Intro to DNA I Flashcards
How does DNA store genetic information
DNA stores biological information in sequences of four bases of nucleic acid — adenine (A), thymine (T), cytosine (C) and guanine (G) — which are strung along ribbons of sugar- phosphate molecules in the shape of
How can DNA replicate itself without making mistakes?
Exonuclease,
Replicative DNA polymerases possess 3′ → 5′ exonuclease activity to reduce the misincorporation of incorrect nucleotides by proofreading during replication.
If there is an error it removes the nucleotides until error then is fixed
What causes the Two Groove sizes in a double helix
What are their names
Uneven twists head to two sizes of grooves
Major Groove
Minor Groove
What is the use of the Grooves in a DNA double Helix
Grooves permit proteins to bind to DNA and control its function (eg transcription)
What is Purine
There are two main types of purine:
Adenine and Guanine. Both of these occur in both DNA and RNA.
What is Pyrimidines
There are three main types of pyrimidines, however only one of them exists in both DNA and RNA: Cytosine. The other two are Uracil, which is RNA-exclusive, and Thymine, which is DNA-exclusive.
What do Genes code for
Most genes code for proteins
Some code for molecules of RNA
Where are Genes located
Genes are located on chromosomes with a specific
“address”
How many Genes does a human have
Humans have around 25,000 genes
What is a Genome
the complete set of genes or genetic material present in a cell or organism.
(The genome contains the entire DNA sequence)
How many chromosomes does a person have
Each person has 46 chromosomes (2 x 22 autosomes) + X&Y or X&X
What does diploid mean
A diploid cell has two complete sets of chromosomes.
How many Genes are in the Y chromosome
Y chromosome is much smaller (70 – 200 genes)
How many genes in the X chromosome
X (is larger) chromosome 900 – 1600 genes
What is inside the X and Y Chromosome
-Contain pseudoautosomal regions (PAR)
and
-genes needed for sex determination,
similar on X and Y
What is SRY
(Sex-determining region on the Y protein)
- initiates male sex determination. Starts seminiferous tubule development.
- Needed to produce sperm in the Testis
On Average how much DNA has to fit into a cell
On average about ~ 2 metres of DNA fits into a 6 µM cell
What is HeteroChromatin
What is its appearance under an electron microscope?
-Heavily Condensed Chromosome
-Usually occurs when the activity of the genes is modified or suppressed.
-Appears Darker under an electron microscope
What is Euchromatin
What is its appearance under an electron microscope?
- Unwounded, Less condensed Chromosome
- Often shows where genes are under active transcription
- Lighter colour under an electron microscope
What is DNA wound around
DNA is wound around histone proteins
How do histones and DNA bind
Histones are made from different proteins called Octomers
These have a positive charge
This allows it to bind to the negatively charged DNA
What is a histone core
How many base pairs does the histone core bind to
Histone core is an octamer
that binds about 147 bp (base pairs) of DNA
What is a Solenoid
A solenoid is a secondary structure that compacts DNA into the nucleus
What is the Diameter of the solenoid
30nm diameter
When is DNA unwound
DNA has to be unwound to be copied during mitosis
(cell division)
What is the structure of DNA and RNA
DNA and RNA are nucleic acids = polynucleotides,
(linear polymers of nucleotides)
What is the difference between a nucleoside and a nucleotide?
Nucleosides contain only sugar and a base
Nucleotides contain sugar, a base and a phosphate group
What is the difference between Ribonucleic Acid and Deoxyribonucleic acid
Ribonucleic Acid has a hydroxy group - RNA
Deoxyribonucleic acid has a hydrogen group - DNA
What are the two types of Nitrogenous Bases and what is their structure
-Purine: Double Ring and has 9 members
-Pyrimidine: Single ring and has 6 members
Example of a
Base, Nucleoside, and Nucleotide in RNA
RNA
BASE- Adenine
NUCLEOSIDE - Adenosine
NUCLEOTIDE - Adenosine Monophosphate (AMP)
Example of a
Base, Nucleoside, and Nucleotide in DNA
DNA
BASE - Adenine
NUCLEOSIDE - Deoxyadenosine
NUCLEOTIDE - Deoxyadenosine monophosphate (dAMP)
How are nucleotides joined together
Nucleotides are joined by phosphodiester bonds
What are the district ends
The chain also has distinct ends: 5’ P and 3’ OH
