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Study Guide

[BIOL 1001] - Midterm Exam Guide - Everything you need to know! (22 pages long)


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Study Guide
Midterm

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York
BIOL 1001
MIDTERM EXAM
STUDY GUIDE

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CHAPTER 2 PRINCIPLES OF DEVELOPMENT
2.3 Cell-Cell Signals Trigger Differential Gene Expression
The function of a cell depends on its location along four body axes
1. Time (organisms current stage of development
2. Anterior to posterior (head to tail)
3. Ventral to Dorsal (belly to back)
4. Left to right
Signals activate transcription factors to turn specific genes on/off, resulting in different cell function.
Pattern Formation: events that determine the spatial organization of an embryo
- Progressive beginning with broad location on the axes (master regulators)
o Process repeats as growth continues activating gene specifying what the cell becomes
Bicoid: regulatory transcription factor that determines location on anterior-posterior axis
- Concentration gradient is important
o High: head region
o Medium: medium
o Low: posterior region
Study: fruit flies had mutations causing disruption to normal anterior-posterior determination. Mutants
had posterior structures at both ends.
Plants master regulator is a hormone: auxin; enters cells and triggers production of transcription factors
- High concentration: top of shoot
- Low concentration: bottom of the root
Morphogenes: molecules that provide spatial info during early embryonic development by a
concentration gradient
Segment: region of an animal body containing a distinct set of structures and is repeated along its length
Segmentation genes (the fruit flies had them)
- Three classes
o Gap genes: expressed first in broad regions along the head-to-tail axis
Define general position of head, thorax, and abdominal regions
o Pair-rule genes: expressed in alternating bands.
Define edges of individual segments
o Segment polarity genes
Delineate boundaries within individual segments
Hox Genes: make proteins that physically build the animal (effector genes)
Homeosis: replacement of one structure by another.
- Occurs when cells get wrong info about where they are in the body
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Master Regulator
Anterior-Posterior gradient of embryo
Gap genes
Organize cells into groups of segments along AP
Pair-Rule genes
Organize cells into individual segments
Segment Polarity Genes
Establish AP gradient within each segment
Homeotic Genes
Trigger development of structures
Effector Genes
Change proliferation, death, movement, and
differentiation of cells
Occurs in a cascade that provides progressively detailed information about where cells are located in time
and space
2.4 Changes in Developmental Pathways Underlie Evolutionary Change
For an embryo to develop cells have to:
- Proliferate, die, move or expand, differentiate, and interact in specific ways.
- If any of these processes are disrupted, embryo is likely to die
- If any of these processes are modified slightly, the effect may be a structure with a different size,
shape or activity
o Biologists realized that the genetic changes altering these developmental processes must
be the foundation of evolutionary change
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