Sickle Cell Anemia

Ms. Liu

Biology

5/11/12

Textbook p. 458

• You will be working on steps #1-3.

• Work with a partner to answer the questions in your notebook.

• These will serve as your notes for your poster.

Sickle cell anemia = genetic diseaseCaused by genotype: HbSHbS

Crescent

shaped

Red Blood

Cell (RBC)

Hemoglobin

• A protein in blood that…

–Gives blood it’s red color

–Carries oxygen to all the organs

In sickle cell anemia…

• The hemoglobin inside the red blood cell (RBC), clumps under low oxygen conditions.

• This causes the RBC to lose it’s flexibility and change its shape.

Readings/Qs

• Step #1: Need to Know Box p. 459

• Step #2: Incomplete Dominance p.510

• Step #3: Answer questions a-d

Step 3

A) What medical symptoms might a person with sickle cell disease experience?

Answer: Sickle cell disease can cause extreme pain and organ damage

Why?

Step 3

B) What problem in the red blood cells causes these symptoms to happen?

Answer: The red blood cells are sickle shaped (like a crescent moon)

Why?

Step 3

C) What problem in the hemoglobin molecules is associated with these changes in an individual’s red blood cells?

Answer:

• When the concentration of oxygen is low, the abnormal hemoglobin protein molecules clump together,

• This causes the red blood cells to change their shape, preventing blood flow

Step 3

D) Thinking back to your knowledge of the DNA structure…

What might be the molecular basis for phenotype of sickle cell anemia?

Answer:

• Since phenotype is determined by the genotype…

• An error in the base pairing in the DNA structure of the gene can cause the disease

p. 460

• Work on questions #4-5

• Begin posters

FACTSDNA is the genetic material of all cellular

organisms that make us who we are.

But having DNA does not explain how DNA becomes a trait such as brown eyes.

***That DNA info needs to be translated and transcribed into a cell to create a gene.

DNA is USELESS…

Unless…–There are “helpers” that can

translate DNA (make a complimentary copy) and send it out to be expressed as a phenotype.

–But 1st:

DNA RNA protein gene

RNA = ribonucleic acid• Long polymer chain like DNA but single

stranded

• Has 4 subunits/bases:

– A, C, G, and U (uracil). NO thymine (T)

• 3 types of RNA:

– mRNA (send message)

– rRNA (ribosomal makes amino acids)

– tRNA (transfers info to make protein)

RNA

• DNA is read by

a complimentary molecule

called RNA

• RNA is what translates

info from DNA to express

genes/traits

http://www.microbe.net/wp-content/uploads/2011/05/transcription.jpg

Translating DNA RNA info

• DNA: A T C A G G A C

• RNA: U A G U C C U G =brown hair

1. Write the complimentary base (opposite base)

2. Replace T with U

Posters p. 460

• Do questions #4-5

• Refer to p. 459 and 510 for readings

• Focus on poster topics #1, 5-8

What is the mRNA strand copied from this DNA strad?

DNA:

GGC TAT CTG CGC TAT ACG CTA

CCG AUA GAC GCG AUA UGC GAU

RNA:

p. 460-461

• Work on Part C: Changing mRNA protein

• Reading: p. 510, 524 and 527

Amino acids are building blocks that make up polypeptides

Polypeptides are long chains that make up protein