scientific basis of genetics janice s. dorman, phd university of pittsburgh school of nursing
TRANSCRIPT
Scientific Basis of Genetics
Janice S. Dorman, PhDUniversity 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
– 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)
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
The stages of meiosis in an animal cell
Recombination occurs here
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
– 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
3’ end
5’ 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– 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
3’ end 5’ end
DNA ReplicationUncoil 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 StrandOther Strand is the Lagging Strand