4.1.1- 4.1.4 | Chromosomes, genes, alleles and mutations

Rania and Bryan

4.1.1

• Eukaryotic chromosomes consist of a DNA-protein complex that is organized in a compact way which permits the large amount of DNA to be stored in the nucleus.

Eukaryote chromosomes are made up of DNA and proteins…

4.1.2 • A gene is a heritable factor that controls a specific characteristic.

• Alleles are one specific form of a gene. They differ from other alleles by one or a few bases only and occupy the same gene locus as other alleles of the gene.

• Genomes are the whole genetic information of an organism. • Eukaryote genomes

are contained in a single, haploid* set of chromosomes.

The human genome is made up of about 35000 genes.

* Haploid - the number of chromosomes in a gamete of an organism.

Gene Mutations 4.1.3

•Gene mutations are a change to the base sequence of a gene.

Mutations range in size from a single DNA base to a large segment of a chromosome.

Gene mutations occur in two ways: they can be inherited by a parent or developed during a person’s lifetime.

• Mutations also occur in an egg or sperm cell, or those occurring right after fertilization (de novo mutations).

Note: These types of mutations can explain genetic disorders in which the child may have this mutation in every cell, but there is no history of this disorder in the family.

• Acquired (somatic) mutations occur in the DNA of individual cells during a person’s lifetime.

these changes can be caused by environmental factors such as ultraviolet radiation from the sun, or when a mistake is made in the replication during cell division.

Note: These types of mutations cannot be passed on to the next generation.

4.2.1 – 4.2.2 | Mutations and Meiosis

Sickle Cell Anemia

• Sickle Cell Anemia is a good example of a mutation.

• In sickle cell anemia the switch of just one nucleotide causes glutamic acid to be replaced by valine, which causes red blood cells to become stiff and stick to each other forming long fibers that obstruct blood flow to other parts of the body.

4.1.4

• The switch occurs when the base code CAG mutates to CTG. That one small change is enough to cause the disease.

•During Transcription there is a mistake in the code and that causes for the codon to be misread, switching the amino acid that normally pairs with the base code causing the sickle cell anemia.

Meiosis•Meiosis is the division of

diploid cells into haploid cells in order to create sex cells.

• In meiosis the cell divides twice without a DNA replication between divisions. • This creates Gene Variation

which is what allows us to evolve as a species. The reason we get a

haploid cell is so that when the female and male sex cell fuse we have 46 chromosomes instead of 92 if both cells were diploid

Homologous Chromosomes

• Pairs of chromosomes that code for the same gene but might have different alleles.

For example: you can have two chromosomes that code eye color but one might code for blue eyes, the other for brown eyes.

• Homologous chromosomes cross over during division causing the genetic variation.

• Two chromosomes that code for the same gene switch genetic code by tangling with one another and keeping the code of the other.

Works Cited Page • http://www.ndsu.edu/pubweb/~mcclean/plsc431/eukarychrom/eukaryo3.htm• http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/cellhlabel.gif• http://www.dna-sequencing-service.com/wp-content/uploads/2010/06/gene-dna.jpg• http://www.anoleannals.org/wp-content/uploads/2011/04/sequencing-of-dna1.jpg• http://www.ibguides.com/biology/notes/chromosomes-genes-alleles-and-mutations• http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation5.html• http://

highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter11/animation_quiz_3.html

• http://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.mov• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/anima

tion__how_meiosis_works.html