Genetics Robinson CH.2
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What determines variation within species?
- -Different forms (alleles) exist for the different genes
- -species have their own specific set of alleles
The set of alleles that an individual possesses
What are phenotypes?
Alleles that individually represent messages for specific proteins that generate expressible traits
What is a genome?
The complete set of DNA possessed by an individual
Eukaryotes contain most of their DNA in the form of...
chromosomes found in their nuclei, but they also contain DNA in mitochondria and chloroplasts (plants).
monomers bound together into long polymers
Nucleotides consist of...
a five carbon sugar (deoxyribose), a phosphate and a nitrogenous base.
Four different bases are in DNA:
Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). The first two are purines, the latter two are pyrimidines. Uracil (U) replaces Thymine in RNA and is a pyrimidine also.
the 5' carbon is where the ____ attaches and the 1' carbon is where the ____ attaches.
- nitrogenous base
A sugar phosphate backbone is....
generated by phosphodiester bonds forming between the phosphate of one nucleotide and the 3' carbon belonging to the sugar of an adjacent nucleotide.
The two sugar phosphate backbones assume an ______ orientation.
A _____ is a region of DNA capable of being transcribed to produce a functional RNA molecule at the correct time and in the correct place.
A _______ must be associated with each gene allowing it to be activated.
At the other end of the gene there must be a _____.
Most eukaryotic genes contain______that must be excised from the RNA prior to rejoining the______and forming a functional message.
- Eukaryotic Nuclear
Plasmid Genome are...
- typically circularized DNA found in bacteria, apart from the primary bacterial DNA.
- Usually have genes and an origin for replication.
- Multiple copies per cell is common.
Organellar genome are...
- DNA in mitochondria and chloroplasts.
- Several copies are typical per organelle.
- DNA is usually in a circular configuration.
Virus Genome are...
- a protein coat surrounds the genomic core.
- The genome can consist of single or double stranded RNA or DNA depending on viral type.
Prokaryotic Genome are...
- Usually a single, closed, circular DNA.
- Functionally related genes are often adjacent to each other forming groups called operons that are turned on or off simultaneously.
- The DNA is concentrated in the nucleiod, which is not membrane bound.
- Non-histone proteins are associated with the DNA for packing it.
Eukaryotic Nuclear genome are...
- One continuous double stranded DNA molecule together with associated histone and non-histone proteins forms an individual chromosome.
- A single set of all the different types of chromosomes in an organism is referred to as the haploid genome.
- Species typically have a specific number of sets of chromosomes (their ploidy). Those with one set are haploid, two diploid, three triploid, etc.
A karyotype is a...
- picture of all of the chromosomes of an organism arranged in homologous pairs according to decreasing size.
- These arrangements are facilitated by the location of the centromeres of the chromosomes.
The centromere is a...
contracted region of the chromosome necessary for attachment of microtubules during Mitosis and Meiosis.
Chromosome ends are referred to as _____.
Bands may appear when Chromosomes are stained following chemical treatment. Depending on the procedure these bands may reflect regions of high compaction (_____) or low compaction (____).
Two other physical landmarks that exist are nucleolar organizing regions(NOR) and chromomeres.
- The NOR is the portion of the DNA where the message for rRNA resides and ribosomes are assembled in the surrounding volume Fig 2-16.
- Chromomeres are beadlike thickenings that appear along the DNA early during nuclear division.
In eukaryotes, DNA has associated with it histone proteins that organize it into _____.
- Nucleosomes are octamers of 4 types of histones (H2A, H2B, H3, and H4).
- DNA wraps around this octamer 2 times (like thread on a spool) producing the nucleosome that is 10nm in diameter.
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