Chromosomes, Genes, & DNA Flashcards
What is the structure of DNA?
Right-handed double helix
Major groove + minor groove
Sugar phosphate backbone + nitrogenous base pairs
Unpackaged = 2m long
What is the central dogma?
DNA ——————-> RNA ——————–> Protein
Genes ———————————————-> Protein
How is DNA packaged?
EUCHROMATIN ———> HETEROCHROMATIN
(exposed genes) (genes not expressed)
Scaffolding proteins
…………….
What is the definition of a gene?
Unit of inheritance and transcription. Length of DNA on a chromosome that codes for a protein (or RNA) and its transcription and translation located at fixed positions on chromosomes.
What is the definition of a genome?
Total genetic content of an organism
In a diploid organism, it is the DNA sequence of one set of chromosomes (haploid no.)
Humans: 22 autosomes + 2 sex chromosomes
What is the difference between nucleosides and nucleotides? What are the two types of pentose sugar, and what is the difference between them?
Nucleoside: sugar + base
Nucleotide: sugar + base + phosphate group (phosphate ester link)
Ribose (RNA): 2 OH groups
2-deoxyribose (DNA): 1 OH group
What are the two types of bases? How many hydrogen bonds are between the pairs?
PURINE: (2 rings)
Adenine & Guanine
PYRIMIDINE: (1 ring)
Cytosine & Thymine/Uracil
G - C = 3 H-bonds
A - T/U = 2 H-bonds
What is present at the 5’ and 3’ ends of the DNA?
5’ end = phosphate
3’ end = hydroxyl group
What is the definition of chromatin?
DNA + proteins + RNA needed to package DNA into cell nucleus
Loose = euchromatin Tight = heterochromatin
What are the important characteristics of the DNA code?
Universal = same triplet codons for same aa in all organisms
Triplet code = allows at least 20 possibilities (64 total)
Degenerate = aa can be coded for by more than one codon
Non-overlapping = no gaps in sequence
