GENE

EXPRESSION Individuality & Mutations

I. Are all genes turned on in all cells?

The answer is NO!

Every body cell contains your DNA (genetic

make-up)

Cells “use” only genes specific for function

EX. Red blood cells use only genes that

make it carry oxygen

Can you list more examples of

proteins made? Enzymes, insulin, cell membrane, hair, muscles

**THEREFORE, NOT ALL DNA IS

EXPRESSED (MADE INTO PROTEIN) IN EVERY CELL!**

This video segment investigates why one

species of fruit fly has wing spots while

another genetically similar one does not.

As the video explains, although two

organisms may both possess the same

gene linked to a particular trait, this trait

may not be expressed unless the gene is

turned on

4

Turning genes on video (5 min):

http://www.teachersdomain.org/reso

urce/novat10.sci.life.evo.fruitfly/

II. Review: Determining Sex Human Chromosomes

46 in a normal human cell!

Two types: a) Normal chromosomes: 44 in each BODY CELL; 22 in each

GAMETE (sex cell) b) Sex chromosomes: 2 in each BODY CELL; 1 in each

GAMETE (sex cell) MALE: X and Y FEMALE: X and X

Is this a

male or a

female??

Karyotype

Chances for having a boy or girl? 50% OF

COURSE…LET’S SEE!

X Y

X X

XX

XX XY

XY

http://www.brainpop.com/science/cellularlifeandgenetics/geneticmutatio (2:33)ns

DNA fails to copy accurately

III. Mutations: What happens when DNA goes wrong

A change in the genetic material which effect genetic information and traits

Not all mutations are bad, some are beneficial

Ultimate source of genetic variation (depends on environment)

MUTATIONS MUST OCCUR IN SEX CELLS IN ORDER FOR THEM TO BE PASSED ON TO NEXT GENERATION!!!!!!!!!!

When do mutations occur?

During replication (meiosis / mitosis) and protein synthesis

Mutations caused by Mutagenic Agents:

1. Radiation

x- rays, UV, radioactive substances

2. Chemicals

formaldehyde, benzene, asbestos fibers, nicotine

A. Chromosomal Mutations Change in number of chromosomes or structure

Ex: normal human body cell = 46 Human Karyotype Arrangement of a male

Types of Chromosomal Mutations 1. Deletion

A portion of a chromosome is taken

away form a chromosome

2. Duplication

A portion of one chromosome

breaks off and is attached to its

homologous chromosome giving it

an extra copy

3. Inversion

A portion of a chromosome breaks

off and then becomes reattached to

the same chromosome in an

inverted (upside down) fashion

4. Translocation

transfer of one section of a

chromosome

Genetic Disorders Relating to

chromosomal mutations

Down Syndrome

Due to nondisjunction

failure of homologous

chromosomes to

separate during

meiosis

An extra

chromosome 21

Klinefelter Syndrome

• XXY abnormal sexual development and infertility

B. Gene Mutations

A random change in DNA sequence

**Review** What does DNA ultimately code for?

Proteins!!!

Is construction of protein based on original DNA strand?

Yes! (b/c it is what codes for mRNA)

What would happen to the protein if DNA sequence

was changed?

Wrong protein made

Wrong shape of protein

This would make protein unusable

DNA MUTATION VIDEO

http://www.bing.com/videos/search?q=mutation+videos&FORM=VIRE6#v

iew=detail&mid=0F73B8E85CE1098084470F73B8E85CE109808447

A. POINT MUTATION: affects 1 nucelotide (base)

Example: CTC on DNA makes mRNA = GAG codes for

GLUTAMINE If T changed to A, would have GUG which codes for VALINE

Wrong AMINO ACID is coded for which means, wrong

PROTEIN is made

Types of Gene Mutations

B. FRAME-SHIFT: A base is deleted or added

Example: TCA-TTT on DNA;

mRNA = AGU-AAA on codes for Serine + Lysine

If the T is deleted in the DNA, the mRNA would now

read GUA-AA

rRNA will CODE “GUA” first which is for Valine

1. Similar if a base is added

2. Wrong AMINO ACID is coded for = wrong PROTEIN is

made OR Translation will abruptly STOP

Disorders from Gene Mutations

Sickle cell anemia – Sickle shaped

cells get caught in capillaries (can’t

transport oxygen sufficiently)

Cystic Fibrosis- affects recessive allele

mutating the CFTR gene

Normal red

blood cells (top)

and sickle cells

(bottom)

IV. Environmental Expression

Some genes are “turned on” under certain environmental conditions.

EX. Himalayan Rabbit: Fur changes color due to TEMPERATURE change WARM = White fur (no pigment

produced)

COLD = Black fur

Why does this make sense? Because black absorbs the heat,

helping little bunny rabbit to stay warm

• How do we know that traits and diseases are genetically related?

• THE HUMAN GENOME PROJECT

• What is it? Project to identify the location of 30,000 genes

• Why do it? To identify the locations of genetic diseases and possibly control and/or eliminate them

• How far along are we? The map was completed in 2004

V. The Human Genome

Class and/or Homework:

Topic 3 RB pages 50-52

Read these pages and answer questions 23-31 on loose leaf paper

Topic 3 RB pgs 50-52

23) 4

24)a gene mutation is a change in the instructions of the gene. The nitrogenous bases forms the code instructions, so changing this sequence would alter the amino acid/protein

25) 3

26) 2

27) 4

28) 1

29) 1

30) 4

31) 1