Biology Unit 1 Flashcards
Describe the structure of a nucleotide of DNA
Each base is attached to a phosphate molecule and a deoxyribose sugar molecule to form a nucleotide of DNA
What is the structure of nucleotides?
They join together in an anti-parallel structure to form a double-stranded helix
What type of bonds holds nucleotides together?
Strong covalent bonds
Describe the complementary base pairs and their properties
DNA bases only join with their complementary base pairs. Adenine to Thymine and guanine to cytosine.
What bonds hold complementary base pairs together?
weak hydrogen bonds.
What bonds hold the sugar-phosphate backbones in place?
Strong sugar-phosphate bonds
Describe the structure of deoxyribose sugar in terms of carbon no.
It contains 5 carbon molecules.
What are prokaryotes?
Cells that don’t possess membrane-bound organelles such as a nucleus. They have a singular, circular chromosome and smaller circular plasmids.
What are eukaryotes?
Cells AKA eukarya, that possess membrane-bound organelles such as a nucleus. They have linear chromosomes in the nucleus and circular chromosome in the mitochondria and chloroplast.
What are some examples of eukaryotes & prokaryotes?
prokaryotes ( bacteria and archaea) eukaryotes (Plant and animal cells)
Describe the way in which linear chromosomes (DNA) are packaged in eukaryotes
A strand of DNA must be condensed and packaged in order to fit the nucleus. Molecules of DNA are tightly coiled and packaged around bundles of proteins called histones.
What is DNA replication?
The process by which a double helix of DNA makes an exact copy of itself. This occurs immediately before mitosis
What are the stages of DR in detail?
Stage 1: DNA unwinds and the weak hydrogen bonds break b/n the bases, allowing the 2 strands to unzip into 2 template strands.
Stange 2: The 2 template strands produce a y-shaped replication fork.
Stage 3: Since DNA polymerase can assemble DNA only in the 5’ to 3’ direction the new complementary strand to the 3’ to 5’ direction strand must be assembled in short 5’ to 3’ segments which are later joined by ligase.
What are leading strands?
Leading strands (3’ end)- complementary DNA nucleotides are added continuously to make one new strand.
What are lagging strands?
lagging strands(5’ end) - complementary nucleotides of DNA make fragments which must be joined to make a new strand.
What are primers?
primers are short complementary sequences of nucleotides that are required at the start of a new strand. They only bind to the 3’end to begin the making of a new complementary strand.
Describe the formation of a leading strand process
The enzyme DNA polymerase adds complementary nucleotides to synthesise a complementary strand continuously from 5’ to 3’.
Describe the formation of a lagging strand?
-The formation of a lagging strand is discontinuous. Several primers (which are required by DNA polymerase to work with) are added to the replication fork as the DNA
unwinds.
- DNA polymerase adds the free complimentary nucleotides in fragments. The fragments are joined together by the enzyme ligase.
How is the process of DR done efficiently and quick?
During DR, many replication forks are formed at the same time to ensure the whole chromosome is replicated quickly and efficiently. Each replicated DNA molecule is composed of one original strand and one new strand
What’s the function of DNA template in DR?
The original strands of DNA form a nucleotide for the new complementary strands.
What’s the function of DNA polymerase in DR?
an enzyme which adds free nucleotides to make a new complementary strand or fragment.
What’s the function of free DNA nucleotides in DR?
to make the new complementary strands.
What’s the function of primers in DR?
needed for DNA polymerase to bind to. the start point of a new complementary strand or fragment.
What’s the function of ATP in DR?
energy is required for DNA replication.