DNA and Chromosomes Flashcards
(26 cards)
What is a function of the protein component of chromosomes?
It packages the DNA strands.
Chromosomes are made up of protein and DNA. The DNA carries the genetic information, and the protein component helps store the long DNA molecules in the cell, in addition to controlling access to the DNA molecules.
When Griffith injected heat-killed infectious bacteria mixed with live harmless bacteria, he found that the mice died because
the live harmless bacteria were transformed into infectious bacteria.
Griffith found that heat-killed infectious bacteria alone or live harmless bacteria on their own were NOT able to infect and kill the mice. However, when he mixed the two together, the mice died and an infectious strain of bacteria was found in the blood of the mice.
The type of bond that holds together neighboring subunits in a single strand of DNA is a
phosphodiester bond.
DNA is a long polymer of nucleotides held together by phosphodiester bonds. This forms a single strand of DNA. The two strands of DNA are held together by hydrogen bonds between the nucleotide bases.
The consistent diameter of the DNA double helix arises because of which property?
base pairing of pyrimidines with purines
DNA is made of up two strands where purines bases (1 carbon ring) pair with pyrimidines (2 carbon rings). If purines and purines base-paired, or pyrimidines and pyrimidines base-paired, the helix would be wider or narrower (respectively) along its length due to the different sizes of the base combinations.
If one end of a DNA strand has a phosphate group on it, the chemical group on the other end must be
hydroxyl
The hydroxyl group and the phosphate group of neighboring nucleotides bond together during DNA polymerization, which leads to a polarity of the DNA strand. One end has a phosphate group, the other end has an unbound hydroxyl group.
The part of the DNA molecule that carries the information for producing proteins is
the order of the nucleotide bases.
The linear sequence of the nucleotide bases in the DNA molecule is what contains the information for making proteins. This is decoded by other molecules that translate this information to link specific amino acids into proteins.
The structural feature of DNA that hints at the mechanism for its replication is the
complementary base pairing.
The complementary base pairing of A with T and G with C suggests that one strand could be used to make a new copy of the other strand. Although the other answers are features of DNA, they do not directly produce a way for the molecule to be copied.
Which of the following is found only in eukaryotic genomes, and NOT in prokaryotic genomes?
telomeres
Prokaryotic DNA has the same chemical structure as eukaryotic DNA and is packaged by proteins to fit in the cell. Prokaryotes, however, usually have a single circular chromosome, and therefore no telomeres, which are the specialized sequences at the ends of linear chromosomes.
The technique whereby human chromosomes are stained and identified is called a
karyotype.
Scientists can stain chromosomes from a human tissue sample in order to identify all the chromosomes. Identification is done from the staining pattern or by using chromosome sequence-specific fluorescent dyes and can be helpful in identifying abnormalities in the size, number, or sequence rearrangement of chromosomes.
___________ is a sequence of DNA that contains the information required for making a particular functional RNA or protein.
A gene
A gene is a segment of DNA that has the instructions for making an RNA or protein. The genome is the total amount of genetic information carried in the complete set of chromosomes in an organism.
What is the relationship between genome size and organismal complexity?
More complex organisms generally have larger genomes but there are many notable exceptions.
More complex organisms have more functions requiring specialized proteins and RNA and thus generally have more genes and larger genomes. However, there are many exceptions to this rule, as many plants and a particular amoeba have much larger genomes than humans.
Which specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes?
centromeres
Centromeres are a sequence of DNA upon which specialized structures are formed to allow the mitotic spindle machinery to attach to each sister chromatid of a duplicated chromosome.
What is a function of the nucleolus?
to assemble ribosomal RNA and proteins into ribosomes
The nucleolus is an organization of chromosomal regions that contain genes for ribosomal RNAs. These RNAs are transcribed in the nucleolus and are assembled with ribosomal proteins to make ribosomes.
When are chromosomes in their most compacted form?
during mitosis.
During mitosis, the chromatin structure that packages chromosomes gets even more compacted than usual. This is to compress the chromosomes into discrete bodies that are easier to separate and organize.
What types of bonds are formed between histone proteins and DNA to form nucleosome core particles?
electrostatic interactions
Histone proteins are highly positively charged due to their composition from a large number of basic amino acids. This allows them to interact with the negatively charged DNA backbone.
How does methylation of histone tails affect the accessibility of DNA?
It can have different effects depending on the location.
The addition of methyl groups to modify histone tails can have various effects on the chromatin structure, depending on the histone protein modified and location in the protein. These histone modifications recruit different regulatory proteins and do not have a direct effect on the chromatin themselves.
Heterochromatin can spread along a chromosome until it encounters a
barrier DNA sequence.
Heterochromatin spreading can occur when histone-modifying complexes bind to the mark they catalyze and establish the modification in neighboring histones. Barrier sequences function to block neighboring histones from the modification activity and stop the spread of heterochromatin.
What can happen if heterochromatin spreads inappropriately into an area with active genes?
The active genes can become silenced.
Due to its compact nature, genes in heterochromatin are often inactive because they are not accessible. Heterochromatin can sometimes accidentally spread into regions where it is not meant to and cause silencing of genes in that region.
Wat is het lot van een cel die zijn kern uitstoot of verliest? Noem een menselijke cel die geen kern heeft.
Heeft beperkte levensduur (3-4 maanden). Kan niet repliceren. Geen mRNA maken om eiwitten te maken, dus als enzymen en celstructuur beginnen af te brokkelen dan geen vervanging mogelijk. Bijv. rode bloedcel
Wat is het genoom van een organisme?
Het genoom van een organisme is de volledige DNA sequentie van het organisme
Het DNA van twee verschillende diersoorten kan vaak worden onderscheiden door een verschil in de:
ratio van A + T tot G + C, want G en C zijn in vaste verhouding tot elkaar en A en T ook, maar G:C en A:T kunnen sterk verschillen.
In welke fase van de celcyclus zijn de individuele chromosomen zichtbaar te maken met behulp van lichtmicroscopie?
Mitose
Wat is een gen?
Een gen is een stuk DNA dat codeert voor een eiwit (of soms functioneel RNA)
Tijdens welke fase van de celcyclus wordt DNA gesynthetiseerd?
S-fase (onderdeel van interfase)
