1. 1장 분자생물학사 완두콩의 꽃. 꽃의 색깔은 멘델이 완두콩의 유전에 관한 실험을 연구하는 데
사용한 형질 중 하나다. Shape‘n’colour/Alamy, RF.

2. A Brief History What is molecular biology?
The attempt to understand biological phenomena in molecular terms
The study of gene structure and function at the molecular level
Molecular biology is a melding of aspects of genetics and biochemistry: DNA, RNA

3. Cell:animal,plant,microorganism,virus
Cell Biology
(세포생물학)
: organelle, transport, histology
Biochemistry
(생화학)
: Nucleic acids, protein, carbohydrates, lipids
Molecular Biology (분자생물학)
: DNA, RNA
Understanding of cellular phenomena !!

4. 1.1 Transmission Genetics
Transmission genetics deals with the transmission of traits from parental organisms to their offspring
The chemical composition of genes was not known until 1944
Gene (유전자) - genetic units
Phenotype (표현형)- observable characteristics
Genotype (유전형)- genetic trait

5. Mendel’s Laws of Inheritance
A gene can exist in different forms called alleles (대립유전자)
One allele can be dominant (우성) over the other, recessive (열성), allele
The first filial generation (F1) contains offspring of the original parents
If each parent carries two copies of a gene, the parents are diploid (이배체) for that gene

6. Mendel’s Laws of Inheritance
Homozygotes (동형접합자) have two copies of the same allele
Heterozygotes (이형접합자) have one copy of each allele
Parents in 1st mating are homozygotes, having 2 copies of one allele
Sex cells, or gametes (배우자), are haploid (반수체), containing only 1 copy of each gene
Heterozygotes produce gametes having either allele
Homozygotes produce gametes having only one allele

7. Summary Genes can exist in several different forms or alleles
One allele can be dominant over the other, so heterozygotes having two different alleles of one gene will generally exhibit the characteristic dictated by the dominant allele
The recessive allele is not lost; it can still exert its influence when paired with another recessive allele in a homozygote

8. The Chromosome Theory of Inheritance
Chromosomes (염색체) are discrete physical entities that carry genes
Thomas Hunt Morgan used the fruit fly, Drosophila melanogaster, to study genetics
Autosomes (상염색체) occur in pairs in a given individual (not the X or the Y chromosome)
Sex chromosomes (성염색체) are identified as X and Y
Females have two X chromosomes
Males have one X and one Y chromosome

9. Location of Genes on a Chromosome
Every gene has its place, or locus (유전자자리), on a chromosome
Genotype is the combination of alleles found in an organism
Phenotype is the visible expression of the genotype
Wild-type (야생형) phenotype is the most common or generally accepted standard
Mutant (돌연변이체) alleles are usually recessive

10. Genetic Recombination and Mapping
In early experiments genes on separate chromosomes behaved independently
Genes on the same chromosome behaved as if they were linked
This genetic linkage (유전적연관성) is not absolute
Offspring show new combinations of alleles not seen in the parents when recombination (재조합) occurs

11. Recombination
During meiosis (감수분열), gamete formation, crossing over can occur resulting in the exchange of genes between the two homologous chromosomes
The result of the crossing-over (교차) event produces a new combination of alleles
This process is called recombination

12. Genetic Mapping
Morgan proposed that the farther apart two genes are on a chromosome, the more likely they are to recombine
If two loci recombine with a frequency of 1%, they are said to be separated by a map distance of one centimorgan (named for Morgan)
This mapping observation applies both to prokaryotes and to eukaryotes

13. 1.2 Molecular Genetics
The Discovery of DNA: The general structure of nucleic acids was discovered by the end of the 19th century
Long polymers or chains of nucleotides
Nucleotides are linked by sugars through phosphate groups
Composition of Genes: DNA? RNA? Protein? In 1944, Avery and his colleagues demonstrated that genes are composed of DNA!!

14. The Relationship between Genes and Proteins
Experiments have shown that a defective gene gives a defective or absent enzyme
This lead to the proposal that one gene is responsible for making one enzyme (효소)
Proposal not quite correct for 3 reasons:
One enzyme may be composed of several polypeptides, each gene codes for only one polypeptide
Many genes code for non-enzyme proteins
End products of some genes are not polypeptides (i.e. tRNA, rRNA)

15. Activities of Genes Genes perform three major roles
Replicated faithfully
Direct the production of RNAs and proteins
Accumulate mutations thereby allowing for evolution

16. Replication
Franklin and Wilkins produced x-ray diffraction data on DNA, Watson and Crick proposed that DNA is double helix
Two DNA strands wound around each other
Strands are complementary (상보적)– if you know the sequence of one strand, you automatically know the sequence of the other strand
Semiconservative replication (반보존적 복제) keeps one strand of the parental double helix conserved in each of the daughter double helices

17. Genes Direct the Production of Polypeptides
Gene expression (유전자복제) is the process by which a gene product is made
Two steps are required
1. Transcription (전사): DNA is transcribed into RNA
2. Translation (번역): the mRNA is read or translated to assemble a protein
Codon (유전암호): a sequence of 3 nucleic acid bases that code for one amino acid within the mRNA

18. Genes Accumulate Mutations
Genes change in several ways
Change one base to another
Deletions of one base up to a large segment
Insertions of one base up to a large segment
The more drastic the change, the more likely it is that the gene or genes involved will be totally inactivated

19. 1.3 The Three Domains of Life
Current research theories support the division of living organisms into three domains
Bacteria
Eukaryota
Archaea
Like bacteria as they are organisms without nuclei
More similar to eukaryotes in the context of their molecular biology

20. Archaea Archaea live in the most inhospitable regions of the earth
Thermophiles tolerate extremely high temperatures
Halophiles tolerate very high salt concentrations
Methanogens produce methane as a by-product of metabolism