Chapter 3: DNA Structure and function Flashcards
Where is DNA found in eukaryotes?
DNA occurs bound to proteins in chromosomes within the nucleus of eukaryotic cells and the nucleus is enclosed in a nuclear membrane to protect its interior.
Where is DNA found in prokaryotes?
DNA occurs as unbound circular DNA in the nucleoid region of the cytosol. the nucleoid region isn’t bound by a nuclear membrane, so the DNA is not contained.
Where else is DNA found in eukaryotes?
Unbound, circular dna is also found oin the mitochondria and chloroplasts of eukaryotic cells
What are nucleotides made up of?
A five-carbon (pentose) sugar known as deoxyribose sugar, a phosphate group and a nitrogenous base.
Simple definition of a nucleotide.
A nuceltoide is the basic structural unit of DNA.
Explain the structure of a nucleotide.
Each phosphate group is attached to 2 sugar molecules by ‘ester’ bonds and is then called a phosphodiester bond.
Explain the ester bonds within nucleotides.
The five carbon atoms in each sugar moplecule which form a ring, are numbers 1’ to 5’. one of these ester bonds is formed with hte 3’ carbon of one sugar ring and the other is formed with hte 5’ carbon of the next ring.
What is the sugar-phosphate backbone?
The chain of alternating sugar molecules and phosphate groups is called the sugar-phospate backbone.
How is the structure of RNA different to that of DNA?
RNA has a similar structure to DNA, expect deoxyribose sugar is replaced with ribose sugar.
What is a strand of nucleotides directionally described?
Using the phase 5’ to 3’. the 5’ end starts with a phosphate and the 3’ end finishes with a sugar. DNA & RNA synthesis occurs in the 5’ to 3’ direction.
Describe the structure of the DNA molecule?
The shape of DNA molecule is a double helix. the term ‘dobule’ refers to the two strands, which are joined by the weak hydrogen bonds between complementary pairs of nitrogenous bases. talk about complementary base pairing then talk about what the term ‘helix’ means.
What does complementary base pairing mean?
Adenine always pairs with thymine, and cytosine always pairs with guanine.
What does the term ‘helix’ mean in terms of the structure of the DNA molecule?
The term ‘helix’ describes the helical (spiral) molecular shape: the two linear strands run in opposite directions to each other (i.e. are anti-parallel) and are twisted into a helix.
Draw a dna molecule.
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What is a gene?
A section of DNA that codes for a species protein (or polypeptide).
Is DNA important in relation to genetics?
Genes may code for more than one kind of polypeptide, and that genes intewract with one another, causing changes in their expression, DNA therefore controls the growth and developement of an organism
Is DNA important in relation to genetics?
Genes may code for more than one kind of polypeptide, and that genes intewract with one another, causing changes in their expression, DNA therefore controls the growth and developement of an organism
Why does DNA enable certain traits to be passed on to the next generation?
Because it carries information coded in the segments of its molecule known as genes.
Why does the structure of DNA allow DNA replication to occur?
The structural properties of the DNA molecule: its nucleotide composition, paring and hydrogen bonding; and the fact that DNA strands can function as template strands.
Describe the structure of the DNA molecule in a simple way.
The DNA helix is a double-stranded molecule. the two strands are held together by hydrogen bonding between complementary nitrogenous bases
As well as nitrogenous bases, nucleotides have a sugar-phosphate backbone, in which the sugar molecules are linked by phosphodiester bonds.
What is the product of DNA replication?
Two identical, double-helix DNA molecules, each consisting of one parental strand and one new strand.
When does DNA replication occur?
During the S phase of interphase during the cell cycle.
Why is DNA replication referred to as semi-conservative?
Because one of the two strands is conserved, or retained, from one generation to the next, while the other strand is new.