Chapter Study Outline

1. The Cell: Its Role in Reproducing Life and Producing Variation

a. Two Types of Organisms

i. Prokaryote (one cell)

ii. Eukaryote (many cells)

b. Two Types of Cells

i. Somatic (body) cells

ii. Gamete (reproductive) cells

2. The DNA Molecule: The Genetic Code

a. Nuclear DNA

i. Contained within the nucleus of a cell

ii. Makes up chromosomes

iii. Complete set called genome

b. Mitochondrial DNA

i. Contained in organelles in cell’s cytoplasm

ii. Inherited from the mother

c. DNA: The Blueprint of Life

i. Chemical template for every aspect of organisms

ii. Double helix, ladderlike structure

(1) Ladder forms nucleotide

(2) Ladder base made up of 4 types

(a) Adenine, thymine, guanine, cytosine

(b) Complementary pairs (A&T, C&G)

3. The DNA Molecule: Replicating the Code

a. One function of the DNA molecule is replication.

i. Part of cell division—meiosis or mitosis

ii. DNA makes identical copies of itself.

b. Chromosome Types

i. Occur in homologous (matching) pairs

(1) One in each pair from each parent

ii. Autosomes (non-sex chromosomes)

iii. Sex chromosomes

(1) X, Y

(2) Females carry only X chromosomes, while males have one X and one Y chromosome.

(3) The father determines the sex of the offspring.

4. Mitosis: Production of Identical Somatic Cells

a. DNA replication followed by one cell division

b. Diploid cell (contains full set of chromosomes)

5. Meiosis: Production of Gametes (Sex Cells)

a. One DNA replication followed by two cell divisions

b. Gametes are haploid (half the number of chromosomes).

c. Does not result in identical cell copies

d. Errors can occur during meiosis.

i. Nondisjunction, translocation

6. Producing Proteins: The Other Function of DNA

a. Proteins are chemicals that make up tissues.

b. Also regulate functions, repair, and growth of tissues

c. Proteins are made up of amino acids.

d. Structural proteins responsible for physical characteristics

e. Regulatory proteins responsible for functions: enzymes, hormones, antibodies

f. Protein synthesis involves two steps.

i. Transcription (unzipping, template for RNA)

ii. Translation (template attaches to ribosomes)

g. DNA in protein synthesis is coding DNA.

h. Most of human DNA is noncoding.

7. Genes: Structural and Regulatory

a. Structural genes are responsible for body structures.

b. Regulatory genes turn other genes on and off.

i. Homeotic (Hox) genes

ii. Master genes

8. Polymorphims: Variations in Specific Genes

a. Each gene has a specific physical location (locus).

b. Loci are valuable to understanding genetic variation.

c. Alleles on different loci are chemically alternative versions of the same gene.

d. Some genes have one allele, while others have more.

i. Mendel’s Law of Segregation: a parent passes one allele to offspring

e. Single Nucleotide Polymorphisms (SNPs)

i. Make up variation between and within human populations

f. Genotypes and Phenotypes: Genes and Their Physical Expression

i. Chemically identical alleles are termed homozygous.

ii. Chemically different alleles are heterozygous.

(1) Dominant allele is expressed in the pair.

(2) For a recessive allele to be expressed, there must be two copies.

9. The Complexity of Genetics: Polygenic Variation and Pleiotropy

a. Much of genetics is based on the “one gene, one protein” model.

b. However, many traits are polygenic and are determined by genes at more than one locus.

c. For some traits, only some of the genetic variation can be calculated (heritability).

i. Heritability ranges from 0 (none of the variation is genetic) to 1 (all of the variation is genetic).

ii. Only heritable traits respond to natural selection.

d. Measurement of heritability is complicated by pleiotropy, or a single allele having multiple effects.

i. Most complex traits are both pleiotropic and polygenic.