Chromosomes, Genes and DNA Flashcards
Where are genes found?
On chromosomes in nucleus
What do genes produce?
Proteins
Where are proteins produced?
In the cytoplasm
What is the passage from gene to protein?
DNA → RNA → protein
How does DNA in the nucleus differ in appearance?
NAME?
When is the DNA in chromosomes?
When its dividing
How many chromosomes are there in humans?
46
What is chromatin?
DNA in the nucleus
What are the two types of chromatin?
- Heterochromatin
- Euchromatin
What is the more condensed form of chromatin?
Heterochromatin
What shape is DNA?
Double helix
What feature does the double helix of DNA have?
Has a major groove and minor groove
What is the aim of the human genome project?
To find cures for diseases
What do we want to know about the human genome?
What the sequence actually does
What has been found about the functionality of the human genome?
That 70-80% of the human genome has function
What is the smallest unit of DNA packaging?
The nucleosome
What is a nucleosome?
DNA wrapped around a histone core
What is between histones?
Bits of DNA
What are the bits of DNA between histones called?
Linker DNA of nucleoosme
What do the histone cores consist of?
Lots of protein
What can happen if the protein complexes in histone cores go wrong?
Can result in disease
Is DNA flexible or rigid?
Flexible
Where can DNA flex?
In the minor groove
What is the result of the flexibility of DNA?
It can wrap around the histone core twice
How are nucleosomes further packaged?
Into solenoids
What is heterochromatin made up of?
Solenoids
Are genes expressed in heterochromatin?
No
Why are genes not expressed in heterochromatin?
Because they are too tightly bound to access
How does euchromatin differ from heterochromatin?
It has a different density, and so the genes are expresseed
What do solenoid loops form?
Chromatids of chromosomes
What are the chromatids called?
NAME?
Are genes expressed in chromosomes?
No
Why are genes not expressed in chromosomes?
Because the DNA is so tightly wound to get into package that it can’t be
What to genes carry?
The code for protein
What does each gene have?
A chromosomal location
What is meant by a chromosomal location?
On a certain position on a chromosome on DNA molecule is the code for a certain protein
How do chromosomal locations differ between individuals?
They don’t
What does each chromosome have?
A different banding pattern
Where is the chromosomal banding pattern visible?
Under the microscope
What is the human genome?
The entire DNA sequence
What makes up the 24 different chromosomes?
22 pairs, and the sex chromosomes (X and Y)
What are autosomes?
Non-sex chromosomes
How are chromosomes numbered?
In size order, apart from 21 and 22, which are the wrong way round
What are genes on the Y chromosome limited to?
Male specific things
What are DNA and RNA?
Nucleic acids
What are nucleic acids?
Polynucleotides
What are polynucleotides made up of?
Linear polymers of nucleotides
What does a nucleoside consist of?
- Base
- Sugar
What does a nucleotide consist of?
- Base
- Sugar
- Phosphate
What are the two types of pentose sugar in nature?
NAME?
What does RNA contain?
Ribose sugar
What does DNA contain?
2-deoxyribose
What is a ribonucleotide?
A RNA building block
What does a ribonucleotide consist of?
NAME?
Where is the nitrogenous base bound?
To carbon 1 of the ribose sugar
What joins the phosphate group to the ribose sugar?
A phosphate ester link
Where does the phosphate group join to the ribose sugar?
Carbon 5
What charge does every nucleotide have?
Negative
What is the result of the negative charge on nucleotides?
Every DNA molecule is heavily negatively charged
What is the significance of the negatively charged DNA molecules?
They interact with the positively charged histones
What are the two types of nitrogenous bases?
NAME?
What does a purine have?
A 2 ring structure; a 5C and a 4C ring
What does a pyrimidine have?
1 ring
What are the two main purines in RNA and DNA?
NAME?
What are the main pyrimidines in RNA and DNA
NAME?
How are nucleotides joined together?
Phosphodiester bonds
What does the nucleotide chain have?
Polarity
In what direction does the nucleotide chain have polarity?
5’ to 3’
Why is the 5 prime end so named?
Because thats were the C5 from the nucleotide is
What is at the 5’ end?
Phosphate
What is at the 3’ end?
Hydroxyl
Where are phosphodiester bonds formed?
At the C5 phosphate → C3 hydroxyl
What base pairs are made?
- G-C
- A-U/T
What type of bonds form between base pairs?
Hydrogen
How many bonds form between G and C?
3
How many bonds form between A and U/T?
2
What structures can nucleic acids form?
Duplex
What happens to nucleic acids so base pairs can form?
They are flipped
What can be said of the nucleic acid strands that form duplex structures?
They are complementary and anti-parallel
Between what strand types can duplex structures be formed?
NAME?
Are duplex structures stable or temporary?
Can be either
Where does duplex structure formation occur?
Can be in vivo or in lab
What are RNA stem loops?
Single stranded RNA molecules that can form duplex structures within it’s own structure
How are RNA stem loops formed?
Hydrogen bonds are formed between antiparallel complementary sequences within the structure
Give an example of an RNA stem loop
tRNA
