Alejandro Morales

Ms. McFarlane

Biology HL

7th September, 2014

Pg. 81

4.1.1 State that eukaryotic chromosomes are made of DNA and protein

Eukaryotic chromosomes consist of DNA wrapped around histone proteinsThis forms the basic structure of the nucleosome, which is packed together to form chromatin (in a 'beads on a string' arrangement)Chromatin will supercoil and condense during prophase to form chromosomes that can be visualised under a light microscope

4.1.2 Define gene, allele and genome

Gene: A heritable factor that controls a specific characteristic, consisting of a length of DNA occupying a particular position on a chromosome (locus)Allele: One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same locus as other alleles of the geneGenome: The whole of the genetic information of an organism

4.1.3 Define gene mutation

Gene mutation: A change in the nucleotide sequence of a section of DNA coding for a particular feature

4.1.4 Explain the consequence of a base substitution mutation in relation to the process of transcription and translation using the example of sickle cell anaemia

A base substitution mutation is the change of a single base in a sequence of DNA, resulting in a change to a single mRNA codon during transcriptionIn the case of sickle cell anaemia, the 6th codon for the beta chain of haemoglobin is changed from GAG to GTG (on the non-coding strand)This causes a change in the mRNA codon (GAG to GUG), resulting in a single amino acid change of glutamic acid to valine (Glu to Val)

DNA: GAG to GTG (non-coding strand)mRNA: GAG to GUGAmino Acid: Glu to Val The amino acid change alters the structure of haemoglobin, causing it to form fibrous, insoluble strandsThis causes the red blood cell to adopt a sickle shape

Consequences of Sickle Cell Anaemia

The insoluble haemoglobin cannot effectively carry oxygen, causing individual to feel constantly tiredThe sickle cells may accumulate in the capillaries and form clots, blocking blood supply to vital organs and causing a myriad of health problemsAlso causes anaemia (low RBC count), as the sickle cells are destroyed more rapidly than normal red blood cellsSickle cell anaemia occurs in individuals who have two copies of the codominant 'sickle cell' allele (i.e. homozygotes)Heterozygous individuals have increased resistance to malaria due to the presence of a single 'sickle cell' allele (heterozygous advantage)

Pg. 84

1.

Locus

2. A gene is a sequence of DNA that controls a specific feature such as eye colour.An allele is a variation of a gene such as blue eyes, brown eyes and green eyes.

3. Eukaryotic 23 pairs of chromosomes. DNA is associated with proteins which help to keep the DNA organised. Prokaryotic only one chromosome, and the DNA is not associated with proteins.

4. Because there is genetic material from each parent, and each sex cell has 23, hence they must exist in pairs.

5. It is reduction division, because the number of chromosomes has been reduced.

6. Because in meiosis, the result is four haploid daughter cells, and mitosis is two diploid daughter cells, hence meiosis is needed to create cells that one day will have to fuse together and create the full set of chromosomes in the fertilised zygote.

7. Sex cells gametes

8.

9. Because if a women is aged over 35, then it is recommended that she should get a karyotype preoccupation about the chromosomal integrity of the unborn.

10.

Did I read the section from the textbook over the topic that we will be discussing in class, and make note of any key words or concepts? *

Sort of, I read the questions and then skimmed the chapter for the answers to the questions.

Did I define the key words from this unit? *

No.

Did I answer all of the questions that I understood fully, paying attention to the command terms.*

Yes, I answered the questions that I understood. When I didn't know an answer, I looked back over the text. If I still didn't understand a question, I made note of it to remind myself to ask about this in class during the discussion.

Muddy points and Challenges

Below write down any challenges you had completing the assignment, and identify any muddy points that you would like for me to focus on during class

How supercoiling works and why it happens, Id like to understand that better. Also maybe protein coded genes and highly repetitive sequences.

(DIDNT UNDERSTAND QUESTION 3B)