Zoology Midterm Study Guide

4. SEX-LINKED INHERITANCE autosomes—22 pair in people heterosomes—1 pair in people (XY sex chromosomes)
XX=female XY=male
Red-green color blindness in people:
PREVIOUSLY NOTED FROM TUESDAY SEPTEMBER 3, 2013

5. No dominance example homozygous black= black chicken homozygous white= white chicken heterozygous= gray

6. Multiple factors
Several sets of alleles on entirely different chromosomes affect the expression of a single characteristic.
Skin color in people
Stature on people
Crop yield

7. Inheritance of sex (heterosomes) female XX male XY

8. Sex influenced characteristics dominant in male recessive in female baldness in people horns in cattle
9. Linkage
Genes for different characters together on the same chromosome
Thus gene segregation and independent assortment is impossible
Crossing over can separate these genes
Chromosomal maps

Changes in genetic traits due to mutations:
1. Chromosomal mutations (altered karyotypes)
Down syndrome
Retarded mental/physical development
Extra chromosome 21 (3n) triploid
Other karyotypic mutations
Inversions translocations
Deletions duplication
2. Gene mutations (chemical changes in genes on chromosomes)
a) radiation (x-rays, ultraviolet, cosmic rays, radioactivity)
b) chemical (complex hydrocarbons in the environment)
(mutation rate is low, only one per person)
GENES—the hereditary units on chromosomes
Genes consist of DNA (deoxyribosenucleic acid) molecules having the following components:
1. Nitrogenous bases ring compounds lots of N, C, H, often O
Purines (double ring)
A—adenine (double bond)
G—guanine (triple bond)
Pyrimidines (single ring)
T—thymine (double bond)
C—cytosine (triple bond)
TA GC
2. Nitrogenous bases are attached to a ribose (pentose) sugar lacking one oxygen
3. Sugars with their bases held together in a long string by phosphate (PO4) molecules
4. Whole long ladder-like structure twisted into a double helix

A nucleotide is a unit of both a DNA and RNA molecule consisting of a nitrogenous base, its ribose sugar and phosphate molecule.
RNA (ribosenucleic acid) is transcribed by DNA contains the information for protein synthesis stored in the DNA
One more ribose oxygen than in DNA
Has uracil (U) replacing thymine (T)
Kinds of RNA: (nucleolus to cytoplasm) mRNA—messenger RNA: codon (boss) tRNA—transfer RNA: anticodon (worker) rRNA—ribosomal RNA (assembly line)

Genetic Code:
4 letter alphabet (4 nitrogenous bases) TACG
3 letter words (codons & anticodons)
20 meanings (20 amino acids) arranged in long nucleotide sentences

the big picture (how it works_
1. DNA has genetic information
2. DNA copies information to 3 RNA types
3. mRNA and other types seep through nuclear pores into the cytoplasm
4. Cytoplasm contains the amino acids held by tRNA chunks (eat> gut> blood> cells)
5. mRNA and tRNA are joined by rRNA
6. Amino acids from tRNA guided by mRNA
7. The proteins are the enzymes that catalyze metabolic processes and make us what we are

one gene-> one enzyme theory (was hypothesis now a proven fact or Law of Nature)

Genetic Engineering
One example—making bacteria produce human insulin (diabetes)
1. Cleave genes at specific base sequence locations using one of the bacterial restriction endonuclease enzymes
2. Splice insulin gene into bacterial plasmid (circle of genes outside main chromosome)
3. Reproducing bacteria now produce insulin of the human type

gene repair engineering a similar process when introducing normal non- mutated genes, and so is adding….

EVOLUTION organic evolution is the evolution of organisms and is defined: various organisms that exist today were derived from ancestral forms through progressive change in structure and function.
Greeks knew fossils were ancient dead beasts but did not make much of it
Erasmus Darwin (Darwin’s grandfather)
Lamark (French)—inheritance of acquired traits (strength, mouse tails, and inheritance)
“The Voyage of the Beagle” 1831-1836 (Brit)
Charles Darwin & Robert Fitzroy in their 20s
European museum full of worldwide specimens
Charles Darwin, Alfred Wallace 1858
Darwin followed with many books

Steps in the process of organic evolution:
1. Organisms have high biological potential (reproductive rate)
2. They reproduce rapidly enough to overcome their limited resources (food and space)
3. Environmental resistance ensues (overcrowding)
4. Struggle for existence results
5. Genetic variation exists in species thus providing inherited traits
6. Natural selection favors the best traits
7. Survival of the fittest having the most advantageous traits (fitness is leaving the most genes)