Chromosomes

Yesterday and today we covered pages 202-219 and 233-245 in chapter 4. We talked mostly about chromosomes, how they are composed, what are their main features, how they are studied and how they are used to study the genomes of some organisms.

Reading for next week: pages 245-260

Quiz # 6 Q&As:

1. What are the three main components of a nucleotide?
Nitrogenous base, phosphate group, sugar

2. Why are the ends of a DNA strand called 5’ and 3’?
Carbons 5' and 3' in the sugar of a nucleotide are the ones that form covalent bonds with other nucleotides. At the ends of a DNA strand a 5' carbon (more exactly the phosphate group associated to it) and a 3' carbon will be open, and potentially ready to bind to another nucleotide.

3. What does it mean that DNA strands are antiparallel?
The 5' end of a strand matches up with the 3' en of the other

4. What does it mean that DNA strands are complementary?
Because the complementarity of the nitrogenous bases once you have the sequence of one strand of DNA you can infer the sequence of the complement.

The association between DNA and some proteins (mainly histones). They very basis of chromosomal structure and function.

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Quiz # 7 Q&As:

1. What are homologous chromosomes?
In diploid organisms they are pairs of chromosomes that have the same genes. One of the chromosomes is inherited from the father, the other from the mother.

2. What is a karyotype?
The organized set of chromosomes of a given organism. They are stained and homologous chromosomes paired so they can be studied.

3. What is a transposon?
A fragment of DNA that changes locations in a genome, or that it replicates it self so the copy can insert itself somewhere else in the genome.

4. Mention three kinds of transposons and explain one
LINEs, SINEs, repetitive sequences (miscrosatellites, minisatellites), retroviral - like sequences (explain either one of them)

5. What is the name of the histone complexes around which DNA wraps in the chromosomes?
Nucleosomes

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