6. Chromosomes, Genes and DNA Flashcards
Where are genes found?
On chromosomes in the nucleus.
Where are proteins found?
In the cytoplasm.
What are the two visible parts of a nucleus in electron microscopy?
Euchromatin and heterochromatin.
What is the 1st level of DNA packaging?
DNA wound around histone cores.
What is the 2nd level of DNA packaging?
Solenoids.
What are two differences between euchromatin and heterochromatin?
Euchromatin are the beads on a string, histone cores and genes are expressed. But heterochromatin is the solenoid fibres and the genes are not expressed.
Are genes expressed in a chromosome?
No, because it is made of heterochromatin.
How many genes do humans have?
25,000.
What is the human genome?
The entire DNA sequence of humans, the 24 chromosomes including 2 sex chromosomes.
What is a base and sugar together called?
A nucleoside.
What is a base, sugar and phosphate together called?
A nucleotide.
What are polynucleotides?
Linear polymers of nucleotides.
What are the two types of pentode sugar?
Ribose in ribonucleic acid and 2-deoxyribose in deoxyribonucleic acid.
What charge do DNA molecules have?
Negative.
What are the two types of nitrogenous bases and what are the key difference between their structures?
Purines and pyrimidine. Purines have two rings but pyrimidines only have one ring.
What are the two types of main purines?
Adenine and guanine.
What are the three types of main pyrimidines?
Cytosine, uracil and thymine.
For the following RNA bases name their nucleoside and nucleotide:
a. Adenine (A)
b. Guanine (G)
c. Uracil (U)
d. Cytosine (C)
a. Adenosine, adenosine monophosphate (AMP)
b. Guanosine, guanosine monophosphate (GMP)
c. Uridine, uridine monophosphate (UMP)
d. Cytidine, cytidine monophosphate (CMP)
For the following DNA bases name their nucleoside and nucleotide:
a. Adenine (A)
b. Guanine (G)
c. Thymine (T)
d. Cytosine (C)
a. Deoxyadenosine, deoxyadenosine monophosphate (dAMP)
b. Deoxyguanosine, deoxyguanosine monophosphate (dGMP)
c. Deoxythymidine, deoxythymidine monophosphate (dTMP)
d. Deoxycytidine, deoxycytidine monophosphate (dCMP)
What joins nucleotides?
Phosphodiester bonds.
How do base pairs join?
By hydrogen bonds: C=G (triple) and A=T.
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What three duplex structures can be formed from DNA and RNA?
DNA-DNA, DNA-RNA, RNA-RNA.
Give an example of a unit where RNA stem-loops can be found.
tRNA.
Describe the DNA double helix.
Two alpha chains, anti parallel, right handed twist.
