted ladder (double helix)
organisms are different because their nucleotides differ in sequence

4. Replication of DNA process of copying DNA = replication
enzyme unzips the DNA
free nucleotides bond to each strand, following base pairing rules
A-T, C-G
process continues until whole molecule has been unzipped & replicated
result = two identical DNA molecules

5. DNA to Protein
the sequence of nitrogen bases along DNA strands code for proteins
order of bases will determine amino acids
mRNA goes into nucleus, copies message
mRNA takes info to ribosomes, where proteins are made

6. 13.3 Genetic Changes changes in DNA = mutations
can be beneficial or detrimental
point mutation = change in single base pair of DNA
THE DOG BIT THE CAT
THE DOG BIT THE CAR
This is a substitution
1 letter (base) changed

7. changing single base can change entire protein

8. frameshift mutation
single base added or deleted from DNA, shifting all bases
THE DOG BIT THE CAT
THE OGB ITT HEC AT
Deletions and Insertions

9. Chromosomal Mutations
occur in all living org’s, very common in plants
gametes may end up with extra genes, or be missing some genes
few chromosome mutations passed on to next generation
zygote usually dies
if zygote develops, usually sterile

10. Chromosomal Mutations
Chromosomal mutations involve changes in the number or structure of chromosomes.
These mutations can change the location of genes on chromosomes and can even change the number of copies of some genes.
There are four types of chromosomal mutations: deletion, duplication, inversion, and translocation.

11. Chromosomal Mutations
Deletion involves the loss of all or part of a chromosome.

12. Chromosomal Mutations
Duplication produces an extra copy of all or part of a chromosome.

13. Chromosomal Mutations
Inversion reverses the direction of parts of a chromosome.

14. Chromosomal Mutations
Translocation occurs when part of one chromosome breaks off and attaches to another.

15. Errors in Disjunction
nondisjunction = failure of homologous chrom’s to separate properly during meiosis
trisomy = extra chromosome
triploidy = 3 sets of chromosomes
rare in animals, beneficial in plants
monosomy = missing a chromosome

16. Examples of Nondisjunction
Klinefelter’s syndrome – male with chromosomes XXY

17. Nondisjunction Examples
Turner’s syndrome – female with chromosome X only (missing the 2nd one).
Female should be XX
Male is XY
Individual w/ turner’s syndrome is just X

18. Causes of Mutations spontaneous mutations occur randomly
mutations provide variation fundamental to evolution of species
environmental agents can  mutations
X rays, UV light, radioactive substances, chemicals

19. mutations often result in sterility, lack of normal development
mutations in gametes may  birth defects
mutations in body cells may  cancer
agents that cause cancer = carcinogens