Download goals of the human genome project

Scientific Basis
of Genetics
Janice S. Dorman, PhD
University of Pittsburgh
School of Nursing
Lessons
Cell cycle
 Chromosomes
 DNA and RNA
 Structure of a
gene

Transcription
 Translation
 Mutations

Lesson One
Cell Cycle
Mitosis

Somatic cells divide by mitosis

Parental and 2 daughter cells are
genetically identical

Parental cells are diploid
(46 chromosomes)

2 daughter cells are diploid
(46 chromosomes)
– Involves 1 cell cycle / division
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)
The stages of meiosis in an animal cell
Recombination occurs here
The stages of meiosis in an animal cell
The stages of meiosis in an animal cell
Lesson Two
Chromosomes
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
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
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)
Lesson Three
DNA (Deoxyribonucleic
Acid) and
RNA (Ribonucleic Acid)
Components of DNA / RNA

Phosphate group

Sugar group
–
–

Deoxyribose in DNA
Ribose in RNA
Bases
–
–
Adenine, guanine, cytosine, thymine
in DNA
Adenine, guanine, cytosine, uracil in
RNA
RNA Structure

RNA is generally single stranded

Sugar-phosphate groups form the
backbone of the molecule
– Can fold and create complicated
structure
– Multiple types of RNA, each with a
different function
– Nucleotides are organized 5’ to 3’

Bases form the center of the
molecule
5’ end
3’ end
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
DNA Structure

DNA is a double helix

Sugar-phosphate groups form the backbone

Two DNA strands are anti-parallel

Bases are held together by hydrogen bonds
and are complementary
– One strand, nucleotides are organized 5’ to 3’
– Other strand, nucleotides are organized 3’ to 5’
– A is complementary to T
– C is complementary to G
3’ end
5’ end
DNA Replication
Uncoil DNA

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