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Test: MCAT Biology
Human chromosomes are divided into two arms, a long q arm and a short p arm. A karyotype is the organization of a human cell’s total genetic complement. A typical karyotype is generated by ordering chromosome 1 to chromosome 23 in order of decreasing size.
When viewing a karyotype, it can often become apparent that changes in chromosome number, arrangement, or structure are present. Among the most common genetic changes are Robertsonian translocations, involving transposition of chromosomal material between long arms of certain chromosomes to form one derivative chromosome. Chromosomes 14 and 21, for example, often undergo a Robertsonian translocation, as below.
A karyotype of this individual for chromosomes 14 and 21 would thus appear as follows:
Though an individual with aberrations such as a Robertsonian translocation may be phenotypically normal, they can generate gametes through meiosis that have atypical organizations of chromosomes, resulting in recurrent fetal abnormalities or miscarriages.
| 7. | Histones are important components of chromosomes that help to form the scaffolding around which DNA wraps while organizing. Considering the structure of DNA, what is most likely true of histones? |
Histones interact with DNA mainly through covalent interactions
They are basic proteins and undergo acetylation to vary DNA binding
They are acidic proteins because DNA is generally negatively charged
Histones are fixed structures, and associated with DNA in every phase of the cell cycle
They are neutral proteins and interact with DNA via van der Walls forces
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