Semester 2, Day 8

Cell Specialization and Gene Expression

Agenda Review Central Dogma Turn in HW (Packets 11.4-11.5) Quiz on Central Dogma Lecture on Cell Specialization and Mutations Reading/Work Time

Review What is the definition and diagram of the central dogma? What are the roles of DNA, RNA and protein in the central

dogma? What is the first “step” of the central dogma? Know the steps! What is the second “step” of the central dogma? Know the

steps! What is a codon? Be able to use scientific language! Which amino acid do all proteins begin with? (Hint: look at

the genetic code chart) If given a strand of DNA, can you determine what the mRNA

strand should be? (Hint: don’t use T, use U!) With that mRNA strand, be able to use the genetic code chart

to determine the chain of amino acids. (Remember: which amino acid comes first???)

Homework Due Annotate the packet Sections 11.4-11.5

Do all concept checks Chapter 11 Review

#3-6, 12, 14, 15, 19, 20, 22-24

Cell Specialization & Gene Expression We have 100 trillion cells, but they don’t all

look the same (200 types):

Neuron CellEpithelial (Skin) Cells

Red Blood Cells

Muscle CellSperm Cell

Cell Specialization & Gene Expression All of these cells contain the same exact copy of DNA (except sperm), BUT:

Image Source: questgarden.com

Same DNA, but only

some genes are

expressed

Definitions

**Gene: a portion of DNA that codes for a

protein

**Gene Expression: the proteins formed by

the decoding of specific genes in a cell

Cell Specialization & Gene Expression Zygote: first cell of an organism

Day 0

Image Source: www.bbc.co.uk Image Source: commons.wikimedia.org

Morula (16-64 cells)

All of these cells are TOTIPOTENT: capable of differentiating (specializing) into any and all types of cells

Cell Specialization& Gene Expression

Blastocyst (70-100 cells)

Embryoblast cells are PLURIPOTENT: capable of

differentiating into the cells of one of three groups.

Image Source: www.boundless.com Image Source: www.scq.ubc.ca

**Stem cell therapy can

use embryoblast

cells!

Mutations & Gene Expression Mutation: A change in a DNA sequence. May

or may not affect gene expression (the protein). Point Mutation

1. T H E / F A T / C A T / A T E / T H E / R A TT H E / F A T / K A T / A T E / T H E / R A T

2. T H E / F A T / C A T / A T E / T H E / R A TT H E / F A T / B A T / A T E / T H E / R A T

“Silent Mutation”

Not Silent

Message still sounds the

same

Message sounds

different

Mutations & Gene Expression

Image Source: waynesword.palomar.edu

Recall: 64 codons, only 20

amino acids.

Mutations & Gene Expression Point Mutations (cont.)

Normal:

Point (Silent):

Point (not silent):

DNA Template Strand T A C G T G C G A A C C T G A A T T

mRNA Strand A U G C A C G C U U G G A C U U A AProtein Methionin

e Histidine Alanine Tryptophan Threonine STOP

DNA Template Strand T A C G T G C G C A C C T G A A T T

mRNA Strand A U G C A C G C G U G G A C U U A AProtein Methionin

e Histidine Alanine Tryptophan Threonine STOPRecall: 64 codons, only 20 amino acids; helps prevent protein changes!

DNA Template Strand T A C G T G C G A A C G T G A A T T

mRNA Strand A U G C A C G C U U G C A C U U A AProtein Methionin

e Histidine Alanine Cysteine Threonine STOPJust one amino acid change can change an entire protein!

Mutations & Gene Expression

Mutations

Point

Silent (doesn’t

affect gene expression)

Not Silent (affects

gene expression)

?

? ?

Mutations

Point

Silent Not Silent

Frameshift

Insertion Deletion

Mutations & Gene Expression

Mutations & Gene Expression Frameshift Mutations: insertion or deletion of

nucleotide(s) results in the reading of codons to shift.1. T H E / F A T / C A T / A T E / T H E / R A T

T H E / F A E / T C A / T A T / E T H / E R A / T

2. T H E / F A T / C A T / A T E / T H E / R A TT H E / A T C / A T A / T E T / H E R / A T

InsertionLetters after insertion are shifted to the right

All Nonsense = Message Destroyed

Deletion

All Nonsense = Message Destroyed

Letters after insertion are shifted to the left

Mutations & Gene Expression Frameshift Mutations (cont.)

Normal:

Frameshift Insertion:

Frameshift Deletion:

DNA Template Strand T A C G T G C G A A C C T G A A T T

mRNA Strand A U G C A C G C U U G G A C U U A AProtein Methionin

e Histidine Alanine Tryptophan Threonine STOP

DNA Template Strand T A C A G T G C G C A C C T G A A T T

mRNA Strand A U G U C A C G C G U G G A C U U A AProtein Methioni

ne Serine Arginine Leucine Aspartate Leucine

DNA Template Strand T A C T G C G A A C G T G A A T T

mRNA Strand A U G A C G C U U G C A C U U A AProtein Methionin

eThreonin

e Leucine Glycine Leucine

No Stop

Completely Different!

Completely Different!

Mutations & Gene Expression Which is more destructive? Point OR

FrameshiftChanges MANY amino acids

Mutations

Point

Silent Not Silent

Frameshift

Insertion Deletion

Can be a “silent mutation” or only

changes one amino acid

Reading/Work Time Section 11.3

Cornell Notes #1-6

Chapter 11 Assessment #2, 4, 12, 13, 14, 25