1. Scientific Basis of Genetics
Janice S. Dorman, PhD
University of Pittsburgh
School of Nursing

2. Lessons Cell cycle Transcription Chromosomes Translation DNA and RNA
Structure of a gene
Transcription
Translation
Mutations

3. Lesson One
Cell Cycle

4. The eukaryotic cell cycle
The eukaryotic cell cycle. Cells that are destined to divide progress through a series of stages, denoted G1, S, G2, and M phases (mitosis). This diagram shows the progression of a cell through mitosis to produce two daughter cells. The original diploid cell had two pairs of chromosomes, for a total of four individual chromosomes. During S phase, these have replicated to yield eight sister chromatids. After mitosis is complete, there are two daughter cells each containing four chromosomes.

5. Mitosis Somatic cells divide by mitosis
Involves 1 cell cycle / division
Parental and 2 daughter cells are genetically identical
Parental cells are diploid (46 chromosomes)
2 daughter cells are diploid (46 chromosomes)

6. Meiosis Germ cell precursors (parental cells) divide by meiosis
Involves 2 cell cycles / divisions instead of 1
Germ cells precursors and 4 gametes (daughter cells – either egg or sperm) are NOT genetically identical
Germ cell precursors are diploid (46 chromosomes)
4 gametes are haploid (23 chromosomes)

7. The stages of meiosis in an animal cell

8. The stages of meiosis in an animal cell
Recombination occurs here
The stages of meiosis in an animal cell

9. The stages of meiosis in an animal cell

10. Lesson Two
Chromosomes

11. Chromosome Structure
Chromosomes have 2 arms that are separated by the centromere:
p arm – for petite
q arm – long arm
Ends of chromosomes are called telomeres

13. The steps in eukaryotic chromosomal compaction leading to the metaphase chromosome. The DNA double helix is wound around histone proteins and then further compacted to form a highly condensed metaphase chromosome

14. Chromosome Types Autosomes: the numbered chromosomes
All individuals have 2 copies of each type of autosome (homologous chromosomes – 1 maternal, 1 paternal)
Sex chromosomes: the X and Y chromosomes
All individuals have 2 sex chromosomes
XX = female
XY = male

15. Karyotype An organized picture of the chromosomes found in a cell
Captured during mitosis, just before cell divides
Generally demonstrates the normal complement of chromosomes
46,XX for females and 46,XY for males
Can point out gross chromosomal abnormalities (such as extra or missing chromosomes)

19. DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid)
Lesson Three
DNA (Deoxyribonucleic Acid) and
RNA (Ribonucleic Acid)

20. Components of DNA / RNA Phosphate group Sugar group Bases
Deoxyribose in DNA
Ribose in RNA
Bases
Adenine, guanine, cytosine, thymine in DNA
Adenine, guanine, cytosine, uracil in RNA

21. The components of nucleotides
The components of nucleotides. The three building blocks of a nucleotide are one or more phosphate groups, a sugar, and a base. The bases are categorized as purines (adenine and guanine) and pyrimidines (thymine, uracil, and cytosine).

22. The structure of nucleotides found in (a) DNA and (b) RNA
The structure of nucleotides found in (a) DNA and (b) RNA. DNA contains deoxyribose as its sugar, and the bases A, T, G, and C. RNA contains ribose as its sugar, and the bases A, U, G, and C.

23. RNA Structure RNA is generally single stranded
Can fold and create complicated structure
Multiple types of RNA, each with a different function
Sugar-phosphate groups form the backbone of the molecule
Nucleotides are organized 5’ to 3’
Bases form the center of the molecule

24. 5’ end
A strand of RNA. This structure is very similar to a DNA strand, except that the sugar is ribose instead of deoxyribose and uracil is substituted for thymine
3’ end

25. Double stranded RNA: Possible secondary structures of RNA molecules
Double stranded RNA: Possible secondary structures of RNA molecules. The double-stranded regions are depicted by connecting hydrogen bonds. Loops are noncomplementary regions that are not hydrogen bonded with complementary bases. Double-stranded RNA structures can form within a single RNA molecule or between two separate RNA molecules

26. DNA Structure DNA is a double helix
Sugar-phosphate groups form the backbone
Two DNA strands are anti-parallel
One strand, nucleotides are organized 5’ to 3’
Other strand, nucleotides are organized 3’ to 5’
Bases are held together by hydrogen bonds and are complementary
A is complementary to T
C is complementary to G

27. A strand of DNA. This shows the phosphodiester backbone of DNA, which is a very strong bond.

28. 3’ end
5’ end

29. Key features of the structure of the double helix

30. DNA Replication Uncoil DNA  Strand Separation  
Strand Separation 
Templates are Single Stranded 
RNA Primers Needed For New Strands 
Both DNA Strands Extended From the RNA Primer (5’ to 3’)
One Strand is the Leading Strand
Other Strand is the Lagging Strand

31. Enzymology of DNA replication – note that one strand is made continuously and is called the Leading strand, while the other strand needs to be made in pieces (called Okazaki fragments) and is called the lagging strand. One strand needs to be made in pieces because the polymerase can only work by making the new strand in the 5’ to 3’ direction (only works in one direction).