EMBRYOLOGY
Cell cycle: sequence of cell growth and division. It is the
period from beginning of one division to beginning of
other. “the time it takes to complete one cell cycle is
GENERATION TIME. Chromosome become duplicated
during interphase. Cells are very active in this phase ,
synthesizing biological molecules and growing the
G1(gap) phase. Phases of Interphase
-G1 Phase = Gap 1 / Growth 1 = "Cell growth phase". Cell
increases in size. Makes proteins and organelles. Does
normal cell functions.
Think: Cell is eating and getting ready.
- S Phase = Synthesis Phase= "DNA copying phase".DNA
is duplicated. So each chromosome now has 2 copies
called chromatids. Think: Cell is making a photocopy of
its DNA. Result: Chromosome number is still 46, but DNA
amount is doubled.
,- G2 Phase = Gap 2 / Growth 2 = "Final preparation
phase". Cell checks if DNA copying was correct. Makes
more proteins and energy for cell division. Prepares
machinery for mitosis/meiosis. Think: Cell is doing last-
minute revision before exam.
COMMON TERMS:
- Interphase = The "preparation phase" of the cell.
Cell grows, copies its DNA, and makes energy before
dividing. Includes: G1 + S + G2 phases. Note: No cell
division happens here.
- Mitosis = Cell division for growth and repair. 1 cell → 2
identical cells. Chromosome number stays the same: 46
→ 46.
- Meiosis = Cell division to make sex cells. 1 cell → 4
different cells. Chromosome number is halved: 46 → 23.
- Gamete = Sex cell. Male = Sperm | Female = Egg /
Ovum
- Zygote = The first cell of a new baby. Formed when
sperm + egg fuse.
- Embryo = From fertilization to 8 weeks of pregnancy.
,- Fetus = From 9th week to birth.
- Chromosome = A package of DNA. Humans normally
have 46 chromosomes.
- Differentiation = When cells become specialized. Ex:
Some become liver cells, some become nerve cells.
Introduction to Molecular Regulation and Signaling
General Overview
- Human genome: ∼23,000 genes.
- Proteins: ∼100,000. One gene can make multiple
proteins.
- Molecular biology helped understand normal/abnormal
development + gene regulation.
GENE TRANSCRIPTION & CHROMATIN
- Chromatin = DNA + proteins, mostly histones.
- Nucleosome = Basic unit of chromatin. - 1 octamer of
histone proteins + ∼140 base pairs of DNA. -
Nucleosomes joined by linker DNA + other histone
proteins.
, - Heterochromatin = Tightly coiled DNA. Transcriptionally
inactive.
- Euchromatin = Uncoiled DNA. Active for transcription.
STRUCTURE OF A GENE
- Exons = Coding regions, translated into protein.
- Introns = Non-coding regions, between exons.
- Promoter region = Binds RNA polymerase to start
transcription. Contains TATA box.
- Transcription initiation site = Where RNA synthesis
starts.
- Translation initiation codon = First amino acid of
protein.
- Translation termination codon = Stop signal.
- 3' untranslated region = Has poly A tail for mRNA
stability + exit from nucleus.
- Enhancer sequence = Can be far from promoter,
regulates transcription rate.
REGULATION OF GENE EXPRESSION
Cell cycle: sequence of cell growth and division. It is the
period from beginning of one division to beginning of
other. “the time it takes to complete one cell cycle is
GENERATION TIME. Chromosome become duplicated
during interphase. Cells are very active in this phase ,
synthesizing biological molecules and growing the
G1(gap) phase. Phases of Interphase
-G1 Phase = Gap 1 / Growth 1 = "Cell growth phase". Cell
increases in size. Makes proteins and organelles. Does
normal cell functions.
Think: Cell is eating and getting ready.
- S Phase = Synthesis Phase= "DNA copying phase".DNA
is duplicated. So each chromosome now has 2 copies
called chromatids. Think: Cell is making a photocopy of
its DNA. Result: Chromosome number is still 46, but DNA
amount is doubled.
,- G2 Phase = Gap 2 / Growth 2 = "Final preparation
phase". Cell checks if DNA copying was correct. Makes
more proteins and energy for cell division. Prepares
machinery for mitosis/meiosis. Think: Cell is doing last-
minute revision before exam.
COMMON TERMS:
- Interphase = The "preparation phase" of the cell.
Cell grows, copies its DNA, and makes energy before
dividing. Includes: G1 + S + G2 phases. Note: No cell
division happens here.
- Mitosis = Cell division for growth and repair. 1 cell → 2
identical cells. Chromosome number stays the same: 46
→ 46.
- Meiosis = Cell division to make sex cells. 1 cell → 4
different cells. Chromosome number is halved: 46 → 23.
- Gamete = Sex cell. Male = Sperm | Female = Egg /
Ovum
- Zygote = The first cell of a new baby. Formed when
sperm + egg fuse.
- Embryo = From fertilization to 8 weeks of pregnancy.
,- Fetus = From 9th week to birth.
- Chromosome = A package of DNA. Humans normally
have 46 chromosomes.
- Differentiation = When cells become specialized. Ex:
Some become liver cells, some become nerve cells.
Introduction to Molecular Regulation and Signaling
General Overview
- Human genome: ∼23,000 genes.
- Proteins: ∼100,000. One gene can make multiple
proteins.
- Molecular biology helped understand normal/abnormal
development + gene regulation.
GENE TRANSCRIPTION & CHROMATIN
- Chromatin = DNA + proteins, mostly histones.
- Nucleosome = Basic unit of chromatin. - 1 octamer of
histone proteins + ∼140 base pairs of DNA. -
Nucleosomes joined by linker DNA + other histone
proteins.
, - Heterochromatin = Tightly coiled DNA. Transcriptionally
inactive.
- Euchromatin = Uncoiled DNA. Active for transcription.
STRUCTURE OF A GENE
- Exons = Coding regions, translated into protein.
- Introns = Non-coding regions, between exons.
- Promoter region = Binds RNA polymerase to start
transcription. Contains TATA box.
- Transcription initiation site = Where RNA synthesis
starts.
- Translation initiation codon = First amino acid of
protein.
- Translation termination codon = Stop signal.
- 3' untranslated region = Has poly A tail for mRNA
stability + exit from nucleus.
- Enhancer sequence = Can be far from promoter,
regulates transcription rate.
REGULATION OF GENE EXPRESSION
