DNA AND CHROMOSOMES Flashcards
What is DNA composed of ?
2 polynucleotide chains twisted around each other in a double helix
what is the backbone of DNA composed of ?
pentosephosphate units ( which is why the DNA has a negative charge )
what does the 5’ end usually have ?
a phosphate group on the 5 carbon of its terminal sugar
what does the 3’ usually have?
a hydroxyl group on the 3 carbon of its terminal sugar
what links the nucleotides of the DNA ?
phosphodiester bonds
how do the 4 nitrogen bases bind together ?
adenine binds to thymine by double hydrogen bond while cytosine binds to guanine with triple hydrogen bonds
what sugar does DNA contain and what sugar does RNA contain
deoxyribose
ribose
what are the 2 categories of nitrogenous bases?
purines ( double rings )
adenine
guanina
pyrimidines (single rings )
thymine
cytosine
uracil
whaat takes the place of thymine in RNA?
uracil
how is the double helix structure of the DNA maintained /?
is maintained by intra strand base stacking interactions
what are some causes of DNA denaturation
high temperature , low salt and high pH
what is a gene ?
sequence of nucleotide that encodes of the synthesis of gene products during gene expression
what does a chromosome refer to?
level of packaging from the DNA molecule to the chromosomal structure. linear DNA is packed into chromosome which is commonly called the packaging material .
what does diploid cell mean?
it means that the cell contains 2 sets of chromosome . 1 inherited from each parent .they contain 23 pairs of chromosomes . these 2 sets of chromosomes are referred too as homologous chromosomes
what is a haploid cell?
gametic chromosome that is found in sperm and egg and contain single copy of each chromosome
what is chromatin ?
DNA wrapped around histones
what is the structural entity of chromatin called?(single histone wrapped with DNA )
nucleosomes
what are the parts of a chromosome ?
short arm (P arm) long arm (Q arm) centromere telomere origin of replication (multiple) sister chromatids
when can the x structure of chromosome be seen?
during metaphase of cell division when chromosomes duplicate and are joined by centromere
what is the centromere ?
specialized DNA sequence (repetitive) .
what does the telomere do?
it protects the ends of chromosomes from deterioration and prevents the fusion of neighboring chromosome .
what are the 2 major categories of chromatin and how do they differ?
euchromatin
: less condensed regions of chromosomes
transcriptionally active
regions where 30 nm fibers forms radical loop domains
heterochromatin : tightly compacted regions of chromosomes
transcriptionally inactive
radical domains compacted even further
